✅Class 11: Biology

Section 1 - Diversity in the Living World

Chapter 1 - The Living World

Introduction

1. Marvels of the Living World

Diversity: Wide range of living organisms in various habitats like mountains, forests, oceans, lakes, deserts, and hot springs.

Examples of Natural Beauty are galloping horses, migrating birds, valleys of flowers, and sharks.

2. Ecological Aspects

Interactions: Conflict and cooperation within populations and communities.

Cellular Level: Molecular activities inside a cell.

3. Understanding Life

Technical Aspect: Differentiating living from non-living entities.

Philosophical Aspect: Purpose of life (not addressed in scientific discussions).

Scientific Focus: Exploration of what constitutes 'living'.

Diversity in the Living World

1. Biodiversity: The Variety of Life

Diverse Life Forms: Includes plants, insects, birds, aquatic life, and microscopic organisms.

Species Count: Known species range between 1.7 to 1.8 million.

Continuous Discovery: New species are being identified regularly.

2. Nomenclature and Identification

Standardization: Universal process of naming organisms for global understanding.

International Codes: ICBN for plants, ICZN for animals.

Binomial Nomenclature: System by Carolus Linnaeus with two parts - Generic name and specific epithet (e.g., Mangifera indica).

3. Rules of Naming

Latin Names: In italics or underlined when handwritten.

Genus and Species: Genus with a capital letter, species with a lowercase letter.

Author Citation: Indicates the scientist who first described the species.

4. Classification and Taxonomy

Classification: Grouping organisms based on observable characteristics into taxa.

Taxonomy: Involves characterisation, identification, classification, and nomenclature.

Systematics: Studies evolutionary relationships among organisms.

5. Historical and Modern Context

Early Classifications: Based on utilitarian perspective.

Modern Taxonomy: Integrates morphology, ecology, cell structure, development for classification.

Taxonomic Categories

1. Taxonomic Categories and Hierarchy

Hierarchy of Steps: Classification involves a series of steps, each representing a taxonomic category.

Taxon: A singular unit of classification, multiple taxa form the hierarchy.

Example: Insects as a group share common features, constituting a taxonomic category.

2. Taxonomic Groups/Categories

Common Categories: Include kingdom, phylum/division (plants), class, order, family, genus, and species.

Species: The lowest and most specific taxonomic category.

3. Placement in Categories

Character Knowledge: Essential for categorizing organisms.

Identification Process: Involves recognizing similarities and differences among individual organisms or groups.

Species

1. Understanding Species in Taxonomy

Definition of Species: A group of individual organisms with fundamental similarities.

Distinguishing Species: Identification based on distinct morphological differences.

Examples:

Mangifera indica: 'indica' is the species; 'Mangifera' is the genus.
Solanum tuberosum (Potato): 'tuberosum' is the species; 'Solanum' is the genus.
Panthera leo (Lion): 'leo' is the species; 'Panthera' is the genus.

Species Within a Genus: A genus can have multiple species with morphological similarities (e.g., Panthera leo and Panthera tigris).

2. Human Species Classification

Species: sapiens.

Genus: Homo.

Scientific Name: Homo sapiens.

Genus

1. Understanding the Genus in Taxonomy

Definition of Genus: A category that includes groups of related species with more common characteristics than species from other genera.

Characteristics of Genus: Represents aggregates of closely related species.

Examples:

Solanum: Potato (Solanum tuberosum) and Brinjal (Solanum melongena) are different species of the same genus.
Panthera: Includes species like Lion (Panthera leo), Leopard (Panthera pardus), and Tiger (Panthera tigris).

Genus Distinction: Panthera (lions, leopards, tigers) is distinct from Felis (cats) despite some common features.

2. Role of Genus in Classification

Intermediate Taxonomic Rank: Falls between species and family in the classification hierarchy.

Function: Helps in organizing closely related species, facilitating easier study and reference.

Family

1. Understanding the Taxonomic Category 'Family'

Definition: A category higher than a genus, grouping together related genera based on less number of similarities.

Characteristics: Identified based on both vegetative and reproductive features, particularly in plants.

Plant Example: The family Solanaceae includes different genera like Solanum, Petunia, and Datura.

Animal Example: The family Felidae comprises genera such as Panthera (lions, tigers, leopards) and Felis (cats).

Family Distinction in Animals: Cats (Felidae) and dogs (Canidae) are separated into different families based on their distinct features.

2. Role of Family in Classification

Taxonomic Position: Above genus and below order in the hierarchy of biological classification.

Function: Helps in a broader grouping of organisms, making it easier to study and understand their evolutionary relationships.

Order

1. Understanding the Taxonomic Category 'Order'

Definition: A higher taxonomic category than the family, grouping together several families based on fewer similar characteristics.

Character Basis: Orders and other higher categories are identified based on aggregates of characters.

Plant Example: Plant families like Convolvulaceae and Solanaceae are grouped into the order Polymoniales, mainly based on floral characteristics.

Animal Example: The order Carnivora includes families such as Felidae (cats) and Canidae (dogs).

2. Role of Order in Classification

Taxonomic Position: Above family and below class in the biological classification hierarchy.

Function: Facilitates the grouping of organisms into broader categories, aiding in understanding evolutionary relationships and biological organization.

Class

1. Understanding the Taxonomic Category 'Class'

Definition: A taxonomic category higher than the order, which groups together related orders.

Example: The class Mammalia includes the order Primata (monkeys, gorillas, gibbons) and Carnivora (tigers, cats, dogs), among others.

2. Role of Class in Taxonomic Hierarchy

Taxonomic Position: Situated above the order and below the phylum in the biological classification system.

Function: Facilitates the organization of a wide range of orders under a more generalized group, reflecting broader evolutionary relationships and characteristics.

Phylum

1. Understanding the Taxonomic Category 'Phylum'

Definition: A higher taxonomic category that groups together several classes sharing key characteristics.

Example in Animals: Phylum Chordata includes classes like fishes, amphibians, reptiles, birds, and mammals, characterized by the presence of a notochord and a dorsal hollow neural system.

2. Role of Phylum in Taxonomic Hierarchy

Taxonomic Position: Above the class and below the kingdom in the biological classification system.

Function in Animals: Groups together various classes based on fundamental structural similarities and evolutionary links.

Equivalent in Plants: In the botanical classification, similar classes are grouped into a division, which is analogous to the phylum in zoological taxonomy.

Kingdom

1. Taxonomic Category: Kingdom

Definition:

The highest category in the biological classification system.

Groups all animals in Kingdom Animalia and all plants in Kingdom Plantae.

Characteristics:

Represents the most extensive level of classification.

Contains a vast array of organisms with fundamental similarities.

Hierarchy and Complexity:

Part of a hierarchy that starts from species and ascends to kingdom.

As we move up from species to kingdom, common characteristics among members decrease.

The higher the category, the broader and more diverse it becomes, increasing the complexity of classifying organisms.

2. Taxonomic Hierarchy and Challenges:

Arrangement Basis:

Organized based on shared traits and evolutionary relationships.

Lower taxa (like species, and genus) have more common features among their members.

Challenges in Higher Taxa:

Higher taxa (like kingdoms) encompass a wider range of organisms, making it challenging to determine relationships at the same level.

Classification complexity increases with ascending order in the hierarchy.

Summary

1. Overview of Taxonomy in the Living World

Diversity in Organisms:

The living world showcases a vast array of organisms varying in size, color, habitat, and physiological traits.

Role of Taxonomy:

Taxonomy is a scientific discipline focused on the identification, nomenclature, and classification of organisms.

It helps in understanding the diversity and characteristics of various species.

2. Taxonomic Processes and their Global Standards:

Identification and Naming:

Organisms are identified and named using a binomial system of nomenclature.

Each organism is given a two-word scientific name.

International Codes:

Taxonomy follows universally accepted codes for naming and classifying organisms.

3. Taxonomic Categories and Hierarchy:

Taxonomic Categories (Taxa):

Categories used for classifying organisms include species, genus, family, order, class, phylum/division, and kingdom.

Hierarchy in Classification:

These categories form a hierarchical structure, from specific (species) to general (kingdom).

Chapter 2 - Biological Classification

Introduction

1. Historical Overview

1.1. Early Attempts

Instinctive classification for practical uses like food, shelter, clothing.
Aristotle's classification: based on simple morphological characters.

Plants classified as trees, shrubs, herbs.
Animals divided based on red blood presence.

1.2. Linnaeus' Two Kingdom System

Plantae and Animalia kingdoms.
No distinction between eukaryotes/prokaryotes, unicellular/multicellular, photosynthetic/non-photosynthetic organisms.

2. Inadequacies of the Two Kingdom System

Many organisms didn't fit into Plantae or Animalia.

Emergence of criteria beyond gross morphology: cell structure, nutrition mode, reproduction, habitat, evolutionary relationships.

3. Whittaker's Five Kingdom Classification (1969)

3.1. Kingdoms Defined

Monera, Protista, Fungi, Plantae, Animalia.

3.2. Criteria for Classification

Cell structure, body organization, nutrition mode, reproduction, phylogenetic relationships.

3.3. Comparative Characteristics

Different characteristics of the five kingdoms.

4. Three-Domain System

Division of Monera into two domains.

Six kingdom classification including eukaryotic kingdoms.

5. Considerations in Classification

5.1. Kingdom Plantae

Early inclusion: bacteria, blue-green algae, fungi, mosses, ferns, gymnosperms, angiosperms.
Unified by cell wall presence.

5.2. Issues with Early Classification

Grouping of prokaryotic (bacteria, cyanobacteria) with eukaryotic organisms.
Unicellular and multicellular organisms grouped together.
Lack of distinction between heterotrophic (fungi) and autotrophic (green plants).
Changes in wall composition: fungi (chitin) vs. green plants (cellulose).

5.3. Kingdom Fungi

Separate kingdom due to distinct characteristics.

6. Recent Classifications

6.1. Kingdom Monera

Grouping all prokaryotic organisms.

6.2. Kingdom Protista

Unicellular eukaryotic organisms.
Groups organisms previously classified in different kingdoms.

6.3. Criteria Evolution

Reflects morphological, physiological, reproductive, and phylogenetic similarities.

7. Focus of Study in the Chapter

Characteristics of Kingdoms Monera, Protista, and Fungi.

Plantae and Animalia kingdoms discussed in subsequent chapters.

Kingdom Monera

1. Overview of Kingdom Monera

1.1. Composition

Solely consists of bacteria.

1.2. Abundance and Habitat

Most abundant micro-organisms.
Found in diverse habitats: soil, hot springs, deserts, snow, and deep oceans.
Extreme habitats: can survive where few other life forms can.
Exist as parasites on or inside other organisms.

2. Bacterial Categories Based on Shape

2.1. Coccus (pl.: cocci)

Spherical-shaped bacteria.

2.2. Bacillus (pl.: bacilli)

Rod-shaped bacteria.

2.3. Vibrium (pl.: vibrio)

Comma-shaped bacteria.

2.4. Spirillum

Spiral-shaped bacteria.

3. Bacterial Structure and Behavior

3.1. Simple Structure

Despite the simplicity, bacteria exhibit complex behaviors.

3.2. Metabolic Diversity

Extensive range of metabolic activities.

3.3. Autotrophic Bacteria

Synthesize their own food from inorganic substances.
Types of autotrophs:

Photosynthetic autotrophs: use sunlight.
Chemosynthetic autotrophs: use chemical energy.

3.4. Heterotrophic Bacteria

Depend on other organisms or dead organic matter for food.

Archaebacteria

1. General Characteristics of Archaebacteria

1.1. Unique Habitats

Inhabit extreme environments.
Examples: salty areas, hot springs, marshy areas.

1.2. Distinction from Other Bacteria

Different cell wall structure.
Adaptation for survival in extreme conditions.

2. Types of Archaebacteria

2.1. Halophiles

Thrive in extremely salty areas.

2.2. Thermoacidophiles

Live in hot springs.

2.3. Methanogens

Found in marshy areas.
Present in the gut of ruminants like cows and buffaloes.
Role in methane (biogas) production from animal dung.

Eubacteria

1. General Characteristics

1.1. Definition

Eubacteria are diverse 'true bacteria'.

1.2. Structural Features

Rigid cell wall.
Flagellum for motility (if present).

2. Types of Eubacteria

2.1. Cyanobacteria (Blue-Green Algae)

Contain chlorophyll a; photosynthetic autotrophs.
Forms: unicellular, colonial, or filamentous.
Habitats: freshwater/marine, terrestrial.
Gelatinous sheath around colonies.
Capable of forming blooms in polluted water.
Nitrogen fixation in heterocysts (e.g., Nostoc, Anabaena).

2.2. Chemosynthetic Autotrophs

Oxidize inorganic substances (nitrates, nitrites, ammonia).
Important in recycling nutrients (nitrogen, phosphorous, iron, sulphur).

2.3. Heterotrophic Bacteria

Most abundant; decomposers.
Beneficial in curd production, antibiotic production, nitrogen fixation in legumes.
Some are pathogens causing diseases (cholera, typhoid, tetanus, citrus canker).

3. Reproduction in Bacteria

3.1. Primary Method

Binary fission.

3.2. Under Unfavourable Conditions

Spore formation.

3.3. Sexual Reproduction

Primitive DNA transfer between bacteria.

4. Mycoplasma

4.1. Characteristics

Lack a cell wall.
Smallest living cells, can survive without oxygen.

4.2. Pathogenic Nature

Cause diseases in animals and plants.

Kingdom Protista

1. Overview of Kingdom Protista

1.1. Classification

Includes all single-celled eukaryotes.
The boundaries of this kingdom are not clearly defined.

1.2. Diversity in Perception

Different interpretations among biologists about classifying protists.

2. Categories within Protista

2.1. Chrysophytes

2.2. Dinoflagellates

2.3. Euglenoids

2.4. Slime Moulds

2.5. Protozoans

3. Characteristics of Protista

3.1. Habitat

Primarily aquatic.

3.2. Biological Link

Forms a connection with plants, animals, and fungi.

3.3. Cellular Structure

Well-defined nucleus and membrane-bound organelles.
Presence of flagella or cilia in some members.

4. Reproduction in Protista

4.1. Asexual Reproduction

4.2. Sexual Reproduction

Involves cell fusion and zygote formation.

Chrysophytes

1. Overview of Chrysophytes

1.1. Composition

Includes diatoms and golden algae (desmids).

1.2. Habitat

Found in both freshwater and marine environments.

2. Characteristics of Chrysophytes

2.1. Physical Nature

Microscopic and planktonic (float in water currents).

2.2. Photosynthesis

Most are photosynthetic.

2.3. Diatoms

Unique cell wall structure: two overlapping shells like a soap box.
Cell walls contain silica, making them indestructible.
Lead to the formation of diatomaceous earth through accumulation.

2.4. Diatomaceous Earth

Formed from billions of years of cell wall deposits.
Uses: polishing, filtration of oils and syrups.

3. Ecological Role of Diatoms

3.1. Primary Producers

Serve as chief producers in ocean ecosystems.

Dinoflagellates

1. General Characteristics

1.1. Habitat

Mostly marine and photosynthetic.

1.2. Color Variations

Appear in various colors: yellow, green, brown, blue, red.
Color depends on the main pigments in their cells.

2. Physical Structure

2.1. Cell Wall

Stiff cellulose plates on the outer surface.

2.2. Flagella

Two flagella: one longitudinal, the other transverse.
Located in a furrow between the wall plates.

3. Ecological Impact

3.1. Red Tides

Rapid multiplication, particularly of red dinoflagellates (e.g., Gonyaulax).
Can cause the sea to appear red.

3.2. Toxin Release

Large numbers release toxins.
Potential to kill marine life, including fishes.

Euglenoids

1. Habitat and Nature

1.1. Habitat

Primarily found in stagnant freshwater.

1.2. Flexibility

Lack a cell wall; possess a protein-rich layer called pellicle for flexibility.

2. Structural Features

2.1. Flagella

Possess two flagella: one short, one long.

3. Nutritional Behavior

3.1. Photosynthesis

Photosynthetic in presence of sunlight.

3.2. Heterotrophic Mode

Behave as heterotrophs in absence of sunlight; predating on smaller organisms.

4. Pigmentation and Example

4.1. Pigments

Pigments are identical to those in higher plants.

4.2. Example

Euglena.

Slime Moulds

1. Nature and Habitat

1.1. Classification

Slime moulds are saprophytic protists.

1.2. Behavior

Move along decaying twigs and leaves, engulfing organic material.

2. Plasmodium Formation

2.1. Under Favourable Conditions

Form a large aggregation called plasmodium.
Can grow and spread over several feet.

3. Fruiting Bodies and Spores

3.1. Under Unfavourable Conditions

Plasmodium differentiates to form fruiting bodies.
Fruiting bodies bear spores at their tips.

3.2. Spore Characteristics

Possess true walls; extremely resistant.
Can survive many years in adverse conditions.

4. Spore Dispersal

4.1. Method of Dispersal

Spores are dispersed by air currents.

Protozoans

1. General Characteristics of Protozoans

1.1. Nutritional Nature

All protozoans are heterotrophs.

1.2. Lifestyle

Live as predators or parasites.

1.3. Evolutionary Relation

Considered primitive relatives of animals.

Amoeboid protozoans

1. Habitat

1.1. Environmental Conditions

Found in fresh water, sea water, or moist soil.

2. Movement and Feeding

2.1. Pseudopodia

Move and capture prey using pseudopodia (false feet), as seen in Amoeba.

3. Physical Characteristics

3.1. Marine Forms

Possess silica shells on their surface.

4. Parasitic Nature

4.1. Examples of Parasites

Some amoeboid protozoans are parasites, e.g., Entamoeba.

Flagellated protozoans

1. General Characteristics

1.1. Lifestyle Variations

Members can be either free-living or parasitic.

1.2. Mobility

Characterized by the presence of flagella.

2. Parasitic Nature

2.1. Diseases Caused

Some parasitic forms are known to cause diseases like sleeping sickness.

2.2. Notable Example

Trypanosoma is a well-known parasitic flagellated protozoan.

Ciliated protozoans

1. Habitat and Movement

1.1. Habitat

Primarily aquatic organisms.

1.2. Movement

Actively moving due to thousands of cilia.

2. Feeding Mechanism

2.1. Gullet

Possess a cavity (gullet) that opens to the cell surface.

2.2. Cilia Function

Coordinated cilia movement steers water with food into the gullet.

3. Example

3.1. Notable Species

Paramoecium is a classic example of ciliated protozoans.

Sporozoans

1. Life Cycle Characteristic

1.1. Infectious Stage

Sporozoans have an infectious spore-like stage in their life cycle.

2. Notable Species and Impact

2.1. Plasmodium

The most notorious sporozoan.

2.2. Disease Caused

Causes malaria, a disease with a significant impact on the human population.

Kingdom Fungi

1. General Characteristics

1.1. Heterotrophic Nature

Fungi are heterotrophic organisms.

1.2. Morphology and Habitat

Diverse in form and habitat (e.g., bread mold, mushrooms).

1.3. Cosmopolitan Distribution

Found in air, water, soil, and living organisms.

2. Structure of Fungi

2.1. Physical Form

Mostly filamentous, except for unicellular yeasts.

2.2. Hyphae and Mycelium

Bodies consist of hyphae; a network of hyphae forms the mycelium.

2.3. Types of Hyphae

Coenocytic (multinucleated) and septate (with cross walls).

2.4. Cell Wall Composition

Made of chitin and polysaccharides.

3. Nutritional Modes

3.1. Saprophytes

Absorb nutrients from dead substrates.

3.2. Parasites

Depends on the living hosts.

3.3. Symbionts

Form symbiotic relationships (e.g., lichens, mycorrhiza).

4. Reproductive Modes

4.1. Vegetative Reproduction

By fragmentation, fission, and budding.

4.2. Asexual Reproduction

Via spores (conidia, sporangiospores, zoospores).

4.3. Sexual Reproduction

Involves oospores, ascospores, and basidiospores.

5. Sexual Cycle in Fungi

5.1. Steps in Sexual Reproduction

(i) Plasmogamy: Fusion of protoplasms.
(ii) Karyogamy: Fusion of nuclei.
(iii) Meiosis: Resulting in haploid spores.

5.2. Dikaryotic Phase

Intermediate dikaryotic stage (n + n) in some fungi.

6. Classification Criteria

6.1. Basis for Division

Mycelium morphology, spore formation, and fruiting bodies.

Phycomycetes

1. Habitat and Occurrence

1.1. Habitats

Found in aquatic environments, moist and damp areas.

1.2. Common Locations

Decaying wood, as parasites on plants.

2. Mycelium Characteristics

2.1. Type

Aseptate and coenocytic (multinucleate without septa).

3. Asexual Reproduction

3.1. Methods

By zoospores (motile) or aplanospores (non-motile).

3.2. Spore Formation

Spores produced endogenously in sporangia.

4. Sexual Reproduction

4.1. Zygospore Formation

Through the fusion of two gametes.

4.2. Gamete Types

Isogamous (similar morphology), anisogamous, or oogamous (dissimilar).

5. Examples of Phycomycetes

5.1. Notable Species

Mucor, Rhizopus (bread mold), Albugo (parasitic on mustard).

Ascomycetes

1. General Characteristics

1.1. Common Names

Known as sac-fungi.

1.2. Cellularity

Mostly multicellular (e.g., Penicillium), some unicellular (e.g., yeast Saccharomyces).

1.3. Nutritional Modes

Saprophytic, decomposers, parasitic, coprophilous (growing on dung).

2. Mycelium Features

2.1. Structure

Branched and septate mycelium.

3. Asexual Reproduction

3.1. Spore Type

Conidia (asexual spores).

3.2. Spore Formation

Produced exogenously on conidiophores.

3.3. Germination

Conidia germinate to produce mycelium.

4. Sexual Reproduction

4.1. Ascospores

Sexual spores produced endogenously in asci.

4.2. Fruiting Bodies

Asci arranged in ascocarps (types of fruiting bodies).

5. Notable Examples and Uses

5.1. Examples

Aspergillus, Claviceps, Neurospora.

5.2. Scientific Use

Neurospora used in biochemical and genetic work.

5.3. Edible Members

Morels and truffles are delicacies.

Basidiomycetes

1. General Characteristics

1.1. Common Forms

Includes mushrooms, bracket fungi, and puffballs.

1.2. Habitats

Found in soil, on logs, on tree stumps, and as parasites in living plants (e.g., rusts, smuts).

2. Mycelium Features

2.1. Structure

Branched and septate mycelium.

3. Reproduction

3.1. Asexual Reproduction

Rare; mainly vegetative reproduction by fragmentation.

3.2. Sexual Reproduction

Absence of sex organs.
Plasmogamy occurs by the fusion of vegetative cells of different strains.
Formation of dikaryotic structure leading to basidium.
Karyogamy and meiosis in basidium produce basidiospores.

3.3. Basidiospores and Basidia

Basidiospores are produced exogenously on basidia.
Basidia are arranged in fruiting bodies called basidiocarps.

4. Notable Examples

4.1. Examples

Agaricus (mushroom), Ustilago (smut), and Puccinia (rust fungus).

Deuteromycetes

1. Common Name and Classification

1.1. Known As

Commonly called imperfect fungi.

1.2. Classification Basis

Classified based on the known asexual or vegetative phases.

2. Discovery of Sexual Forms

2.1. Re-classification

When sexual forms discovered, moved to appropriate classes (ascomycetes or basidiomycetes).

2.2. Different Names for Stages

Asexual stage named and classified under deuteromycetes; sexual stage under other classes.

3. Reproductive Characteristics

3.1. Asexual Reproduction

Reproduce only by asexual spores (conidia).

3.2. Mycelium Structure

Mycelium is septate and branched.

4. Ecological Role and Examples

4.1. Nutritional Modes

Include saprophytes, parasites, and decomposers.

4.2. Contribution to Mineral Cycling

Decomposers of litter, aiding in mineral cycling.

4.3. Examples

Alternaria, Colletotrichum, Trichoderma.

Kingdom Plantae

1. Basic Characteristics

1.1. Composition

Includes all eukaryotic, chlorophyll-containing organisms (plants).

1.2. Cell Structure

Eukaryotic structure with prominent chloroplasts.
Cell walls primarily made of cellulose.

2. Nutritional Diversity

2.1. Mainly Autotrophic

Majority are autotrophic.

2.2. Partially Heterotrophic

Some members like insectivorous plants (Bladderwort, Venus fly trap) and parasites (e.g., Cuscuta).

3. Classification within Plantae

3.1. Major Groups

Includes algae, bryophytes, pteridophytes, gymnosperms, and angiosperms.

4. Life Cycle: Alternation of Generations

4.1. Two Distinct Phases

Diploid sporophytic and haploid gametophytic phases.

4.2. Variation Among Groups

Lengths of phases and their independence vary among plant groups.

Kingdom Animalia

1. Fundamental Characteristics

1.1. Type of Organisms

Heterotrophic eukaryotic organisms.

1.2. Cellular Structure

Multicellular with no cell walls.

1.3. Dependency for Food

Directly or indirectly dependent on plants.

2. Nutritional and Physical Features

2.1. Nutrition

Holozoic mode: ingestion of food.

2.2. Digestion

Internal cavity for digestion.

2.3. Food Reserves

Stored as glycogen or fat.

2.4. Growth Pattern

Definite growth leading to a specific shape and size.

3. Sensory and Motor Mechanisms

3.1. Higher Forms

Exhibit elaborate sensory and neuromotor systems.

3.2. Locomotion

Most are capable of movement.

4. Reproduction

4.1. Mode of Reproduction

Sexual reproduction through copulation.

4.2. Embryological Development

Post-fertilization development stages.

Viruses, Viroids, Prions and Lichens

Viruses

1.1. Nature

Non-cellular, considered at the edge of living and non-living.

1.2. Structure

Inert crystalline structure outside living cells.
Contain RNA or DNA (not both), encapsulated in a protein coat (capsid).

1.3. Replication

Obligate parasites; replicate using the host's machinery.

1.4. Discovery and Research

Identified by Dmitri Ivanowsky (1892) and further studied by M.W. Beijerinek and W.M. Stanley.

1.5. Diseases

Cause various diseases like mumps, smallpox, herpes, influenza, and AIDS.

Viroids

1. Discovery and Nature

1.1. Discovery

Discovered in 1971 by T.O. Diener.

1.2. Disease Caused

Responsible for potato spindle tuber disease.

2. Characteristics

2.1. Size and Composition

Smaller than viruses.

2.2. Structure

Consists of free RNA without a protein coat.

2.3. Molecular Weight

RNA of low molecular weight.

Prions

1. Nature and Transmission

1.1. Composition

Infectious agents are made of abnormally folded proteins.

1.2. Size

Similar in size to viruses.

2. Diseases Caused by Prions

2.1. Bovine Spongiform Encephalopathy (BSE)

Also known as mad cow disease, affects cattle.

2.2. Variant Creutzfeldt–Jakob Disease (CJD)

Analogous disease in humans.

Lichens

1. Nature of Lichens

1.1. Symbiotic Relationship

Mutual association between algae and fungi.

1.2. Components

Algal part (phycobiont) and fungal part (mycobiont).

2. Roles of Components

2.1. Phycobiont (Algae)

Autotrophic; prepares food for the fungus.

2.2. Mycobiont (Fungi)

Heterotrophic; provides shelter, and absorbs water and mineral nutrients.

3. Characteristics and Identification

3.1. Appearance

Appear as a single organism in nature.

3.2. Pollution Indicators

Do not grow in polluted areas, indicating good air quality.

Summary

1. Historical Classification

1.1. Aristotle's Classification

Based on simple morphological characters.

1.2. Linnaeus' Two Kingdoms

Divided organisms into Plantae and Animalia.

2. Whittaker's Five Kingdom Classification

2.1. Kingdoms Proposed

Monera, Protista, Fungi, Plantae, Animalia.

2.2. Criteria Used

Cell structure, body organization, nutrition mode, reproduction, phylogenetic relationships.

3. Kingdom Monera

3.1. Characteristics

Includes bacteria, showing extensive metabolic diversity.

3.2. Nutrition Modes

Autotrophic or heterotrophic.

4. Kingdom Protista

4.1. Composition

Single-celled eukaryotes (e.g., Chrysophytes, Euglenoids).

4.2. Cellular Structure

Defined nucleus and membrane-bound organelles.

4.3. Reproduction

Asexual and sexual methods.

5. Kingdom Fungi

5.1. Diversity

Diverse in structure and habitat.

5.2. Nutrition

Mostly saprophytic.

5.3. Reproduction

Asexual and sexual types.

5.4. Classes

Phycomycetes, Ascomycetes, Basidiomycetes, Deuteromycetes.

6. Kingdom Plantae

6.1. Composition

Eukaryotic, chlorophyll-containing organisms (algae, bryophytes, etc.).

6.2. Life Cycle

Alternation of generations (gametophytic, sporophytic).

7. Kingdom Animalia

7.1. Characteristics

Heterotrophic eukaryotes, multicellular, no cell walls.

7.2. Nutrition

Holozoic.

7.3. Reproduction

Mostly sexual.

8. Acellular Organisms and Lichens

8.1. Excluded Groups

Viruses, viroids, and lichens not included in the five kingdoms.

8.2. Nature

Viruses and viroids: Acellular; Lichens: Symbiotic association.

Chapter 3 - Plant Kingdom

Introduction

1. Whittaker's Five Kingdom Classification

1.1. Overview

The classification includes Monera, Protista, Fungi, Animalia, and Plantae.

1.2. Focus

Detailed study of Kingdom Plantae in this chapter.

2. Evolution of Plant Kingdom Understanding

2.1. Changes Over Time

Exclusion of Fungi, Monera, and Protista (with cell walls) from Plantae.

2.2. Example

Cyanobacteria, formerly classified as algae, are no longer in Plantae.

2.3. Current Inclusions

Algae, Bryophytes, Pteridophytes, Gymnosperms, Angiosperms under Plantae.

3. Classification Systems for Angiosperms

3.1. Early Systems

Based on superficial morphological characters (e.g., Linnaeus' system).

3.2. Issues with Early Systems

Artificial and based on limited characters, emphasizing vegetative traits.

4. Natural Classification Systems

4.1. Basis

Consider external and internal features (ultrastructure, anatomy, embryology, phytochemistry).

4.2. Example

Classification by George Bentham and Joseph Dalton Hooker.

5. Modern Phylogenetic Systems

5.1. Approach

Based on evolutionary relationships and common ancestors.

5.2. Use of Diverse Information

Incorporates data from various sources, especially where fossil evidence is lacking.

6. Contemporary Methods in Taxonomy

6.1. Numerical Taxonomy

Uses all observable characteristics; employs computers for data processing.

6.2. Cytotaxonomy

Based on cytological information (chromosome number, structure).

6.3. Chemotaxonomy

Utilizes chemical constituents of plants for classification.

Algae

1. General Characteristics of Algae

1.1. Nature

Chlorophyll-bearing, simple, thalloid, autotrophic.

1.2. Habitat

Largely aquatic (freshwater and marine), also in moist stones, soils, and wood.

1.3. Associations

Found in symbiosis with fungi (lichen) and animals.

2. Form and Size

2.1. Variability

Range from colonial (e.g., Volvox) to filamentous forms (e.g., Ulothrix, Spirogyra).

2.2. Large Marine Forms

Some, like kelps, form massive plant bodies.

3. Reproduction in Algae

3.1. Vegetative Reproduction

Fragmentation, leading to new thalli.

3.2. Asexual Reproduction

Commonly through zoospores (flagellated, motile).

3.3. Sexual Reproduction

Isogamous (similar gametes), anisogamous (dissimilar gametes), or oogamous (large non-motile female and smaller motile male gamete).

4. Utility of Algae

4.1. Carbon Dioxide Fixation and Oxygen Production

Significant contributors to photosynthesis.

4.2. Primary Producers in Aquatic Food Cycles

Basis of food cycles for aquatic animals.

4.3. Algal Products

Food sources (Porphyra, Laminaria), hydrocolloids (algin, carrageen), and agar (Gelidium, Gracilaria).

4.4. Nutritional Supplements

Chlorella is used as a protein-rich food supplement.

5. Classification of Algae

5.1. Main Classes

Chlorophyceae, Phaeophyceae, Rhodophyceae.

Chlorophyceae

1. General Characteristics

1.1. Common Name

Known as green algae.

1.2. Plant Body

Can be unicellular, colonial, or filamentous.

1.3. Pigmentation

Grass green due to chlorophyll a and b.

2. Chloroplasts and Storage

2.1. Chloroplast Types

Vary in shape: discoid, plate-like, reticulate, cup-shaped, spiral, or ribbon-shaped.

2.2. Pyrenoids

Storage bodies in chloroplasts, containing protein and starch.

2.3. Food Storage

Some store food as oil droplets.

3. Cell Wall Composition

3.1. Structure

Rigid wall with an inner cellulose layer and an outer pectose layer.

4. Reproduction

4.1. Vegetative Reproduction

By fragmentation or various spore types.

4.2. Asexual Reproduction

Through flagellated zoospores in zoosporangia.

4.3. Sexual Reproduction

Types: isogamous, anisogamous, oogamous.

5. Common Examples

5.1. Notable Species

Chlamydomonas, Volvox, Ulothrix, Spirogyra, Chara.

Phaeophyceae

1. Habitat and Physical Characteristics

1.1. Habitat

Primarily found in marine environments.

1.2. Size and Form

Vary from simple filamentous forms (Ectocarpus) to large kelps.

1.3. Pigmentation

Contains chlorophyll a, c, carotenoids, and xanthophylls (fucoxanthin).

2. Color and Food Storage

2.1. Color Variation

Color ranges from olive green to brown, based on fucoxanthin content.

2.2. Food Storage

Stored as complex carbohydrates (laminarin, mannitol).

3. Cellular Structure

3.1. Cell Wall

Cellulosic wall with gelatinous algin coating.

3.2. Protoplast Composition

Contains plastids, a central vacuole, and nucleus.

4. Plant Body Structure

4.1. Components

Consists of holdfast (for attachment), stipe (stalk), and frond (leaf-like photosynthetic organ).

5. Reproduction

5.1. Vegetative Reproduction

Occurs by fragmentation.

5.2. Asexual Reproduction

Involves biflagellate zoospores (pear-shaped, two unequal flagella).

5.3. Sexual Reproduction

Can be isogamous, anisogamous, or oogamous.
Gametes are pyriform and have two laterally attached flagella.

6. Common Examples

6.1. Notable Species

Ectocarpus, Dictyota, Laminaria, Sargassum, Fucus.

Rhodophyceae

1. General Characteristics

1.1. Common Name

Known as red algae due to the red pigment r-phycoerythrin.

1.2. Habitat

Mostly marine, prevalent in warmer areas.

2. Adaptation and Structure

2.1. Light Adaptation

Thrive in well-lighted surface regions and at great ocean depths.

2.2. Thallus Structure

Red thalli are usually multicellular, some with complex organization.

3. Food Storage

3.1. Storage Substance

Floridian starch, similar to amylopectin and glycogen.

4. Reproductive Methods

4.1. Vegetative Reproduction

Occurs through fragmentation.

4.2. Asexual Reproduction

By non-motile spores.

4.3. Sexual Reproduction

Oogamous with non-motile gametes and complex post-fertilization developments.

5. Common Examples

5.1. Notable Species

Polysiphonia, Porphyra, Gracilaria, Gelidium.

Table

Bryophytes

1. General Characteristics

1.1. Common Types

Includes mosses and liverworts.

1.2. Habitat

Common in moist, shaded areas, especially in hills.

1.3. Nickname

Known as the 'amphibians of the plant kingdom' due to their dependency on water for sexual reproduction.

2. Plant Body and Habitat Adaptation

2.1. Differentiation

More differentiated than algae, but lacks true roots, stems, or leaves.

2.2. Structure

Thallus-like, prostrate or erect, attached by rhizoids.

2.3. Role in Ecology

Important in plant succession on bare rocks/soil.

3. Reproductive Features

3.1. Gametophyte Dominance

The main plant body is haploid and gametophyte.

3.2. Sex Organs

Multicellular antheridium (male) and archegonium (female).

3.3. Fertilization Process

Biflagellate antherozoids fertilize the egg in the archegonium.

4. Sporophyte Development

4.1. Zygote and Sporophyte Formation

Zygote forms sporophyte, dependent on the gametophyte for nourishment.

4.2. Spore Formation

Sporophyte cells undergo meiosis to produce haploid spores.

5. Economic and Ecological Importance

5.1. Limited Economic Use

Some mosses are used as food for animals, peat for fuel, and packing.

5.2. Ecological Significance

Pioneer in colonizing rocks, soil formation, and preventing soil erosion.

6. Classification

6.1. Subgroups

Divided into liverworts and mosses.

Liverworts

1. Habitat and Growth

1.1. Preferred Habitats

Common in moist, shady areas like stream banks, marshy ground, and deep woods.

1.2. Plant Body

Thalloid structure, as seen in Marchantia.

2. Thallus Structure

2.1. Nature

Dorsiventral, closely appressed to the substrate.

2.2. Leafy Liverworts

Possess tiny leaf-like appendages on stem-like structures.

3. Asexual Reproduction

3.1. Methods

By fragmentation or through gemmae (multicellular asexual buds).

3.2. Gemmae Formation

Form in gemma cups on the thallus and develop into new individuals.

4. Sexual Reproduction

4.1. Sex Organ Formation

Male and female organs produced on the same or different thalli.

4.2. Sporophyte Structure

Differentiated into foot, seta, and capsule.

4.3. Spore Formation

Spores produced post-meiosis in the capsule, leading to free-living gametophytes.

Mosses

1. Life Cycle and Gametophyte Stages

1.1. Dominant Stage

Gametophyte is the predominant life cycle stage.

1.2. Protonema Stage

The first stage, develops from a spore; creeping, green, branched, filamentous.

1.3. Leafy Stage

Develops from secondary protonema; has upright axes with spirally arranged leaves.

2. Structure and Attachment

2.1. Axes and Leaves

Slender axes bearing leaves.

2.2. Rhizoids

Multicellular, branched structures for soil attachment.

3. Vegetative Reproduction

3.1. Methods

Occurs by fragmentation and budding in secondary protonema.

4. Sexual Reproduction

4.1. Sex Organs

Antheridia (male) and archegonia (female) are produced on leafy shoots.

4.2. Fertilization to Sporophyte

Zygote develops into sporophyte (foot, seta, capsule).

4.3. Spore Formation

The capsule contains spores formed post-meiosis.

4.4. Spore Dispersal

Mosses have an elaborate spore dispersal mechanism.

5. Common Examples

5.1. Notable Moss Species

Funaria, Polytrichum, Sphagnum.

Pteridophytes

1. General Characteristics and Uses

1.1. Composition

Include horsetails and ferns.

1.2. Uses

Medicinal purposes, soil-binding, ornamental plants.

1.3. Evolutionary Significance

First terrestrial plants with vascular tissues (xylem and phloem).

2. Habitat and Growth Conditions

2.1. Preferred Habitats

Thrive in cool, damp, shady places; some in sandy soil.

3. Dominant Life Cycle Phase

3.1. Sporophyte

Main plant body is a sporophyte with differentiated root, stem, and leaves.

3.2. Vascular Tissues

Possess well-differentiated vascular tissues.

4. Structure of Sporophytes

4.1. Leaf Types

Microphylls (small leaves) or macrophylls (large leaves).

4.2. Sporangia and Sporophylls

Sporangia borne on leaf-like appendages called sporophylls.

4.3. Strobili or Cones

Compact structures formed by sporophylls in some species.

5. Reproduction

5.1. Spore Production

Sporangia produce spores by meiosis.

5.2. Gametophyte Development

Spores germinate to form small, multicellular, photosynthetic gametophytes (prothallus).

6. Sexual Reproduction and Gametophytes

6.1. Gametophyte Structure

Require cool, damp, shady places for growth.

6.2. Sex Organs

Antheridia (male) and archegonia (female).

6.3. Fertilization

Involves transfer of antherozoids to archegonium; formation of zygote.

7. Homosporous and Heterosporous Pteridophytes

7.1. Homosporous

Produce one kind of spore.

7.2. Heterosporous

Produce two kinds of spores (megaspores and microspores).

8. Classification

8.1. Classes

Psilopsida (Psilotum), Lycopsida (Selaginella, Lycopodium), Sphenopsida (Equisetum), Pteropsida (Dryopteris, Pteris, Adiantum).

Gymnosperms

1. General Characteristics

1.1. Definition

'Gymnosperms': plants with naked seeds (no ovary wall).

1.2. Plant Types

Include medium-sized to tall trees and shrubs.

1.3. Notable Examples

Giant redwood tree Sequoia, Cycas, Pinus, Cedrus.

2. Root and Stem Structure

2.1. Roots

Generally tap roots; some have mycorrhizal associations (Pinus) or coralloid roots (Cycas).

2.2. Stems

Unbranched (Cycas) or branched (Pinus, Cedrus).

3. Leaf Adaptations

3.1. Types

Simple or compound, with adaptations for extreme conditions.

3.2. Leaf Structure

Needle-like leaves in conifers to reduce surface area and water loss.

4. Reproduction

4.1. Heterosporous Nature

Produce microspores and megaspores.

4.2. Sporophylls and Strobili

Sporophylls arranged in strobili or cones.

4.3. Microsporangiate (Male)

Produce pollen grains (male gametophytes) in microsporangia.

4.4. Megasporangiate (Female)

Bear ovules on megasporophylls; female gametophytes develop in megasporangia.

5. Pollination and Fertilization

5.1. Pollen Grain Development

Pollen grains develop and are released from microsporangia.

5.2. Fertilization Process

Pollen grains reach ovules; pollen tube grows towards archegonia.

5.3. Zygote and Seed Development

Fertilization leads to zygote, which develops into an embryo; ovules develop into seeds.

6. Gametophyte Independence

6.1. Dependency

Male and female gametophytes do not have a free-living existence; remain within sporangia.

7. Classification

7.1. Major Classes

Psilopsida, Lycopsida, Sphenopsida, Pteropsida.

Angiosperms

1. Distinctive Features

1.1. Definition

Known as flowering plants, with ovules enclosed in fruits.

1.2. Contrast with Gymnosperms

Ovules and pollen grains develop in flowers, unlike the naked ovules of gymnosperms.

2. Diversity and Habitat

2.1. Size Range

Vary from smallest Wolffia to tall Eucalyptus trees (over 100 meters).

2.2. Habitat Variability

Found in a wide range of habitats.

3. Economic and Practical Importance

3.1. Human Benefits

Source of food, fodder, fuel, medicines, and other commercial products.

4. Classification of Angiosperms

4.1. Primary Classes

Divided into dicotyledons and monocotyledons.

Summary

1. Algae

1.1. Characteristics

Chlorophyll-bearing, simple, thalloid, autotrophic, largely aquatic.

1.2. Classification

Divided into Chlorophyceae, Phaeophyceae, and Rhodophyceae based on pigments and stored food.

1.3. Reproduction

Vegetative (fragmentation), asexual (spores), sexual (isogamy, anisogamy, oogamy).

2. Bryophytes

2.1. Habitat and Dependency

Live in the soil but need water for sexual reproduction.

2.2. Plant Body

Differentiated thallus-like body, attached by rhizoids.

2.3. Classification

Liverworts and mosses.

2.4. Reproductive Organs

Antheridia (male), archegonia (female).

2.5. Sporophyte Formation

The zygote produces haploid spores.

3. Pteridophytes

3.1. Plant Body

Sporophyte with differentiated root, stem, and leaves.

3.2. Vascular Tissues

Well-differentiated.

3.3. Reproduction

Sporangia produce spores; need cool, damp places for gametophyte growth.

4. Gymnosperms

4.1. Ovule Nature

Ovules not enclosed by ovary wall (naked seeds).

4.2. Reproductive Structures

Microsporangia and megasporangia on sporophylls forming cones.

4.3. Fertilization and Seed Formation

Pollen grains, pollen tubes, and fertilization in ovules lead to embryo and seed formation.

5. Angiosperms

5.1. Key Feature

Seeds enclosed in fruits.

5.2. Size Range

Range from smallest Wolffia to tall trees like Eucalyptus.

5.3. Classification

Divided into dicotyledons and monocotyledons.

Chapter 4 - Animal Kingdom

Introduction

1. Diversity in Animal Kingdom

1.1. Observation

Animals exhibit diverse structures and forms.

1.2. Species Count

Over a million animal species have been described.

2. Need for Classification

2.1. Organizational Necessity

Classification is essential to systematically organize this vast diversity.

2.2. Systematic Positioning

Helps in assigning systematic positions to newly described species.

Basis of Classification

1. Fundamental Features in Animals

1.1. Structural and Form Differences

Despite varying structures and forms, certain fundamental features are common.

2. Criteria Used in Classification

2.1. Cell Arrangement

How cells are organized in an animal's body.

2.2. Body Symmetry

Symmetrical arrangement of body parts (e.g., radial, bilateral).

2.3. Coelom Nature

Presence or type of body cavity (coelom).

2.4. Digestive System Patterns

Variations in the structure and function of the digestive system.

2.5. Circulatory System

Type and complexity of the circulatory system.

2.6. Reproductive System

Reproductive structures and methods.

Levels of Organization

1. Variations in Cellular Organisation

1.1. Cellular Level

Exhibited by sponges; cells arranged as loose aggregates.

1.2. Tissue Level

In coelenterates; cells performing similar functions form tissues.

2. Organ and Organ System Levels

2.1. Organ Level

Seen in Platyhelminthes and higher phyla; tissues form specific organs.

2.2. Organ System Level

Higher complexity in Annelids, Arthropods, Molluscs, Echinoderms, Chordates; organs form functional systems.

3. Complexity in Organ Systems

3.1. Digestive System

Varies from incomplete (single opening) in Platyhelminthes to complete (two openings: mouth and anus).

3.2. Circulatory System Types

Open type: Blood directly bathes cells and tissues.
Closed type: Blood circulates through a series of vessels.

Symmetry

1. Basis of Categorization

1.1. Importance

Symmetry is a key aspect in categorizing animals.

2. Types of Symmetry

2.1. Asymmetrical

Sponges mostly show asymmetry (no plane divides them into equal halves).

2.2. Radial Symmetry

Body divided into identical halves by any plane passing through the central axis.
Exhibited by coelenterates, ctenophores, and echinoderms.

2.3. Bilateral Symmetry

Body divided into identical left and right halves in only one plane.
Seen in annelids, arthropods, and others.

Diploblastic and Triploblastic Organization

1. Diploblastic Animals

1.1. Definition

Animals with two embryonic layers: ectoderm (external) and endoderm (internal).

1.2. Examples

Coelenterates.

1.3. Intermediate Layer

Presence of an undifferentiated layer, mesoglea, between ectoderm and endoderm.

2. Triploblastic Animals

2.1. Definition

Animals with a third germinal layer, mesoderm, between ectoderm and endoderm.

2.2. Coverage

Includes animals from Platyhelminthes to Chordates.

Coelom

1. Importance in Classification

1.1. Role

The presence or absence of a body cavity is a key classification criterion.

2. Types of Body Cavities

2.1. Coelomates

Animals with a body cavity (coelom) lined by mesoderm.
Examples: Annelids, molluscs, arthropods, echinoderms, hemichordates, chordates.

2.2. Pseudocoelomates

Body cavity (pseudocoelom) not lined by mesoderm; mesoderm present in scattered pouches.
Examples: Aschelminthes.

2.3. Acoelomates

Animals lacking a body cavity.
Examples: Platyhelminthes.

Segmentation

1. Concept of Segmentation

1.1. Definition

Body division into segments with serial repetition of some organs.

2. Metameric Segmentation

2.1. Example

Earthworm demonstrates metameric segmentation.

2.2. Phenomenon

Known as metamerism.

Notochord

1. Definition of Notochord

1.1. Nature

A mesodermally derived, rod-like structure formed during embryonic development.

2. Significance in Classification

2.1. Chordates

Animals with a notochord are termed chordates.

2.2. Non-chordates

Animals without a notochord, e.g., Porifera to Echinoderms, are called non-chordates.

Classification of Animals

1. Basis of Classification

1.1. Fundamental Features

Classification based on common fundamental features as discussed previously.

2. Phyla in Animal Kingdom

2.1. Overview

Different phyla are classified based on these fundamental characteristics.

2.2. Characteristic Features

Important features of each phylum are described for classification purposes.

Phylum – Porifera

1. General Characteristics

1.1. Common Name

Known as sponges.

1.2. Habitat

Mostly marine and mostly asymmetrical.

1.3. Level of Organisation

Primitive multicellular with the cellular level of organization.

2. Water Transport System

2.1. Canal System

Water enters through the ostia, into the spongocoel, and exits through the osculum.

2.2. Function

Assists in food gathering, respiratory exchange, and waste removal.

3. Cellular Structure

3.1. Choanocytes

Collar cells lining spongocoel and canals.

3.2. Digestion

Intracellular digestion.

4. Body Support

4.1. Skeleton

Composed of spicules or spongin fibers.

5. Reproduction

5.1. Hermaphroditism

Both eggs and sperm are produced by the same individual.

5.2. Asexual Reproduction

Occurs by fragmentation.

5.3. Sexual Reproduction

Involves gamete formation, internal fertilization, and indirect development with a distinct larval stage.

6. Examples

6.1. Notable Species

Sycon (Scypha), Spongilla (Freshwater sponge), Euspongia (Bath sponge).

Phylum – Coelenterata (Cnidaria)

1. General Characteristics

1.1. Habitat

Aquatic, mostly marine, either sessile or free-swimming.

1.2. Symmetry

Radially symmetrical.

1.3. Cnidoblasts

Presence of cnidoblasts or cnidocytes with stinging capsules (nematocysts).

2. Organisation and Body Structure

2.1. Level of Organisation

Exhibit tissue level of organization; diploblastic.

2.2. Gastro-Vascular Cavity

Central cavity with a single opening (mouth on hypostome).

2.3. Digestion

Both extracellular and intracellular.

3. Skeleton in Some Cnidarians

3.1. Composition

Skeleton made of calcium carbonate (in corals).

4. Body Forms

4.1. Polyp and Medusa

Polyp: Sessile, cylindrical (e.g., Hydra, Adamsia).
Medusa: Umbrella-shaped, free-swimming (e.g., Aurelia).

5. Reproduction and Life Cycle

5.1. Alternation of Generation (Metagenesis)

Polyps produce medusae asexually; medusae form polyps sexually (e.g., Obelia).

6. Examples

6.1. Notable Species

Physalia (Portuguese man-of-war), Adamsia (Sea anemone), Pennatula (Sea-pen), Gorgonia (Sea-fan), Meandrina (Brain coral).

Phylum – Ctenophora

1. General Characteristics

1.1. Common Names

Known as sea walnuts or comb jellies.

1.2. Habitat

Exclusively marine.

1.3. Symmetry and Organisation

Radially symmetrical, diploblastic with tissue level of organisation.

2. Distinctive Features

2.1. Comb Plates

Body bears eight external rows of ciliated comb plates for locomotion.

2.2. Digestion

Both extracellular and intracellular.

2.3. Bioluminescence

Notable ability to emit light.

3. Reproduction

3.1. Sexes

Hermaphroditic (sexes are not separate).

3.2. Reproductive Mode

Only sexual reproduction.

3.3. Fertilisation and Development

External fertilisation with indirect development.

4. Examples

4.1. Notable Species

Pleurobrachia and Ctenoplana.

Phylum – Platyhelminthes

1. General Characteristics

1.1. Common Name

Known as flatworms due to their dorso-ventrally flattened bodies.

1.2. Habitat

Mostly endoparasites in animals, including humans.

2. Body Structure and Symmetry

2.1. Symmetry

Bilaterally symmetrical.

2.2. Organisation

Triploblastic, acoelomate animals with organ level of organization.

3. Parasitic Adaptations

3.1. Attachment Organs

Hooks and suckers in parasitic species.

3.2. Nutrient Absorption

Absorb nutrients directly through the body's surface.

4. Osmoregulation and Excretion

4.1. Flame Cells

Specialized cells for osmoregulation and excretion.

5. Reproduction

5.1. Hermaphroditic

Sexes are not separate.

5.2. Fertilisation and Development

Internal fertilization; development involves multiple larval stages.

5.3. Regeneration

High regeneration capacity in some species like Planaria.

6. Examples

6.1. Notable Species

Taenia (Tapeworm), Fasciola (Liver fluke).

Phylum – Aschelminthes

1. General Characteristics

1.1. Common Name

Known as roundworms due to their circular cross-section.

1.2. Habitats

Can be free-living, aquatic, terrestrial, or parasitic in plants and animals.

2. Body Organisation and Symmetry

2.1. Level of Organisation

Organ-system level of body organisation.

2.2. Symmetry

Bilaterally symmetrical.

2.3. Body Cavity

Triploblastic and pseudocoelomate.

3. Anatomical Features

3.1. Alimentary Canal

Complete with a well-developed muscular pharynx.

3.2. Excretion

Excretory tube leading to an excretory pore.

4. Reproduction

4.1. Dioecious

Separate sexes; often females are longer than males.

4.2. Fertilisation

Internal fertilisation.

4.3. Development

Can be direct (young resemble adults) or indirect.

5. Examples

5.1. Notable Species

Ascaris (Roundworm), Wuchereria (Filaria worm), Ancylostoma (Hookworm).

Phylum – Annelida

1. Habitat and Lifestyle

1.1. Habitats

Aquatic (marine and freshwater) or terrestrial.

1.2. Lifestyle

Free-living and sometimes parasitic.

2. Organisational and Symmetrical Features

2.1. Body Organisation

Organ-system level of body organisation.

2.2. Symmetry

Bilaterally symmetrical.

2.3. Body Cavity

Triploblastic, metamerically segmented, coelomate.

3. Body Structure

3.1. Segmentation

Body surface divided into segments or metameres.

3.2. Musculature

Longitudinal and circular muscles aid in locomotion.

4. Specialised Features

4.1. Parapodia

Lateral appendages in aquatic annelids (e.g., Nereis) for swimming.

4.2. Circulatory System

Closed type circulatory system.

4.3. Excretory System

Nephridia for osmoregulation and excretion.

5. Neural and Reproductive Systems

5.1. Neural System

Consists of paired ganglia connected to a double ventral nerve cord.

5.2. Reproduction

Sexual; Nereis is dioecious, while earthworms and leeches are monoecious.

6. Examples

6.1. Notable Species

Nereis, Pheretima (Earthworm), Hirudinaria (Blood-sucking leech).

Phylum – Arthropoda

1. Phylum Overview

1.1. Size and Diversity

Largest phylum in Animalia, including insects; over two-thirds of all named species.

1.2. Organisation Level

Organ-system level of organization.

2. Physical Characteristics

2.1. Symmetry and Body Plan

Bilaterally symmetrical, triploblastic, segmented, coelomate.

2.2. Exoskeleton

Body covered by a chitinous exoskeleton.

2.3. Body Division

Consists of head, thorax, and abdomen.

2.4. Appendages

Jointed appendages (arthros: joint; poda: appendages).

3. Respiratory and Circulatory Systems

3.1. Respiratory Organs

Gills, book gills, book lungs, or tracheal system.

3.2. Circulatory System

Open type.

4. Sensory and Excretory Organs

4.1. Sensory Organs

Antennae, compound and simple eyes, statocysts.

4.2. Excretory System

Malpighian tubules.

5. Reproduction and Development

5.1. Sexes

Mostly dioecious.

5.2. Fertilisation

Usually internal.

5.3. Reproductive Nature

Mostly oviparous.

5.4. Development

Direct or indirect.

6. Examples and Significance

6.1. Economically Important

Apis (Honey bee), Bombyx (Silkworm), Laccifer (Lac insect).

6.2. Vectors

Anopheles, Culex, Aedes (Mosquitoes).

6.3. Gregarious Pest

Locusta (Locust).

6.4. Living Fossil

Limulus (King crab).

Phylum – Mollusca

1. Phylum Overview

1.1. Size of Phylum

Second largest animal phylum.

1.2. Habitat

Terrestrial or aquatic (marine or freshwater).

2. Body Organisation and Features

2.1. Organisation Level

Organ-system level of organization.

2.2. Symmetry and Body Plan

Bilaterally symmetrical, triploblastic, coelomate.

2.3. Body Structure

Unsegmented with a calcareous shell, a distinct head, muscular foot, and visceral hump.

2.4. Mantle

A mantle covering the visceral hump; forms the mantle cavity.

3. Respiratory and Excretory Systems

3.1. Mantle Cavity and Gills

Mantle cavity housing feather-like gills for respiration and excretion.

4. Sensory and Feeding Organs

4.1. Sensory Tentacles

Located in the anterior head region.

4.2. Radula

A file-like rasping organ for feeding.

5. Reproduction

5.1. Sexes

Usually dioecious.

5.2. Reproductive Nature

Oviparous with indirect development.

6. Examples

6.1. Notable Species

Pila (Apple snail), Pinctada (Pearl oyster), Sepia (Cuttlefish), Loligo (Squid), Octopus (Devilfish), Aplysia (Sea hare), Dentalium (Tusk shell), Chaetopleura (Chiton).

Phylum – Echinodermata

1. General Characteristics

1.1. Name Origin

Named for their spiny bodies (Echinodermata means "spiny-bodied").

1.2. Habitat

Exclusively marine.

1.3. Organisation Level

Organ-system level of organisation.

2. Symmetry and Body Plan

2.1. Adult Symmetry

Radially symmetrical.

2.2. Larval Symmetry

Bilaterally symmetrical.

2.3. Body Cavity

Triploblastic and coelomate.

3. Distinctive Features

3.1. Endoskeleton

Made of calcareous ossicles.

3.2. Water Vascular System

Unique to echinoderms; aids in locomotion, feeding, and respiration.

4. Digestive and Excretory Systems

4.1. Digestive System

Complete, with mouth on ventral side and anus on dorsal side.

4.2. Excretory System

Absent.

5. Reproduction

5.1. Sexes

Separate.

5.2. Reproductive Mode

Sexual reproduction; usually external fertilisation.

5.3. Development

Indirect with free-swimming larva.

6. Examples

6.1. Notable Species

Asterias (Starfish), Echinus (Sea urchin), Antedon (Sea lily), Cucumaria (Sea cucumber), Ophiura (Brittle star).

Phylum – Hemichordata

1. Classification Status

1.1. Earlier Classification

Previously considered under Phylum Chordata as a sub-phylum.

1.2. Current Status

Now recognized as a separate phylum under non-chordata.

2. General Characteristics

2.1. Rudimentary Structure

Presence of a rudimentary structure, stomochord, similar to notochord in the collar region.

2.2. Habitat

Worm-like marine animals.

3. Body Organisation and Plan

3.1. Level of Organisation

Organ-system level of organization.

3.2. Symmetry and Body Plan

Bilaterally symmetrical, triploblastic, coelomate.

3.3. Body Parts

The body is divided into an anterior proboscis, a collar, and a long trunk.

4. Systems and Functions

4.1. Circulatory System

Open type.

4.2. Respiratory System

Respiration through gills.

4.3. Excretory System

The proboscis gland as the excretory organ.

5. Reproduction

5.1. Sexes

Separate.

5.2. Fertilisation

External.

5.3. Development

Indirect.

6. Examples

6.1. Notable Species

Balanoglossus, Saccoglossus.

Phylum – Chordata

1. Fundamental Characteristics

1.1. Defining Features

Presence of a notochord, dorsal hollow nerve cord, and paired pharyngeal gill slits.

1.2. Body Plan and Systems

Bilaterally symmetrical, triploblastic, coelomate with the organ-system level of organization.

1.3. Additional Features

Post-anal tail and closed circulatory system.

2. Subphyla of Chordata

2.1. Urochordata or Tunicata

Notochord is present only in the larval tail; examples include Ascidia, Salpa, and Doliolum.

2.2. Cephalochordata

Notochord extends from head to tail, persistent throughout life; for example: Branchiostoma (Amphioxus or Lancelet).

2.3. Vertebrata

Notochord is replaced by vertebral column in adults; vertebrates possess additional features like a muscular heart and kidneys.

3. Distinctive Features of Vertebrates

3.1. Vertebral Column

Notochord is replaced by a cartilaginous or bony vertebral column in adults.

3.2. Heart and Kidneys

Ventral muscular heart with varying chambers; kidneys for excretion and osmoregulation.

3.3. Appendages

Paired appendages, either fins or limbs.

4. Chordates vs Vertebrates

4.1. Key Difference

All vertebrates are chordates, but not all chordates are vertebrates.

Class – Cyclostomata

1. General Characteristics

1.1. Lifestyle

Ectoparasites on some fishes.

1.2. Body Structure

Elongated body with 6-15 pairs of gill slits for respiration.

1.3. Mouth Structure

Sucking and circular mouth without jaws.

2. Physical Features

2.1. Body Surface

Devoid of scales and paired fins.

2.2. Skeletal Structure

Cranium and vertebral column are cartilaginous.

3. Circulatory System

3.1. Type

Closed circulatory system.

4. Reproductive Behavior

4.1. Spawning Migration

Marine but migrate to freshwater for spawning.

4.2. Lifecycle

Die after spawning; larvae metamorphose and return to the ocean.

5. Examples

5.1. Notable Species

Petromyzon (Lamprey), Myxine (Hagfish).

Class – Chondrichthyes

1. General Characteristics

1.1. Habitat

Marine animals with streamlined bodies.

1.2. Skeletal Structure

Cartilaginous endoskeleton.

1.3. Mouth Location

Ventral position.

2. Distinctive Features

2.1. Notochord

Persistent throughout life.

2.2. Gills

Separate gill slits without operculum.

2.3. Skin and Teeth

Tough skin with minute placoid scales; teeth are modified placoid scales.

3. Physical and Biological Traits

3.1. Predatory Nature

Powerful jaws; generally predaceous.

3.2. Swimming Requirement

Constant swimming due to absence of air bladder.

3.3. Heart Structure

Two-chambered (one auricle and one ventricle).

4. Special Adaptations

4.1. Electric Organs

Some species like Torpedo have electric organs.

4.2. Poison Sting

Some species like Trygon possess a poison sting.

5. Thermal Regulation and Reproduction

5.1. Thermal Regulation

Poikilothermous (cold-blooded).

5.2. Reproductive System

Separate sexes; internal fertilisation; males have claspers on pelvic fins.

5.3. Development

Many species are viviparous.

6. Examples

6.1. Notable Species

Scoliodon (Dogfish), Pristis (Sawfish), Carcharodon (Great white shark), Trygon (Stingray).

Class – Osteichthyes

1. Habitat and Structure

1.1. Habitat

Includes both marine and freshwater fishes.

1.2. Endoskeleton

Bony endoskeleton.

1.3. Body Shape

Streamlined body; mouth mostly terminal.

2. Gills and Skin

2.1. Gills

Four pairs of gills, covered by an operculum on each side.

2.2. Skin

Covered with cycloid/ctenoid scales.

3. Buoyancy and Circulation

3.1. Air Bladder

Regulates buoyancy.

3.2. Heart

Two-chambered (one auricle and one ventricle).

4. Thermal Regulation and Reproduction

4.1. Thermal Nature

Cold-blooded animals.

4.2. Sexes

Separate.

4.3. Fertilisation

Usually external.

4.4. Reproductive Nature

Mostly oviparous; development is direct.

5. Examples

5.1. Marine Species

Exocoetus (Flying fish), Hippocampus (Sea horse).

5.2. Freshwater Species

Labeo (Rohu), Catla (Katla), Clarias (Magur).

5.3. Aquarium Fishes

Betta (Fighting fish), Pterophyllum (Angel fish).

Class – Amphibia

1. Habitat and Adaptation

1.1. Dual Habitat

Can live in both aquatic and terrestrial habitats.

1.2. Limbs

Most have two pairs of limbs.

2. Body Features

2.1. Body Division

Divisible into head and trunk; tail present in some.

2.2. Skin

Moist skin without scales.

2.3. Sensory Organs

Eyes with eyelids; a tympanum as the ear.

3. Physiological Systems

3.1. Digestive and Excretory Systems

Alimentary, urinary, and reproductive tracts open into the cloaca.

3.2. Respiratory System

Respiration through gills, lungs, and skin.

3.3. Circulatory System

Three-chambered heart (two auricles and one ventricle).

4. Reproduction and Development

4.1. Thermal Nature

Cold-blooded (poikilothermic).

4.2. Reproductive System

Separate sexes; external fertilisation.

4.3. Development

Oviparous with indirect development.

5. Examples

5.1. Notable Species

Bufo (Toad), Rana (Frog), Hyla (Tree frog), Salamandra (Salamander), Ichthyophis (Limbless amphibian).

Class – Reptilia

1. Movement and Habitat

1.1. Locomotion

Named for their creeping or crawling mode of locomotion.

1.2. Habitat

Mostly terrestrial.

2. Body Features

2.1. Skin

Dry, cornified skin with epidermal scales or scutes.

2.2. Ears

Lack external ear openings; tympanum represents the ear.

2.3. Limbs

Two pairs of limbs, when present.

3. Physiological Traits

3.1. Circulatory System

Three-chambered heart, but four-chambered in crocodiles.

3.2. Thermal Regulation

Poikilothermic (ability to vary body temperature).

4. Reproduction and Development

4.1. Skin Shedding

Snakes and lizards shed scales as skin cast.

4.2. Reproductive System

Separate sexes; internal fertilisation.

4.3. Development

Oviparous with direct development.

5. Examples

5.1. Non-Poisonous

Chelone (Turtle), Testudo (Tortoise), Chameleon (Tree lizard), Calotes (Garden lizard), Crocodilus (Crocodile), Alligator (Alligator), Hemidactylus (Wall lizard).

5.2. Poisonous Snakes

Naja (Cobra), Bangarus (Krait), Vipera (Viper).

Class – Aves

1. Distinctive Features

1.1. Feathers

Presence of feathers; capable of flight (except flightless birds like the Ostrich).

1.2. Beak

Possession of a beak.

2. Limbs and Locomotion

2.1. Forelimbs

Modified into wings.

2.2. Hind Limbs

Scaled, modified for walking, swimming, or clasping tree branches.

3. Skin and Skeletal Structure

3.1. Skin

Dry skin; oil gland present at the tail's base.

3.2. Endoskeleton

Fully ossified and pneumatic (hollow bones).

4. Digestive and Circulatory Systems

4.1. Digestive Tract

Additional chambers like the crop and gizzard.

4.2. Heart

Completely four-chambered.

5. Thermoregulation and Respiration

5.1. Thermal Regulation

Warm-blooded (homoiothermous).

5.2. Respiratory System

Lungs, supplemented by air sacs.

6. Reproduction and Development

6.1. Sexes

Separate.

6.2. Fertilisation

Internal.

6.3. Reproductive Nature

Oviparous; direct development.

7. Examples

7.1. Notable Species

Corvus (Crow), Columba (Pigeon), Psittacula (Parrot), Struthio (Ostrich), Pavo (Peacock), Aptenodytes (Penguin), Neophron (Vulture).

Class – Mammalia

1. Habitat and Diversity

1.1. Habitats

Found in various habitats: polar ice caps, deserts, mountains, forests, grasslands, and caves.

1.2. Adaptations

Adapted to fly or live in water.

2. Distinctive Features

2.1. Mammary Glands

Presence of milk-producing mammary glands for nourishing young ones.

2.2. Limbs

Two pairs, adapted for various activities: walking, running, climbing, burrowing, swimming, and flying.

3. Physical Characteristics

3.1. Skin and Hair

Skin with the unique presence of hair.

3.2. External Ears

Presence of external ears or pinnae.

3.3. Dentition

Different types of teeth are present in the jaw.

4. Physiological Systems

4.1. Circulatory System

Four-chambered heart.

4.2. Thermoregulation

Homoiothermous (constant body temperature).

4.3. Respiratory System

Respiration by lungs.

5. Reproduction and Development

5.1. Reproductive System

Separate sexes; internal fertilization.

5.2. Nature

Mostly viviparous with few exceptions.

5.3. Development

Direct development.

6. Examples

6.1. Oviparous

Ornithorhynchus (Platypus).

6.2. Viviparous

Macropus (Kangaroo), Pteropus (Flying fox), Camelus (Camel), Macaca (Monkey), Rattus (Rat), Canis (Dog), Felis (Cat), Elephas (Elephant), Equus (Horse), Delphinus (Common dolphin), Balaenoptera (Blue whale), Panthera tigris (Tiger), Panthera leo (Lion).

Table

Flowchart

Table

Flowchart

Summary

1. Fundamental Features for Classification

Level of organization, symmetry, cell organization, coelom, segmentation, and notochord.

2. Distinctive Features of Each Phylum/Class

2.1. Porifera

The multicellular, cellular level of organization, flagellated choanocytes.

2.2. Coelenterata

Aquatic, tentacles with cnidoblasts, mostly sessile/free-floating.

2.3. Ctenophora

Marine with comb plates.

2.4. Platyhelminthes

Flat body, bilateral symmetry, parasites with suckers/hooks.

2.5. Aschelminthes

Pseudocoelomates, parasitic/non-parasitic roundworms.

2.6. Annelida

Metameric segmentation, true coelom.

2.7. Arthropoda

Abundant, jointed appendages.

2.8. Mollusca

Soft body, external calcareous shell.

2.9. Echinodermata

Spiny skin, water vascular system.

2.10. Hemichordata

Worm-like marine, body with proboscis, collar, and trunk.

3. Phylum Chordata

3.1. General Features

Notochord, dorsal hollow nerve cord, pharyngeal gill slits.

3.2. Subdivision

Agnatha (Cyclostomata), Gnathostomata (Pisces, Tetrapoda).

4. Classes Under Chordata

4.1. Cyclostomata

Primitive, ectoparasites on fishes.

4.2. Chondrichthyes

Cartilaginous fishes, marine.

4.3. Osteichthyes

Bony fishes.

4.4. Amphibia

Dual habitat, both land and water.

4.5. Reptilia

Dry, cornified skin, some limbless.

4.6. Aves

Warm-blooded, feathers, wings.

4.7. Mammalia

Mammary glands, hairs on the skin, mostly viviparous.

Section 2 - Structural Organization in Plants and Animals

Chapter 5 - Morphology of Flowering Plants

Introduction

Overview

Fascination with the diversity in the structure of higher plants.

Common characteristics: presence of roots, stems, leaves, flowers, and fruits.

Classification of Plants (Refer to Chapters 2 and 3)

Based on morphological and other characteristics.

Importance of standard technical terms and definitions.

Understanding the variations in different parts as adaptations.

Adaptations of Plants

Adaptations to various habitats.

For purposes such as protection, climbing, storage, etc.

Root System and Shoot System

Root System: The underground part of the flowering plant.

Shoot System: The portion above the ground.

Examples

Observation: Pulling out a weed reveals roots, stems, and leaves.

Potential presence of flowers and fruits.

The Root

Types of Root Systems

Dicotyledonous Plants:

Formation of primary root from radicle.
Development of lateral roots (secondary, tertiary, etc.).
Constitutes the tap root system (e.g., mustard plant).

Monocotyledonous Plants:

Short-lived primary root.
Replacement by numerous roots from the stem base.
Constitutes the fibrous root system (e.g., wheat plant).

Adventitious Roots

Found in plants like grass, Monstera, and the banyan tree.

Arise from plant parts other than the radicle.

Main Functions of the Root System

Absorption: Water and minerals from the soil.

Anchorage: Providing stability to plant parts.

Storage: Reserve food material.

Synthesis: Plant growth regulators.

Regions of the Root

Root Cap

A thimble-like structure covering the root apex.

Protects the tender apex as the root grows through the soil.

Region of Meristematic Activity

Located a few millimeters above the root cap.

Characteristics:

Small cells.
Thin-walled.
Dense protoplasm.

Function: Cells divide repeatedly for root growth.

Region of Elongation

Situated proximal to the meristematic region.

Cells undergo rapid elongation and enlargement.

Responsible for the root's length growth.

Region of Maturation

Adjacent to the region of elongation.

Cells from this zone differentiate and mature.

Root hairs formation:

Epidermal cells develop into root hairs.
Function: Absorption of water and minerals from the soil.

The Stem

Identification of a Stem

Ascending part of the plant axis.

Develops from the plumule of a germinating seed.

Distinguished by the presence of branches, leaves, flowers, and fruits.

Structure of the Stem

Nodes and Internodes:

Nodes: Points where leaves are attached.
Internodes: Portions between two nodes.

Buds:

May be terminal (at the tip) or axillary (in the leaf axils).

Appearance:

Generally green when young.
Becomes woody and dark brown with age.

Functions of the Stem

Spreading out branches that bear leaves, flowers, and fruits.

Conducting water, minerals, and photosynthates.

Storage of food.

Support and protection.

Vegetative propagation.

The Leaf

Basic Description of a Leaf

A lateral, generally flattened structure on the stem.

Develops at the node with a bud in its axil.

Originates from shoot apical meristems arranged acropetally.

Primary organ for photosynthesis.

Parts of a Leaf

Leaf Base:

Attaches the leaf to the stem.
May bear stipules (small leaf-like structures).
In monocotyledons, expands into a sheath covering the stem.
In some leguminous plants, it becomes swollen (pulvinus).

Petiole:

Connects the leaf base to the lamina.
Flexible petioles allow leaf blades to flutter, aiding in cooling and air circulation.

Lamina (Leaf Blade):

Green, expanded part of the leaf.
Contains veins and veinlets.
Features a prominent middle vein (midrib).
Veins provide rigidity and transport channels for water, minerals, and food.

Variations in Leaves

Diverse shapes, margins, apex, surface, and extent of incision.

Variations adapt leaves to different environments and functions.

Venation

Definition of Venation

The arrangement of veins and veinlets in the lamina of a leaf.

Types of Venation

Reticulate Venation:

Veinlets form a network.
Common in dicotyledonous plants.

Parallel Venation:

Veins run parallel to each other within the lamina.
Characteristic of most monocotyledons.

Types of Leaves

Simple Leaves

Lamina is entire or incised without reaching the midrib.

Example: A leaf with incisions not touching the midrib.

Compound Leaves

Lamina incisions reach up to the midrib, dividing it into leaflets.

Bud present in the axil of the petiole but not in the axil of leaflets.

Two types:

Pinnately Compound Leaves:

Leaflets arranged on a common axis (rachis).
Rachis represents the midrib of the leaf.
Example: Neem.

Palmately Compound Leaves:

Leaflets attached at a common point at the tip of the petiole.
Example: Silk cotton.

Phyllotaxy

Definition of Phyllotaxy

The pattern of arrangement of leaves on the stem or branch.

Types of Phyllotaxy

Alternate Phyllotaxy:

A single leaf arises at each node in an alternate manner.
Examples: China rose, mustard, and sunflower plants.

Opposite Phyllotaxy:

A pair of leaves arise at each node, lying opposite to each other.
Examples: Calotropis and guava plants.

Whorled Phyllotaxy:

More than two leaves arise at a node forming a whorl.
Example: Alstonia.

The Inflorescence

Definition of Inflorescence

The arrangement of flowers on the floral axis.
Occurs when the shoot apical meristem changes to floral meristem.

Characteristics of Inflorescence

Internodes do not elongate, and the axis gets condensed.
Floral appendages appear laterally at successive nodes instead of leaves.
Solitary flowers result from the transformation of a shoot tip into a flower.

Types of Inflorescences

Racemose Inflorescence:

Main axis continues to grow.
Flowers are borne laterally in an acropetal succession (from base to apex).

Cymose Inflorescence:

Main axis terminates in a flower, limiting growth.
Flowers are borne in a basipetal order (from apex to base).

The Flower

1. Basic Concept ◦ A flower is the reproductive unit in angiosperms, meant for sexual reproduction. 2. Structure of a Flower ◦ Arrangement: Four whorls on the thalamus or receptacle. ◦ Whorls: ▪ Calyx: Outermost whorl, protective in function. ▪ Corolla: Next whorl, often colorful and attracts pollinators. ▪ Androecium: Male reproductive part, consists of stamens. ▪ Gynoecium: The female reproductive part, consists of carpels. ◦ Variations: ▪ Perianth: When calyx and corolla are not distinct. ▪ Bisexuality: Presence of both androecium and gynoecium. ▪ Unisexuality: Presence of either stamens or carpels only. 3. Symmetry of Flowers ◦ Actinomorphic: Radial symmetry, can be divided into two equal halves in any radial plane (e.g., mustard, datura, chilli). ◦ Zygomorphic: Bilateral symmetry, can be divided into two similar halves only in one vertical plane (e.g., pea, gulmohur, bean). ◦ Asymmetric: Irregular, cannot be divided into two similar halves by any plane (e.g., canna). 4. Floral Appendages ◦ Arranged in multiples of 3 (trimerous), 4 (tetramerous), or 5 (pentamerous). 5. Bracts ◦ Bracteate: Flowers with a reduced leaf at the base of the pedicel. ◦ Ebracteate: Flowers without bracts. 6. Positioning Based on Ovary ◦ Hypogynous: Gynoecium highest, ovary superior (e.g., mustard, china rose). ◦ Perigynous: Gynoecium central, ovary half inferior (e.g., plum, rose). ◦ Epigynous: Ovary enclosed by thalamus, ovary inferior (e.g., guava, cucumber).

Parts of a Flower

Calyx

Basic Definition

The calyx is the outermost whorl of the flower.

Sepals

Members of the calyx are known as sepals.

Characteristics:

Typically green and leaf-like.
Function: Protect the flower in the bud stage.

Types of Calyx

Gamosepalous:

Sepals are united.

Polysepalous:

Sepals are free (not fused).

Corolla

Corolla

Composed of petals.

Function: Usually brightly colored to attract insects for pollination.

Types:

Gamopetalous: Petals are united.
Polypetalous: Petals are free (not fused).

Variations: Shape and color vary greatly, including tubular, bell-shaped, funnel-shaped, or wheel-shaped.

Aestivation

Definition: The arrangement of sepals or petals in a floral bud in relation to other members of the same whorl.

Main Types:

Valvate: Sepals or petals just touch each other at the margins without overlapping (e.g., Calotropis).
Twisted: Each appendage overlaps the next one (e.g., china rose, lady’s finger, cotton).
Imbricate: Margins of sepals or petals overlap without a specific direction (e.g., Cassia, gulmohur).
Vexillary (Papilionaceous): A specific pattern in pea and bean flowers with five petals, where the largest (standard) overlaps the lateral petals (wings), which in turn overlap the two smallest anterior petals (keel).

Androecium

Basic Structure of Androecium

Composed of stamens, representing the male reproductive organ.

Each stamen consists of:

Filament: A stalk.
Anther: Usually bilobed, containing two chambers called pollen-sacs.

Pollen-Sacs: Produce pollen grains.

Staminode: A sterile stamen.

Attachment and Union of Stamens

Epipetalous: Stamens attached to petals, as in brinjal.

Epiphyllous: Stamens attached to the perianth, as in lilies.

Stamen Arrangement:

Polyandrous: Stamens remain free.
Monoadelphous: Stamens united into one bunch (e.g., china rose).
Diadelphous: Stamens united into two bundles (e.g., pea).
Polyadelphous: Stamens united into more than two bundles (e.g., citrus).

Variations in Stamens

Variation in the length of filaments within a flower (e.g., Salvia, mustard).

Gynoecium

Gynoecium: Female Reproductive Part

Composed of one or more carpels.
Parts of a Carpel:

Stigma: Receptive surface for pollen grains, typically at the style's tip.
Style: Elongated tube connecting the ovary to the stigma.
Ovary: Enlarged basal part, bearing one or more ovules.

Carpel Arrangement

Apocarpous: Carpels are free (e.g., lotus, rose).
Syncarpous: Carpels are fused (e.g., mustard, tomato).
Post-fertilization: Ovules develop into seeds and ovary into fruit.

Placentation: Arrangement of Ovules

Marginal: Placenta forms a ridge along ovary's ventral suture, ovules in two rows (e.g., pea).
Axile: Placenta is axial with ovules attached in a multilocular ovary (e.g., china rose, tomato).
Parietal: Ovules on inner wall or periphery of ovary; ovary becomes two-chambered with a false septum (e.g., mustard).
Free Central: Ovules borne on a central axis, no septa (e.g., Dianthus).
Basal: Single ovule attached at the ovary base (e.g., sunflower).

The Fruit

Basic Definition

A fruit is a mature or ripened ovary, developed after fertilization in flowering plants.

Parthenocarpic Fruit: Fruit formed without fertilization of the ovary.

Structure of a Fruit

Pericarp: Wall of the fruit, can be dry or fleshy.

Pericarp Layers:

Epicarp: Outer layer.
Mesocarp: Middle layer, often fleshy.
Endocarp: Inner layer.

Types of Fruits

Drupe:

Develops from monocarpellary superior ovaries.
Usually one-seeded.
Example: Mango and Coconut.

Mango: Thin epicarp, fleshy edible mesocarp, stony hard endocarp.
Coconut: Fibrous mesocarp.

The Seed

Formation of Seeds

Seeds develop from fertilized ovules.

Components of a Seed

Seed Coat: Outer protective layer.
Embryo: Comprises:

Radicle: The embryonic root.
Embryonal Axis: Connects the radicle and cotyledons.
Cotyledons: Seed leaves, vary in number:

One cotyledon (Monocotyledons): e.g., wheat, maize.
Two cotyledons (Dicotyledons): e.g., gram, pea.

Structure of a Dicotyledonous Seed

Structure of Monocotyledonous Seed

Endospermic Nature

Monocotyledonous seeds are generally endospermic, with some exceptions like orchids.

Seed Coat and Fruit Wall

In cereals (e.g., maize), the seed coat is membranous and often fused with the fruit wall.

Endosperm

Bulky and stores food.

Enclosed by a proteinous layer, the aleurone layer, separates it from the embryo.

Embryo

Small, located in a groove at one end of the endosperm.

Components:

Scutellum: A large, shield-shaped cotyledon.
Embryonal Axis: Short, with a plumule and a radicle.

Protective Sheaths:

Coleoptile: Encloses the plumule.
Coleorhiza: Encloses the radicle.

Semi-Technical Description of a Typical Flowering Plants

Description Sequence

Begin with the plant's habit and follow with vegetative and floral characters.

Order: Roots → Stem → Leaves → Inflorescence → Flower Parts.

Floral Diagram and Floral Formula

Floral Diagram:

Shows the number and arrangement of flower parts and their relation to each other.
Mother axis position indicated by a dot at the top of the diagram.
Sequence in whorls: Calyx (outermost), Corolla, Androecium, Gynoecium (centre).

Floral Formula:

Uses symbols to represent different parts of the flower:

Br for bracteate.
K for calyx.
C for corolla.
P for perianth.
A for androecium.
G for gynoecium (upper G for superior ovary, lower G for inferior ovary).
Symbols for male (⚤), female (♀), bisexual (♂♀), actinomorphic (⊕), zygomorphic (⊝).

Fusion is indicated by brackets; adhesion by a line above symbols.
Demonstrates cohesion and adhesion within and between whorls.

Example: Mustard Plant

Represented in the given floral diagram and formula.

Family: Brassicaceae.

Solanaceae

Vegetative Characters

Plant Types:

Mostly herbs and shrubs.
Rarely small trees.

Stem

Stem Characteristics:

Herbaceous, occasionally woody.

Aerial, erect, cylindrical.

Branched, can be solid or hollow.

Surface: Hairy or glabrous.

Notable Example: Underground stem in potato (Solanum tuberosum).

Leaves

Leaf Characteristics

Arrangement: Alternate placement on the stem.

Type: Mostly simple leaves, rarely pinnately compound.

Stipules: Exstipulate (lacking stipules).

Venation: Reticulate pattern.

Floral Characters

Inflorescence

Types: Solitary, axillary, or cymose (as in Solanum species).

Flower

Nature: Bisexual, actinomorphic (radially symmetrical).

Calyx

Structure: Composed of five united sepals.
Persistence: Persistent in nature.
Aestivation: Valvate (sepals just touch each other at the margins).

Corolla

Structure: Made of five united petals.
Aestivation: Valvate.

Androecium

Stamens: Five in number, epipetalous (attached to petals).

Gynoecium

Structure: Bicarpellary (two carpels), syncarpous (carpels fused together).
Ovary: Superior, bilocular (two chambers).
Placenta: Swollen, with many ovules, axile placentation.

Fruits and Seeds

Fruit Types: Berry or capsule.
Seeds: Numerous, endospermous.

Economic Importance

Food Sources

Includes tomato, brinjal, and potato.

Spices

Example: Chilli.

Medicinal Plants

Examples: Belladonna, Ashwagandha.

Fumigatory Uses

Example: Tobacco.

Ornamental Plants

Example: Petunia

Summary

General Characteristics

Wide variation in shape, size, structure, nutrition, lifespan, habit, and habitat.
Well-developed root and shoot systems.

Root System

Types: Tap root (common in dicotyledonous plants) and fibrous root (in monocotyledonous plants).
Modifications: Storage, support, respiration.

Shoot System

Components: Stem, leaves, flowers, and fruits.
Stem: Distinguished by nodes, internodes, multicellular hair, positively phototropic.
Leaves: Lateral outgrowths from the stem, green for photosynthesis, variable in shape, size, margin, apex, and lamina incisions.

Flowers and Inflorescences

Flowers: Modified shoots for sexual reproduction.
Arrangement: Various types of inflorescences.
Features: Diversity in structure, symmetry, ovary position, petal and sepal arrangement, ovules.

Post-Fertilization Changes

Ovary transforms into fruit.
Ovules develop into seeds.

Seed Types

Monocotyledonous or dicotyledonous.
Variation in shape, size, and viability period.

Classification and Identification

Based on floral characteristics.
Described in a specific sequence using scientific terms.
Summarized in floral diagrams and floral formulae.

Chapter 6 - Anatomy of Flowering Plants

Introduction

Overview of Structural Similarities and Variations

Noticeable in both plants and animals, in external morphology.

Internal Structure and Functional Organization

Focus of the study in higher plants.

Similarities and differences are evident internally.

Anatomy of Plants

Study of the internal structure of plants.

Hierarchical organization:

Cells: Basic unit.
Tissues: Cells organized into tissues.
Organs: Tissues form organs.

Diversity in Organ Structure

Different organs exhibit distinct internal structures.

Angiosperm Anatomy

Monocots and dicots show anatomical differences.

Adaptations in internal structures to diverse environments.

The Tissue System

Concept of Tissue Systems

Tissues vary based on cell types, location in the plant body, structure, and function.

Types of Tissue Systems

Epidermal Tissue System:

Forms the outer protective covering.

Ground or Fundamental Tissue System:

Constitutes the bulk of the plant body, involved in various functions like photosynthesis, storage, and support.

Vascular or Conducting Tissue System:

Specialized for transport of water, minerals, and food throughout the plant.

Epidermal Tissue System

Overview

Forms the outermost covering of the plant body.
Comprises epidermal cells, stomata, trichomes, and hairs.

Epidermis Structure

Usually a single layer of elongated, compactly arranged cells.
Parenchymatous cells with minimal cytoplasm and a large vacuole.
Covered externally by a waxy layer called the cuticle, which prevents water loss (absent in roots).

Stomata

Present in the epidermis of leaves.
Function: Regulate transpiration and gaseous exchange.
Structure: Composed of two bean-shaped guard cells (dumb-bell shaped in grasses).
Guard cells are thicker towards the stomatal pore, contain chloroplasts, and control stomatal opening.

Subsidiary Cells

Specialized epidermal cells near guard cells, shaping the stomatal apparatus.

Hairs (Trichomes)

Root Hairs: Unicellular extensions of epidermal cells, aiding in water and mineral absorption.
Stem Hairs (Trichomes): Usually multicellular, may be branched/unbranched, soft/stiff, and sometimes secretory.
Function: Help in reducing water loss through transpiration.

The Ground Tissue System

Composition of Ground Tissue

Constitutes all tissues in the plant body except for the epidermis and vascular bundles.

Types of Simple Tissues

Includes parenchyma, collenchyma, and sclerenchyma.

Location and Function

Parenchyma:

Predominantly in the cortex, pericycle, pith, and medullary rays of primary stems and roots.
In leaves, it forms the mesophyll, containing chloroplasts for photosynthesis.

The Vascular Tissue System

Composition of Vascular System

Comprised of complex tissues: phloem and xylem.

Vascular Bundles

Phloem and xylem together form vascular bundles.

Types of Vascular Bundles

Open Vascular Bundles (Dicotyledons):

Contains cambium between phloem and xylem.
Can form secondary xylem and phloem.

Closed Vascular Bundles (Monocotyledons):

No cambium present.
Do not form secondary tissues.

Arrangement of Vascular Bundles

Radial Arrangement:

The xylem and phloem are alternately arranged along different radii, typical in roots.

Conjoint Arrangement:

The xylem and phloem are situated along the same radius, common in stems and leaves.
The phloem usually located on the outer side of the xylem.

Anatomy of Dicotyledonous and Monocotyledonous Plants

Objective

To understand tissue organization in roots, stems, and leaves of dicotyledonous and monocotyledonous plants.

Method of Study

Examination of transverse sections of mature zones of these organs is recommended for clarity.

Dicotyledonous Root

Epiblema (Outermost Layer)

Characterized by cells protruding as unicellular root hairs.

Cortex

Comprises several layers of thin-walled parenchyma cells with intercellular spaces.

Endodermis

Innermost cortex layer.
A single layer of barrel-shaped cells, no intercellular spaces.
Presence of Casparian strips (suberin) on tangential and radial walls.

Pericycle

Thick-walled parenchymatous cells.
Site for initiation of lateral roots and vascular cambium during secondary growth.

Pith

Small or inconspicuous in dicotyledonous roots.

Conjunctive Tissue

Parenchymatous cells are located between the xylem and phloem.

Vascular Bundles

Two to four xylem and phloem patches.
Cambium ring development occurs between the xylem and phloem.

Stele

Includes all tissues inside the endodermis (pericycle, vascular bundles, and pith).

Monocotyledonous Root

Similarities to Dicot Root

Contains epidermis, cortex, endodermis, pericycle, vascular bundles, and pith.

Distinct Features

Xylem Bundles: More than six (polyarch), in contrast to fewer in dicot roots.
Pith: Large and well-developed.

Lack of Secondary Growth

Monocotyledonous roots do not undergo secondary growth.

Dicotyledonous Stem

Epidermis

Outermost protective layer.
Covered with a cuticle, may have trichomes and stomata.

Cortex

Located between epidermis and pericycle.
Consists of three sub-zones:

Hypodermis: Outer layer with collenchymatous cells for mechanical strength.
Middle Layers: Rounded, thin-walled parenchymatous cells with intercellular spaces.
Endodermis: Innermost layer, rich in starch grains (starch sheath).

Pericycle

Inner side of endodermis, above phloem.
Composed of semi-lunar sclerenchymatous patches.

Medullary Rays

Radially placed parenchymatous cells between vascular bundles.

Vascular Bundles

Arranged in a ring, characteristic of dicot stems.
Each bundle is conjoint, open, with endarch protoxylem.

Pith

Central portion of the stem.
Composed of rounded, parenchymatous cells with large intercellular spaces.

Monocotyledonous Stem

Hypodermis

Composed of sclerenchymatous tissue for mechanical support.

Vascular Bundles

Numerous and scattered throughout the stem.

Each bundle is surrounded by a sclerenchymatous bundle sheath.

Conjoint and closed, with varying sizes (smaller on the periphery and larger in the center).

Ground Tissue

Large and conspicuous, composed of parenchyma.

Other Features

Absence of phloem parenchyma.

Presence of water-containing cavities within the vascular bundles.

Dorsiventral (Dicotyledonous) Leaf

Epidermis

Covers both upper (adaxial) and lower (abaxial) surfaces.

Has a prominent cuticle.

Abaxial epidermis typically has more stomata than adaxial epidermis.

Mesophyll

Tissue between upper and lower epidermis.

Contains chloroplasts for photosynthesis.

Made up of parenchyma cells.

Two cell types:

Palisade Parenchyma: Elongated cells arranged vertically and parallel, located adaxially.
Spongy Parenchyma: Oval or round, loosely arranged cells below palisade cells, with large spaces and air cavities.

Vascular System

Includes vascular bundles seen in veins and midrib.

Size of bundles varies with vein size.

Reticulate venation in dicot leaves.

Bundles surrounded by thick-walled bundle sheath cells.

Xylem positioning identifiable within the vascular bundle.

Isobilateral (Monocotyledonous) Leaf

Similarities to Dorsiventral Leaf

Shares many anatomical features with the dorsiventral leaf.

Distinctive Characteristics

Stomata: Present on both surfaces of the epidermis.
Mesophyll: Not differentiated into palisade and spongy parenchyma.

Bulliform Cells in Grasses

Adaxial epidermal cells modify into large, empty, colorless bulliform cells.
Function:

Turgid bulliform cells keep the leaf surface exposed.
Flaccid bulliform cells during water stress cause leaf curling, minimizing water loss.

Venation Pattern

Parallel venation leads to near similar sizes of vascular bundles (except in main veins).

Diagram - Stem

Diagram - Leaf

Summary

Tissue Classification

Meristematic Tissues:

Types: Apical, lateral, intercalary.

Permanent Tissues:

Types: Simple and complex.

Functions of Tissues

Assimilation and storage of food.
Transportation of water, minerals, and photosynthates.
Mechanical support.

Tissue Systems

Epidermal Tissue System:

Comprises epidermal cells, stomata, and epidermal appendages.

Ground Tissue System:

The main bulk of the plant is divided into cortex, pericycle, and pith.

Vascular Tissue System:

Formed by xylem and phloem.

Vascular Bundles

Types are based on the presence of cambium, and the location of the xylem and phloem.
Functions in the translocation of water, minerals, and food material.

Differences between Monocots and Dicots

Variations in the type, number, and location of vascular bundles.
Secondary growth is mostly in dicotyledonous roots and stems.

Chapter 7 - Structural Organization in Animals

Introduction

Cellular Functions in Unicellular Organisms

Single-cell perform all vital functions: digestion, respiration, and reproduction.

Multicellular Organisms

Complex bodies with specialized cells performing specific functions.
Examples: Hydra (simple) and humans (complex).

Tissue Organization

Groups of similar cells and intercellular substances perform specific functions.
Definition: Tissue.
Fundamental in complex animals, consisting of only four basic types of tissues.

Formation of Organs

Tissues are organized in specific proportions and patterns to form organs (e.g., stomach, lung, heart, kidney).

Organ Systems

Multiple organs performing a common function form organ systems (e.g., digestive system, respiratory system).
Exhibit division of labor, contributing to the survival of the organism as a whole.

Organ and Organ System

Tissue to Organ Formation

Basic tissues organize to form organs.

Each organ comprises one or more types of tissues.

Organ Systems

Organs associate to form organ systems for efficient and coordinated cellular activities.

Example: The human heart contains all four tissue types (epithelial, connective, muscular, neural).

Evolutionary Trend

Complexity in organs and organ systems follows a discernable evolutionary trend.

Detailed study in this area is part of advanced biology (Class XII curriculum).

Morphology and Anatomy

Morphology: Study of external form and features.

In animals, refers to external appearance of organs/body parts.

Anatomy: Study of internal structures, traditionally used in the context of animal biology.

Example for Study: Frog as a representative of vertebrates.

Frogs

Classification

Belong to class Amphibia of phylum Chordata.

Common species in India: Rana tigrina.

Body Temperature

Cold-blooded (poikilotherms): Body temperature varies with the environment.

Camouflage

Ability to change color to blend with surroundings.

Protects from predators (mimicry).

Seasonal Behavior

Not visible during peak summer and winter.

Summer Sleep: Aestivation to escape extreme heat.

Winter Sleep: Hibernation to survive cold conditions.

Morphology

Skin

Smooth and slippery due to mucus.

Moist condition maintained.

Color: Olive green with dark spots (dorsal side); pale yellow (ventral side).

Absorbs water through the skin.

Body Structure

Divided into head and trunk; neck and tail absent.

Nostrils located above the mouth.

Eyes with nictitating membrane for protection in water.

Tympanum (ear) on either side of eyes for sound reception.

Limbs

Forelimbs and hind limbs aid in swimming, walking, leaping, and burrowing.

Hind limbs: Larger, muscular, end in five digits, webbed for swimming.

Forelimbs: Smaller, end in four digits.

Sexual Dimorphism

Male frogs: Distinguished by vocal sacs and a copulatory pad on the first digit of forelimbs.

Female frogs: Lack these features.

Anatomy

Body Cavity and Organ Systems

Houses digestive, circulatory, respiratory, nervous, excretory, and reproductive systems.
Each system has well-developed structures and functions.

Digestive System

Consists of the alimentary canal and digestive glands.
Includes mouth, buccal cavity, esophagus, stomach, intestine, rectum, and cloaca.
The liver and pancreas function as digestive glands.

Respiratory System

Cutaneous respiration in water, pulmonary respiration on land.
Lungs are elongated, pink, sac-like structures for air respiration.
Skin acts as a respiratory organ in water.

Circulatory and Lymphatic Systems

The closed-type vascular system with a heart, blood vessels, and blood.
The lymphatic system includes lymph, lymph channels, and lymph nodes.
Heart with three chambers (two atria and one ventricle).

Excretory System

Consists of kidneys, ureters, cloaca, and urinary bladder.
Eliminates nitrogenous wastes, functioning as ureotelic.

Nervous System and Sense Organs

Central nervous system (brain and spinal cord), peripheral nervous system, autonomic nervous system.
Sense organs include the eyes, a tympanum (ear), and sensory papillae.

Reproductive System

Male frogs have testes; female frogs have ovaries.
External fertilization occurs in water.
Development involves a larval stage (tadpole) and metamorphosis.

Ecological Significance

Frogs control insect populations and maintain ecological balance.
In some cultures, frog legs are consumed as food.

Diagram

Diagram

Summary

Cellular Organization

Composed of cells, tissues, organs, and organ systems exhibiting division of labour for survival.

Tissue Structure

Group of cells with intercellular substances performing specific functions.
Epithelial tissues line body surfaces, cavities, ducts, and tubes.

Indian Bullfrog (Rana tigrina)

Common species in India.

Skin and Respiratory Function

Covered by skin with mucous glands.
Skin is vascularized, aiding in respiration in both water and land.

Body Division and Tongue

Body divided into head and trunk.
Possesses a muscular, bilobed tongue for prey capture.

Digestive System

Includes oesophagus, stomach, intestine, rectum, and cloaca.
Main digestive glands: liver and pancreas.

Respiratory Adaptations

Cutaneous respiration in water.
Pulmonary respiration on land.

Circulatory System

Closed system with single circulation.
Red blood cells are nucleated.

Nervous System

Divided into central, peripheral, and autonomic nervous systems.

Urinogenital System

Kidneys and urinogenital ducts leading to cloaca.
Separate male and female reproductive organs.
Male: Testes.
Female: Ovaries, laying 2500-3000 eggs at a time.

Reproduction and Development

External fertilization and development.
Eggs hatch into tadpoles, which undergo metamorphosis into adult frogs.

Section 3 - Cell: Structure and Functions

Chapter 8 - Cell: The Unit of Life

Introduction

Living vs Non-Living Things

Distinction is based on the presence or absence of the basic unit of life - the cell.

Cellular Composition of Organisms

All organisms are composed of cells.

Unicellular Organisms: Consist of a single cell (e.g., bacteria, amoeba).

Multicellular Organisms: Composed of many cells (e.g., humans, plants).

What is a Cell?

Cell as the Basic Unit of Life

Capable of independent existence.

Performs essential life functions.

Fundamental structural and functional unit of all living organisms.

Historical Discoveries

Anton Von Leeuwenhoek: First observation and description of a live cell.

Robert Brown: Discovery of the nucleus.

Advancements in Microscopy

Development of the microscope and its evolution to the electron microscope.

Microscopy advancements have revealed detailed cellular structures.

Cell Theory

Foundations of Cell Theory

Matthias Schleiden (1838): Observed plant cells forming tissues.
Theodore Schwann (1839): Studied animal cells, identified the plasma membrane and cell wall in plant cells.

Schleiden and Schwann's Contribution

Proposed that both animal and plant bodies are composed of cells and cell products.

Rudolf Virchow's Contribution (1855)

Proposed that new cells form from pre-existing cells (Omnis cellula-e cellula).
Modified Schleiden and Schwann’s hypothesis, giving cell theory its final shape.

Modern Understanding of Cell Theory

All living organisms are composed of cells and their products.
All cells arise from pre-existing cells.

An Overview of Cell

Basic Cell Structure

Plant cells (e.g., onion cell): Distinct cell wall and cell membrane.
Animal cells (e.g., human cheek cells): Outer membrane as the delimiting structure.

Nucleus and Chromosomes

Dense membrane-bound structure in cells.
Contains chromosomes with genetic material (DNA).

Cell Types

Eukaryotic Cells: Have membrane-bound nuclei.
Prokaryotic Cells: Lack a membrane-bound nucleus.

Cytoplasm

Semi-fluid matrix occupying cell volume.
Site of various cellular activities.

Cell Organelles

Eukaryotic Cells: Contain organelles like ER, Golgi complex, lysosomes, mitochondria, microbodies, and vacuoles.
Prokaryotic Cells: Lack these membrane-bound organelles.

Ribosomes

Found in both eukaryotic and prokaryotic cells.
Present in the cytoplasm, chloroplasts, mitochondria, and on rough ER.

Centrosome

Non-membrane bound organelle in animal cells, aiding in cell division.

Variations in Size and Shape

Sizes range from 0.3 µm (Mycoplasmas) to the large ostrich egg.
Shapes vary based on function: disc-like, polygonal, columnar, cuboid, threadlike, irregular.

Diagram

Prokaryotic Cells

Representation

Includes bacteria, blue-green algae, mycoplasma, and PPLO (Pleuro Pneumonia Like Organisms).

Size and Reproduction

Generally smaller and multiply faster than eukaryotic cells.

Shapes of Bacteria

Bacillus: Rod-like.
Coccus: Spherical.
Vibrio: Comma-shaped.
Spirillum: Spiral.

Cellular Organization

Surrounded by a cell wall (except mycoplasma).
Cytoplasm fills the cell.
No well-defined nucleus; genetic material is not enclosed by a nuclear membrane.

Genetic Material

Consists of genomic DNA (single chromosome/circular DNA).
Possession of additional small circular DNA known as plasmids, which confer unique characteristics like antibiotic resistance.

Cellular Components

Lack membrane-bound organelles, except for ribosomes.
Unique feature: Mesosomes (specialized infoldings of cell membrane).

Cell Envelope and its Modifications

Complex Cell Envelope

Consists of a three-layered structure: glycocalyx, cell wall, and plasma membrane.

Glycocalyx

Composition and thickness vary among bacteria.
Forms either a loose sheath (slime layer) or a thick, tough capsule.

Cell Wall

Provides shape and structural support.
Prevents the bacterium from bursting or collapsing.

Plasma Membrane

Selectively permeable.
Structurally similar to eukaryotic membranes.
Interacts with the external environment.

Mesosome

The membranous structure is formed by plasma membrane extensions.
Functions: Cell wall formation, DNA replication, distribution, respiration, secretion processes.

Chromatophores

Membranous extensions in cyanobacteria containing pigments.

Motility Structures

Flagella: For movement, with three parts (filament, hook, basal body).
Vary in number and arrangement.

Other Surface Structures

Pili: Elongated tubular structures, protein-made.
Fimbriae: Small, bristle-like fibers aiding in attachment to surfaces or host tissues.

Gram Staining Classification

Gram-Positive Bacteria: Take up Gram stain.
Gram-Negative Bacteria: Do not take up Gram stain.

Ribosomes and Inclusion Bodies

Ribosomes in Prokaryotes

Associated with the plasma membrane.

Size: Approximately 15 nm by 20 nm.

Composition: Two subunits (50S and 30S) forming 70S prokaryotic ribosomes.

Function: Sites of protein synthesis.

Polyribosomes/Polysomes: Chains of ribosomes attached to a single mRNA, translating it into proteins.

Inclusion Bodies

Store reserve material in the cytoplasm.

Not membrane-bound, lie free in the cytoplasm.

Types:

Phosphate Granules: For phosphate storage.
Cyanophycean Granules: In cyanobacteria.
Glycogen Granules: For glycogen storage.
Gas Vacuoles: Found in blue-green and certain photosynthetic bacteria.

Eukaryotic Cells

Eukaryotic Organisms

Include protists, plants, animals, and fungi.

Cellular Compartmentalization

Extensive compartmentalization of cytoplasm through membrane-bound organelles.

Nucleus and Chromosomes

Organized nucleus with a nuclear envelope.

Genetic material is organized into chromosomes.

Structural Complexities

Possess complex locomotory and cytoskeletal structures.

Differences Between Plant and Animal Cells

Plant Cells:

Have cell walls, plastids, and a large central vacuole.

Animal Cells:

Contain centrioles (absent in most plant cells).

Cell Membrane

Composition and Structure

Primarily composed of lipids and proteins.

Major lipids: Phospholipids arranged in a bilayer.

Lipid arrangement: Polar heads outward, hydrophobic tails inward.

Membrane also contains cholesterol.

Protein and Carbohydrate Content

Varies in different cells (e.g., human erythrocyte: 52% protein, 40% lipids).

Proteins classified as integral (embedded in the membrane) and peripheral (on the surface).

Fluid Mosaic Model (Singer and Nicolson, 1972)

Describes the cell membrane as a fluid structure with a "mosaic" of various proteins embedded in or attached to a bilayer of phospholipids.

Lateral movement of proteins within the bilayer is possible, contributing to membrane fluidity.

Functions of the Cell Membrane

Cell growth, intercellular junction formation, secretion, endocytosis, cell division.

Selectively permeable to molecules.

Transport Mechanisms

Passive Transport: Movement without energy use (e.g., diffusion, osmosis).

Active Transport: Energy-dependent movement against the concentration gradient (e.g., Na+/K+ Pump).

Cell Wall

Structure and Composition

A rigid, non-living layer forming the outer covering of plant and fungal cells.

Composition in algae: Cellulose, galactans, mannans, and minerals like calcium carbonate.

Composition in other plants: Cellulose, hemicellulose, pectins, and proteins.

Functions

Provides shape and structural integrity to the cell.

Protects against mechanical damage and infection.

Facilitates cell-to-cell interaction.

Acts as a barrier to undesirable macromolecules.

Types of Cell Walls

Primary Wall: Present in young plant cells, capable of growth.

Secondary Wall: Formed inside the primary wall in mature cells.

Middle Lamella

Layer of calcium pectate between cells.

Functions as a glue to hold neighboring cells together.

Cell Connectivity

Plasmodesmata: Channels traversing the cell wall and middle lamella, connecting the cytoplasm of adjacent cells.

Endomembrane System

Definition and Components

A group of membranous organelles with coordinated functions.

Includes endoplasmic reticulum (ER), Golgi complex, lysosomes, and vacuoles.

Exclusions from the Endomembrane System

Mitochondria, chloroplasts, and peroxisomes are not part of the endomembrane system due to their distinct and uncoordinated functions.

Endoplasmic Reticulum (ER)

Network of membranous tubules and cisternae.

Types: Rough ER (with ribosomes) and Smooth ER (without ribosomes).

Golgi Complex

Consists of stacks of flattened membranous sacs.

Involved in packaging and transporting substances.

Lysosomes

Membrane-bound vesicles containing digestive enzymes.

Involved in intracellular digestion and waste processing.

Vacuoles

Large, fluid-filled sacs.

Primarily involved in storage and maintaining cell turgidity.

The Endoplasmic Reticulum (ER)

Basic Structure

Network of tiny tubular structures in the cytoplasm, termed as the endoplasmic reticulum (ER).

Divides intracellular space into luminal (inside ER) and extra-luminal (cytoplasm) compartments.

Types of ER

Rough Endoplasmic Reticulum (RER):

Has ribosomes attached to its surface.
Involved in protein synthesis and secretion.
Extensive and continuous with the outer membrane of the nucleus.

Smooth Endoplasmic Reticulum (SER):

Lacks ribosomes on its surface, appearing smooth.
Major site for lipid synthesis.
In animal cells, involved in the synthesis of steroidal hormones.

Golgi apparatus

Discovery

First observed by Camillo Golgi in 1898.

Identified as densely stained reticular structures near the nucleus.

Structure

Composed of flat, disc-shaped sacs or cisternae, each 0.5µm to 1.0µm in diameter.

Cisternae are stacked parallel to each other, arranged concentrically near the nucleus.

Has two distinct faces: Convex cis (forming) face and concave trans (maturing) face.

Function

Performs packaging of materials for intracellular use or secretion outside the cell.

Vesicles from the ER fuse with the cis face and move towards the trans face.

Close association with the endoplasmic reticulum.

Involved in the modification of proteins synthesized in the ER.

Key site for the formation of glycoproteins and glycolipids.

Lysosomes

Formation

Membrane-bound vesicular structures formed by packaging in the Golgi apparatus.

Enzyme Composition

Rich in hydrolytic enzymes: lipases, proteases, carbohydrases.
Optimal activity in acidic conditions.
Capable of digesting carbohydrates, proteins, lipids, and nucleic acids.

Vacuoles

Structure and Location

Membrane-bound spaces in the cytoplasm.

Bound by a single membrane called tonoplast.

Contents

Contains water, sap, excretory products, and other substances not immediately useful for the cell.

Size in Plant Cells

Can occupy up to 90% of the cell volume in plant cells.

Function in Plant Cells

Tonoplast facilitates transport of ions and materials against concentration gradients into the vacuole.

Higher concentration of these substances in the vacuole compared to the cytoplasm.

Role in Different Organisms

In Amoeba: Contractile vacuole important for osmoregulation and excretion.

In protists: Food vacuoles formed by engulfing food particles.

Mitochondria

Visibility and Quantity

Not easily visible under the microscope without specific staining.

Number per cell varies based on the cell's physiological activity.

Shape and Size

Typically sausage-shaped or cylindrical.

Diameter: 0.2-1.0µm (average 0.5µm).

Length: 1.0-4.1µm.

Structure

Double membrane-bound organelle.

Outer membrane forms the boundary of the organelle.

Inner membrane has infoldings called cristae, increasing surface area.

Compartments

Outer compartment and inner compartment (matrix).

Matrix: Dense homogeneous substance.

Functions

Site of aerobic respiration.

Produces cellular energy in the form of ATP, hence known as the 'powerhouse' of the cell.

Genetic Material and Reproduction

Contains a single circular DNA molecule, RNA molecules, and 70S ribosomes.

Matrix includes components required for protein synthesis.

Mitochondria replicate by fission.

Plastids

Occurrence

Found in all plant cells and euglenoides.

Visibility

Large and easily observable under a microscope.

Types and Functions

Chloroplasts: Contain chlorophyll and carotenoid pigments for photosynthesis.
Chromoplasts: Contain fat-soluble pigments (carotene, xanthophylls) imparting yellow, orange, or red color.
Leucoplasts: Colorless, store nutrients.

Amyloplasts: Store carbohydrates.
Elaioplasts: Store oils and fats.
Aleuroplasts: Store proteins.

Chloroplast Structure

Shape: Lens-shaped, oval, spherical, discoid, or ribbon-like.
Size: Length 5-10µm, width 2-4µm.
Double membrane-bound with an inner membrane enclosing the stroma.

Internal Structure

Thylakoids: Flattened membranous sacs, arranged in stacks called grana.
Stroma Lamellae: Connect thylakoids of different grana.
Lumen: Enclosed by thylakoid membranes.
Stroma: Contains enzymes for carbohydrate and protein synthesis, DNA molecules, and ribosomes.
Chlorophyll pigments located in thylakoids.

Ribosomes in Chloroplasts

Smaller (70S) than cytoplasmic ribosomes (80S).

Ribosomes

Discovery

First observed as dense particles under an electron microscope by George Palade in 1953.

Composition

Composed of ribonucleic acid (RNA) and proteins.

Lacks a surrounding membrane.

Types

Eukaryotic Ribosomes: 80S type.

Prokaryotic Ribosomes: 70S type.

Subunits

Each ribosome has two subunits: a larger and a smaller one.

80S ribosomes consist of 60S and 40S subunits.

70S ribosomes consist of 50S and 30S subunits.

Svedberg Unit

'S' (Svedberg Unit) indicates sedimentation coefficient.

Reflects the density and size of the ribosomes.

Cytoskeleton

Composition and Structure

Composed of microtubules, microfilaments, and intermediate filaments.

These filamentous proteinaceous structures form a network in the cytoplasm.

Functions

Provides mechanical support to the cell.

Aids in cell motility.

Maintains the shape of the cell.

Diagram

Cilia and Flagella

Structure and Location

Hair-like outgrowths of the cell membrane.
Cilia are small, numerous, and oar-like.
Flagella are longer and fewer in number.

Function

Cilia: Movement of either the cell or the surrounding fluid.
Flagella: Responsible for the movement of the cell.

Prokaryotic vs Eukaryotic Flagella

Prokaryotic bacteria have flagella but structurally different from eukaryotic flagella.

Microscopic Structure

Covered with plasma membrane.
Core is called the axoneme, containing microtubules.

Axoneme Composition

Nine doublets of radially arranged peripheral microtubules.
A pair of centrally located microtubules.
Arrangement referred to as the 9+2 array.

Microtubule Connections

Central tubules connected by bridges.
Peripheral doublets connected by linkers.
Radial spokes connect peripheral doublets to central sheath.

Origin

Emerge from a centriole-like structure called basal bodies.

Centrosome and Centrioles

Centrosome Structure

Contains two cylindrical structures called centrioles.

Surrounded by pericentriolar materials.

Orientation and Composition of Centrioles

Centrioles are perpendicular to each other.

Each centriole has a cartwheel-like organization.

Composed of nine evenly spaced peripheral fibrils of tubulin protein.

Each peripheral fibril is a triplet, with adjacent triplets linked.

Central Hub

Proteinaceous central part called the hub.

Hub is connected to peripheral triplets by radial spokes made of protein.

Functions

Form the basal body of cilia or flagella.

Give rise to spindle fibers, forming the spindle apparatus during cell division in animal cells.

Nucleus

Discovery and Early Observations

First described by Robert Brown in 1831.
Chromatin is named by Flemming due to its staining by basic dyes.

Structure in Interphase

Contains chromatin (nucleoprotein fibers), nuclear matrix, and nucleoli.
Nuclear envelope with two parallel membranes and perinuclear space.
The outer membrane was continuous with an endoplasmic reticulum and bears ribosomes.

Nuclear Pores

Formed by the fusion of the two nuclear membranes.
Allow RNA and protein molecules to move between the nucleus and cytoplasm.

Variations in Nuclei

Typically one nucleus per cell, but variations exist.
Some cells (e.g., mammalian erythrocytes, sieve tube cells in plants) lack nuclei.

Nucleoplasm Components

Nucleoli: Spherical, non-membrane-bound, active in ribosomal RNA synthesis.
Chromatin: Loose, indistinct network of nucleoprotein fibers.

Chromosome Structure During Cell Division

Chromosomes become visible.
Contains DNA, histones, non-histone proteins, and RNA.

Centromere and Chromatids

Primary constriction on chromosomes.
Kinetochores on centromere sides.
Holds two chromatids together.

Types of Chromosomes Based on Centromere Position

Metacentric: Middle centromere, equal arms.
Sub-metacentric: Slightly off-center centromere, unequal arms.
Acrocentric: Near-end centromere, very short and long arms.
Telocentric: Terminal centromere.

Satellite

Secondary constrictions form a small fragment.

Diagram

Microbodies

Definition and Structure

Small, membrane-bound vesicles.

Present in both plant and animal cells.

Contents

Contain various enzymes.

Diagram

Summary

Cellular Variability

Cells vary in shape, size, and function.
Classification: Eukaryotic (with a nucleus) and Prokaryotic (without a nucleus).

Eukaryotic Cell Components

Consists of a cell membrane, nucleus, and cytoplasm.
Plant cells have an additional cell wall.

Plasma Membrane

Selectively permeable.
Facilitates transport of molecules.

Endomembrane System

Includes Endoplasmic Reticulum (ER), Golgi Complex, Lysosomes, and Vacuoles.
Each organelle performs specific functions.

Centrosome and Centrioles

Involved in locomotion (cilia and flagella) and cell division (spindle apparatus).

Nucleus

Contains nucleoli and chromatin.
Controls cellular activities and heredity.

Endoplasmic Reticulum (ER)

Rough ER (with ribosomes) and Smooth ER (without ribosomes).
Functions in substance transport, protein synthesis, and lipid metabolism.

Golgi Apparatus

Comprises flattened sacs for packing and transporting cellular secretions.

Lysosomes

Contain enzymes for macromolecule digestion.

Ribosomes

Involved in protein synthesis.
Found freely in the cytoplasm or associated with the ER.

Mitochondria

Site of oxidative phosphorylation and ATP generation.
Double membrane-bound with inner membrane forming cristae.

Plastids (Plant Cells)

Chloroplasts for photosynthesis.
Chromoplasts containing pigments like carotene and xanthophyll.

Nuclear Structure

Enclosed by a nuclear envelope with pores.
Contains nucleoplasm and chromatin material.

Chapter 9 - Biomolecules

Introduction

Elemental Analysis in Living Tissues

Analysis of plant, animal, or microbial tissues shows elements like carbon, hydrogen, oxygen, and others.

Comparison with Non-living Matter

Similar elemental analysis of earth's crust also reveals the presence of these elements.

Key Differences

No absolute differences in the types of elements present.

Relative abundance of carbon and hydrogen is higher in living organisms compared to earth's crust.

Significance

This difference indicates a unique chemical composition that distinguishes living matter from non-living.

How to Analyze Chemical Compositions?

Chemical Analysis of Living Tissues

Involves grinding tissue in trichloroacetic acid to obtain a slurry.
Results in two fractions: acid-soluble pool (filtrate) and acid-insoluble fraction (retentate).

Organic Compounds in Acid-Soluble Pool

Thousands of organic compounds are identified in living tissues.
Isolation and purification processes are used to separate specific compounds.
These compounds are collectively called ‘biomolecules’.

Inorganic Elements and Compounds

Determined by burning the tissue to leave an ‘ash’.
Ash contains inorganic elements (e.g., calcium, magnesium) and compounds (e.g., sulfate, phosphate).

Elemental Composition

Both living tissues and the earth's crust contain elements like hydrogen, oxygen, chlorine, and carbon.
Higher relative abundance of carbon and hydrogen in living organisms.

Classification of Biomolecules

From a chemical perspective: aldehydes, ketones, aromatic compounds, etc.
From a biological perspective: amino acids, nucleotide bases, fatty acids, etc.

Amino Acids

Organic compounds with an amino group and an acidic group.
Twenty types are found in proteins, each with a distinct R group.

Lipids

Water-insoluble, including simple fatty acids and glycerol.
Fatty acids can be saturated or unsaturated.
Glycerol can form monoglycerides, diglycerides, triglycerides.
Phospholipids (e.g., lecithin) are found in cell membranes.

Nucleotides and Nucleic Acids

Nucleosides (sugar + nitrogen base) and nucleotides (nucleoside + phosphate group).
Nucleic acids like DNA and RNA consist of nucleotides.

Formula

Structure

Table

Primary and Secondary Metabolites

Chemical Diversity in Organisms

Thousands of compounds isolated from living organisms.

Include both small and large biomolecules.

Primary Metabolites

Found in animal tissues.

Consist of essential biomolecules like amino acids, sugars, etc.

Play roles in normal physiological processes.

Secondary Metabolites

Commonly found in plants, fungi, and microbes.

Examples include alkaloids, flavonoids, rubber, essential oils, antibiotics, pigments, gums, spices.

Their functions in host organisms are not fully understood.

Importance of Secondary Metabolites

Many are beneficial for human welfare (e.g., in medicine, industry).

Some have ecological significance.

More information on their roles to be learned in advanced studies.

Table

Biomacromolecules

Acid-Soluble Pool Characteristics

Contains compounds with molecular weights ranging from 18 to around 800 daltons (Da).
Known as micromolecules or simple biomolecules.

Acid-Insoluble Fraction

Comprises mainly four types of organic compounds: proteins, nucleic acids, polysaccharides, and lipids.
Except for lipids, these have molecular weights above ten thousand daltons.
These are termed as macromolecules or biomacromolecules.

Lipids in Acid-Insoluble Fraction

Despite having lower molecular weights (not exceeding 800 Da), they are part of the insoluble fraction.
This is because lipids form structures like cell membranes which, when disrupted, become insoluble.
Lipids form vesicles upon cell disruption, leading to their categorization as macromolecules, albeit not strictly.

Polymeric Nature

Most biomacromolecules, except lipids, are polymers.
They represent the complex molecular composition of living tissues.

Overall Chemical Composition of Living Tissues

The acid soluble and insoluble fractions together represent the entire chemical composition of living organisms.
Water is the most abundant chemical in living organisms.

Proteins

Basic Structure

Proteins are polypeptides, composed of amino acids linked by peptide bonds.
Each protein is a polymer made up of 20 types of amino acids (e.g., alanine, cysteine, proline, tryptophan, lysine).

Heteropolymer Nature

Proteins are heteropolymers, not homopolymers, due to the diversity of amino acids.

Amino Acids Classification

Essential Amino Acids: Cannot be synthesized by the body; must be obtained through diet.
Non-Essential Amino Acids: Can be synthesized by the body.

Functions of Proteins

Diverse roles in organisms:

Transport nutrients across cell membranes.
Fight infectious organisms (immune response).
Act as hormones and enzymes.

Examples: Collagen (abundant in animals) and RuBisCO (abundant in the biosphere).

Nutritional Importance

Dietary proteins are a source of essential amino acids.
Essential for health and must be included in the diet.

Polysaccharides

Definition and Composition

Polysaccharides are long chains of sugars, composed of monosaccharides.
Examples include cellulose, starch, glycogen, and inulin.

Cellulose

A homopolymer consisting of glucose units.
Major component of plant cell walls.
Used in the production of paper and cotton fibers.

Starch and Glycogen

Starch: Plant energy storage polysaccharide, forms helical structures capable of trapping iodine (I2), resulting in a blue color.
Glycogen: Animal variant of starch, stored in liver and muscle tissues.

Inulin

A polymer of fructose, found in some plants.

Structure of Polysaccharides

Have a reducing end (right end) and a non-reducing end (left end).
Can form branched structures.
Starch forms helical secondary structures; cellulose does not.

Complex Polysaccharides

Include amino-sugars and chemically modified sugars (e.g., glucosamine, N-acetyl galactosamine).
Chitin is an example, forming the exoskeleton of arthropods.
These are mostly homopolymers.

Glycogen Structure

Nucleic Acids

Basic Composition

Nucleic acids are polynucleotides, forming a significant part of the macromolecular fraction in cells.
Composed of nucleotides, each consisting of a heterocyclic compound (nitrogenous base), a monosaccharide (sugar), and phosphate.

Nitrogenous Bases

There are five main bases:

Purines: Adenine (A) and Guanine (G).
Pyrimidines: Cytosine (C), Thymine (T), and Uracil (U).

Purines have a double-ring structure, while pyrimidines have a single-ring.

Sugar Component

Ribose in RNA (Ribonucleic Acid).
2’ Deoxyribose in DNA (Deoxyribonucleic Acid).

Types of Nucleic Acids

DNA: Contains deoxyribose sugar; responsible for storing and transferring genetic information.
RNA: Contains ribose sugar; plays a role in protein synthesis and other cellular processes.

Structural Features

Nucleotides in DNA and RNA are linked by phosphodiester bonds.
DNA typically forms a double helix structure, while RNA is usually single-stranded.

Structure of Proteins

Overview

Proteins are complex heteropolymers made up of amino acids.
Their structure is understood at four different levels: primary, secondary, tertiary, and quaternary.

Primary Structure

Refers to the linear sequence of amino acids in the protein.
The order in which amino acids are arranged dictates the protein's function.
Each protein begins with an N-terminal amino acid and ends with a C-terminal amino acid.

Secondary Structure

Involves the folding of the amino acid chain into specific structures like alpha-helices (right-handed helix) or beta-sheets.
These structures are stabilized by hydrogen bonds between the backbone of the amino acids.

Tertiary Structure

Represents the further folding of the protein chain into a three-dimensional shape.
This structure is critical for the protein's biological function.
Stabilized by various interactions like hydrophobic interactions, ionic bonds, and disulfide bridges.

Quaternary Structure

Formed when two or more polypeptide chains (subunits) assemble to form a functional protein.
The arrangement of these subunits determines the protein's quaternary structure.
Example: Human hemoglobin consists of four subunits (two alpha and two beta chains).

Structure

Enzymes

General Characteristics

Enzymes are primarily proteins, although some nucleic acids also act as enzymes (ribozymes).
They catalyze biochemical reactions without being consumed in the process.

Structure of Enzymes

Possess primary, secondary, and tertiary structures similar to other proteins.
The tertiary structure creates unique sites known as active sites.
An active site is a specific pocket or crevice where substrate molecules bind.

Function and Specificity

The active site's unique shape ensures that only specific substrates can bind, ensuring enzyme specificity.
The binding of substrates to the active site facilitates the catalytic process, speeding up reactions.

Temperature Sensitivity

Most enzymes are efficient at moderate temperatures (below 40°C) and can be denatured at high temperatures.
Enzymes from thermophilic organisms (living in extremely high temperatures) are exceptions, remaining stable and active even at temperatures up to 80°-90°C.

Importance in Biological Systems

Essential for various biochemical reactions within living organisms.
Play a crucial role in processes like digestion, metabolism, DNA replication, and more.

Chemical Reactions

Types of Chemical Changes

Physical Change: Alteration in shape or state without breaking bonds, like ice melting into water.
Chemical Reaction: Involves breaking and forming of bonds to transform substances, e.g., Ba(OH)2 + H2SO4 → BaSO4 + 2H2O.

Rate of Reactions

Defined as the amount of product formed per unit time.
Influenced by factors like temperature; rate generally doubles or halves with every 10°C change.

Role of Enzymes in Catalysis

Enzymes significantly accelerate reaction rates compared to uncatalysed reactions.
Example: Carbonic anhydrase increases the formation rate of H2CO3 from a few hundred molecules per hour to 600,000 molecules per second.

Enzyme Specificity

Each enzyme catalyzes a unique chemical or metabolic reaction.
Thousands of enzyme types exist, each facilitating specific reactions.

Metabolic Pathways

A series of enzyme-catalyzed reactions leading to a specific product.
Example: Conversion of glucose to pyruvic acid involves multiple enzymatic steps.
Products can vary based on conditions: lactic acid in anaerobic conditions, pyruvic acid in aerobic conditions, and ethanol during fermentation in yeast.

How do Enzymes bring about such High Rates of Chemical Conversions?

Active Site and Substrate Interaction

Substrates (S) interact with enzymes at the 'active site', forming an ES (Enzyme-Substrate) complex.
The substrate must diffuse towards the active site for the reaction to occur.

Transition State and ES Complex

The ES complex formation is transient.
During the reaction, the substrate transforms into a 'transition state structure' before converting into the product (P).

Energy Dynamics in Enzymatic Reactions

The potential energy content changes throughout the reaction.
The graph (y-axis: potential energy, x-axis: reaction progress) illustrates energy levels of substrate, transition state, and product.

Activation Energy and Enzyme Function

Activation energy: The energy required to convert S to the transition state.
Enzymes lower the activation energy, easing the transition from S to P.

Exothermic and Endothermic Reactions

If P has lower energy than S, the reaction is exothermic (energy-releasing).
Enzymes facilitate both exothermic (spontaneous) and endothermic (energy-requiring) reactions by reducing the activation energy.

Graph

Nature of Enzyme Action

Enzyme-Substrate Complex Formation

Enzymes (E) have specific binding sites for substrates (S).

The combination of E and S forms a highly reactive enzyme-substrate complex (ES).

Transition to Enzyme-Product Complex

ES complex is temporary and transitions into an enzyme-product complex (EP).

This process involves breaking down the substrate's chemical bonds.

Steps in Enzymatic Action

Substrate Binding: Substrate attaches to the enzyme's active site.
Induced Fit: The enzyme changes shape for a tighter fit around the substrate.
Catalysis: The active site facilitates the breakdown of substrate bonds, forming EP.
Product Release: Enzyme releases products, regenerates, and is ready to bind another substrate.

Reusability of Enzymes

Post-reaction, the unchanged enzyme can bind to a new substrate, repeating the catalytic cycle.

Factors Affecting Enzyme Activity

Temperature Influence

Optimal Temperature: Each enzyme has an ideal temperature for maximal activity.
Effect of High Temperature: Excessive heat can denature the enzyme, altering its structure and function.
Low Temperature Impact: Reduced temperature slows down enzyme activity.

pH Level Impact

Optimal pH: Specific pH level at which an enzyme operates most efficiently.
Variations in pH: Changes can lead to denaturation or reduced enzyme activity.

Substrate Concentration

Rate of Reaction: Increases with higher substrate concentration up to a saturation point.
Saturation Point: Enzyme activity levels off as all active sites are occupied.

Chemical Regulators

Inhibitors: Chemicals that decrease enzyme activity.
Activators: Compounds that increase enzyme efficiency.

Enzyme Structure Stability

Tertiary Structure: Vital for enzyme activity; changes can impact function.

Temperature and pH

Optimum Temperature and pH

Optimum Temperature: The specific temperature at which an enzyme exhibits peak activity.
Optimum pH: The specific pH level where an enzyme is most active.

Impact of Temperature on Enzymes

Low Temperature: Causes enzymes to be temporarily inactive but does not destroy them.
High Temperature: This leads to the denaturation and loss of enzymatic activity, as proteins are sensitive to heat.

Effect of pH on Enzymes

pH Variations: Changes in pH can alter the ionization of side chains in enzymes, affecting their shape and function.
Narrow pH Range: Enzymes typically function effectively within a limited pH range.

Enzyme Activity Trends

Decline in Activity: Both higher and lower than optimum temperatures and pH levels reduce enzyme activity.
Preservation and Destruction: Low temperatures preserve enzyme structure, while high temperatures can irreversibly damage it.

Concentration of Substrate

Effect of Substrate Concentration

Initial Increase in Velocity: As substrate concentration rises, enzyme reaction speed increases.
Maximum Velocity (Vmax): A point where further increase in substrate concentration doesn't enhance reaction velocity.
Enzyme Saturation: Occurs when all enzyme molecules are occupied, and no additional substrate can be processed.

Enzyme Inhibition

Inhibitors: Specific chemicals that bind to enzymes and reduce their activity.
Types of Inhibition:

Competitive Inhibition: Inhibitor resembles the substrate and competes for the active site.
Non-competitive Inhibition: Inhibitor binds elsewhere on the enzyme, altering its function.

Effect on Enzyme Activity: Leads to a decline in enzyme action due to substrate's inability to bind.

Competitive Inhibition

Mechanism: Inhibitor competes with the substrate for the active site of the enzyme.
Example: Malonate inhibiting succinic dehydrogenase, resembling the substrate succinate.
Use in Medicine: Competitive inhibitors are often used to control bacterial pathogens.

Impact on Enzyme-Catalyzed Reactions

Inhibition Dynamics: Presence of inhibitors can significantly alter the rate and efficacy of enzyme-catalyzed reactions.
Enzyme Efficiency: The efficiency of an enzyme is affected by the relative concentrations of substrate and inhibitor.

Diagram

Classification and Nomenclature of Enzymes

Overview of Enzyme Classification

Enzymes are categorized into 6 major classes, each with several subclasses.
Classification is based on the type of reaction they catalyze.
Each enzyme is assigned a unique four-digit number as per its class.

Classes of Enzymes

Oxidoreductases/Dehydrogenases

Catalyze oxidation-reduction reactions.

Example reaction: S reduced + S’ oxidised → S oxidised + S’ reduced.

Transferases

Facilitate the transfer of a group (other than hydrogen) between substrates.

Example reaction: S - G + S’ → S + S’ - G.

Hydrolases

Catalyze the hydrolysis of various bonds (ester, ether, peptide, etc.).

Lyases

Remove groups from substrates by methods other than hydrolysis, forming double bonds.

Isomerases

Catalyze the inter-conversion of isomers (optical, geometric, positional).

Ligases

Catalyze the joining of two molecules, forming bonds like C-O, C-S, C-N, P-O, etc.

Significance of Enzyme Classification

Provides a systematic way to identify and categorize enzymes.
Helps in understanding the specific function and mechanism of each enzyme.
Essential for studying metabolic pathways and enzyme kinetics.

Co-factors

Definition and Role of Co-factors

Co-factors are non-protein constituents vital for the catalytic activity of enzymes.
They bind to the protein portion (apoenzyme) of enzymes, making them catalytically active.

Types of Co-factors

Prosthetic Groups

Organic compounds, tightly bound to the apoenzyme.

Integral part of the enzyme's active site.

Example: Haem in peroxidase and catalase enzymes.

Co-enzymes

Organic, transiently associating during catalysis.

Involved in various enzyme-catalyzed reactions.

Often derived from vitamins, e.g., NAD (from niacin).

Metal Ions

Form coordination bonds with enzyme active site and substrate.

Essential for the activity of some enzymes.

Example: Zinc in carboxypeptidase.

Importance of Co-factors

Crucial for the structural stability and functionality of enzymes.
Removal of co-factor leads to loss of catalytic activity, confirming their significance.
Enhances the enzyme's ability to bind with substrates and catalyze reactions.

Summary

Chemical Similarity in Living Systems

Elemental composition of living tissues and non-living matter is qualitatively similar.
Living systems have a higher relative abundance of carbon, hydrogen, and oxygen.

Abundant Chemicals in Organisms

Water is the most prevalent chemical in living organisms.

Small Molecular Weight Biomolecules

Includes amino acids, monosaccharides, disaccharides, fatty acids, glycerol, nucleotides, nucleosides, and nitrogen bases.
There are 20 types of amino acids and 5 types of nucleotides.

Fats and Oils

Composed of glycerides; fatty acids esterified to glycerol.
Phospholipids contain a phosphorylated nitrogenous compound in addition to the standard components.

Macromolecules in Living Systems

Main macromolecules: Proteins, nucleic acids, and polysaccharides.
Lipids are grouped with macromolecules due to their association with membranes.

Hierarchy of Biomacromolecular Structures

Biomacromolecules exhibit primary, secondary, tertiary, and quaternary structures.

Roles of Nucleic Acids and Proteins

Nucleic acids (DNA and RNA) function as genetic material.
Proteins vary in function: enzymes, antibodies, receptors, hormones, structural components.
Collagen and RuBisCO are examples of abundant proteins.

Enzymes: Function and Characteristics

Catalyze biochemical reactions, exhibit substrate specificity.
Require optimum temperature and pH, get denatured at high temperatures.
Lower activation energy and increase reaction rates.

Ribozymes

Nucleic acids that also function as catalysts.

Chapter 10 - Cell Cycle and Cell Division

Introduction

Start of Life in Organisms

All organisms, regardless of size, begin life from a single cell.

Cell Growth and Reproduction

Cells exhibit two key characteristics: growth and reproduction.

Cellular reproduction involves division, where a single cell divides to form two daughter cells.

Cell Division Process

Each parental cell divides to produce two daughter cells.

These daughter cells are capable of further growth and division.

Formation of Cell Populations

Continuous cycles of growth and division enable the formation of a population from a single cell.

This process results in structures consisting of millions of cells.

Significance in Multicellular Organisms

The division of a single cell into many cells is fundamental to the development of multicellular organisms.

Cell Cycle

Overview of Cell Cycle

The cell cycle is the sequence of events where a cell duplicates its genome, synthesizes cellular components, and divides into two daughter cells.

Key Processes in Cell Cycle

DNA replication: Duplication of the cell's genetic material.

Cell growth: Increase in cytoplasmic components.

Cell division: Process of forming two daughter cells.

Coordination in Cell Cycle

These processes are coordinated to ensure accurate division and formation of genetically intact progeny cells.

Phases of Cell Cycle

The cell cycle consists of specific stages for different activities:

DNA synthesis happens in a specific stage.
Chromosome segregation and cell division occur in distinct phases.

Genetic Control

The events in the cell cycle are regulated by genetic mechanisms to ensure proper cell division.

Phases of Cell Cycle

Overview of Cell Cycle Phases

The cell cycle is categorized into two main phases: the Interphase and the M Phase (Mitosis phase).

M Phase (Mitosis Phase)

This phase involves actual cell division, including nuclear division (karyokinesis), and typically ends with cytoplasm division (cytokinesis).

Interphase

Occupying over 95% of the cell cycle's duration, it's a period of cell growth and DNA replication.
Comprises three sub-phases:

G1 Phase (Gap 1): The cell grows metabolically but does not replicate DNA.

S Phase (Synthesis): DNA replication occurs, doubling the DNA content from 2C to 4C, but chromosome number remains constant (2n).

G2 Phase (Gap 2): Continued cell growth and protein synthesis in preparation for mitosis.

G0 Phase (Quiescent Stage)

Some cells exit the G1 phase and enter this non-dividing, metabolically active stage.
They can re-enter the cell cycle under certain conditions.

Cell Division Variability

Duration of the cell cycle varies across organisms and cell types (e.g., 90 minutes in yeast vs. 24 hours in human cells).
In animals, typically seen in diploid somatic cells; exceptions include haploid cells in some species (e.g., male honey bees).
In plants, mitosis occurs in both haploid and diploid cells.

M Phase

Overview of M Phase

The M Phase is a critical and dramatic period in the cell cycle, marked by extensive cellular reorganization.
Also known as equational division since the number of chromosomes remains consistent between parent and progeny cells.

Stages of Karyokinesis

Karyokinesis, or nuclear division, is categorized into four main stages:

Prophase:

Chromosomes condense and become visible.

The nuclear envelope disintegrates.

Spindle fibers start to form.

Metaphase:

Chromosomes align at the cell's equatorial plate.

Spindle fibers attach to the centromeres of chromosomes.

Anaphase:

Chromatids separate and move to opposite poles of the cell.

This segregation ensures each new cell receives an equal and complete set of chromosomes.

Telophase:

Chromosomes reach opposite poles and decondense.

Nuclear envelopes reform around the two sets of chromosomes.

Cytokinesis may begin, dividing the cell cytoplasm into two daughter cells.

Progressive Nature of Mitosis

Mitosis is a continuous process without distinct boundaries between stages.
The transition from one stage to another is smooth and systematic.

Prophase

Introduction to Prophase

Prophase is the initial stage of mitosis, following the S and G2 phases of interphase.

Key Processes in Prophase

Chromatin Condensation:

Chromosomal material starts condensing to form visible, compact mitotic chromosomes.

Initially intertangled DNA becomes distinct.

Chromosome Structure:

Each chromosome is composed of two identical sister chromatids joined at a region called the centromere.

Centrosome Movement:

Centrosomes, duplicated during the S phase, begin migrating toward opposite poles of the cell.

Formation of Mitotic Apparatus:

Radiating microtubules from centrosomes, known as asters, contribute to the formation of the mitotic apparatus.

Spindle fibers, along with asters, facilitate chromosome movement.

Disappearance of Cellular Structures:

By the end of prophase, several cellular structures become invisible under the microscope, including:

Golgi apparatus
Endoplasmic reticulum
Nucleolus
Nuclear envelope

Metaphase

Introduction to Metaphase

Metaphase is the second phase of mitosis, following the completion of prophase.

Characteristics of Metaphase

Chromosomal Alignment:

Chromosomes, fully condensed, are aligned at the cell's equator, forming the metaphase plate.

Structure of Chromosomes:

Each metaphase chromosome consists of two sister chromatids connected at the centromere.

Kinetochores, small disc-shaped structures, form at the centromere surface.

Spindle Fibre Attachment:

Spindle fibres emerging from centrosomes attach to kinetochores of chromosomes.

Each sister chromatid is connected to spindle fibres from opposite poles.

Key Features of Metaphase:

The key elements of metaphase include:

Attachment of spindle fibres to chromosomes' kinetochores.

Alignment of chromosomes along the metaphase plate.

Equal positioning of chromosomes between the two poles

Anaphase

Introduction to Anaphase

Anaphase follows metaphase in the cell cycle and is critical for chromosome separation and distribution.

Key Events in Anaphase

Separation of Chromatids:

Chromosomes arranged at the metaphase plate split into two daughter chromatids.

Each chromatid is now considered an individual daughter chromosome.

Movement of Chromatids:

The separated daughter chromosomes begin to move towards the cell's opposite poles.

Movement is facilitated by the spindle apparatus.

Centromere Orientation:

As the chromatids move, the centromere of each chromosome leads the movement towards the poles, with the arms trailing behind.

Characteristics of Anaphase:

The key characteristics of anaphase include:

Simultaneous splitting of the centromeres of each chromosome.

Segregation of the sister chromatids to opposite poles of the cell.

Daughter chromosomes moving centromere-first towards the poles.

Telophase

Introduction to Telophase

Telophase is the final phase of karyokinesis in mitosis, marking the end of chromosomal segregation.

Key Events in Telophase

Chromosomes at Poles:

The separated chromosomes, having reached the poles, start to decondense.

The distinct identity of individual chromosomes becomes indistinct as they form chromatin clusters.

Reformation of Nuclear Envelope:

Around each set of chromatin at the poles, a new nuclear envelope forms, creating two daughter nuclei.

Reappearance of Nuclear Components:

The nucleolus, along with other organelles like the Golgi complex and the endoplasmic reticulum, reappears within the newly formed nuclei.

Characteristics of Telophase:

Loss of individuality of chromosomes as they decondense.
Formation of two distinct daughter nuclei.
Re-establishment of nuclear structures.

Cytokinesis

Introduction to Cytokinesis

Cytokinesis is the process of cytoplasmic division that follows karyokinesis (nuclear division in mitosis), resulting in the formation of two daughter cells.

Cytokinesis in Animal Cells

Furrow Formation:

Begins with the appearance of a furrow in the plasma membrane.

Deepening of the Furrow:

The furrow deepens gradually, progressing towards the center of the cell.

Completion of Division:

The furrow eventually joins in the center, splitting the cell cytoplasm into two, resulting in two separate daughter cells.

Cytokinesis in Plant Cells

Cell Wall Constraints:

Due to the presence of a rigid cell wall, plant cells undergo cytokinesis differently from animal cells.

Cell-Plate Formation:

Begins with the formation of a cell plate in the center of the cell.

Outward Growth:

The cell plate grows outward towards the existing cell walls.

New Cell Wall Formation:

The cell plate eventually becomes the middle lamella, leading to the formation of new cell walls between the two daughter cells.

Organelle Distribution:

During cytokinesis, organelles like mitochondria and plastids are evenly distributed between the two daughter cells.

Special Cases:

In some organisms, karyokinesis is not followed by cytokinesis, leading to a multinucleate condition known as syncytium (e.g., in the liquid endosperm of coconut).

Significance of Mitosis

Overview of Mitosis:

Mitosis, also known as equational division, is typically observed in diploid cells but can occur in haploid cells in certain lower plants and social insects.

Production of Diploid Daughter Cells:

Genetic Identity:

Mitosis results in diploid daughter cells with identical genetic compositions.

Role in Growth:

Contributes to the growth of multicellular organisms.

Nucleo-Cytoplasmic Ratio:

Ensures the maintenance of the nucleo-cytoplasmic ratio by dividing the cell when it grows.

Cell Repair and Replacement:

Mitosis plays a crucial role in replacing cells in various parts of the body, such as:

Skin Cells: Replaces cells in the upper layer of the epidermis.

Gut Lining Cells: Replaces cells in the lining of the gastrointestinal tract.

Blood Cells: Constant replacement of various blood cells.

Continuous Plant Growth:

In plants, mitotic divisions in meristematic tissues like the apical meristem and lateral cambium facilitate continuous growth throughout the plant's life.

Examples in Insects:

Some insects exhibit haploid and diploid phases where mitosis occurs in both stages.

Meiosis

Introduction to Meiosis:

Meiosis is a specialized cell division process forming haploid gametes, essential in sexual reproduction.

Key features:

Two sequential divisions (Meiosis I and II) with a single DNA replication phase.

Formation of four haploid cells at the end.

Significance of Meiosis:

Produces haploid gametes, ensuring genetic diversity through recombination.

Maintains the diploid chromosome number in sexually reproducing organisms by halving the chromosome number in gametes, which is restored during fertilization.

Stages of Meiosis:

Meiosis I:

Prophase I: Pairing of homologous chromosomes and crossing over/recombination occurs.

Metaphase I: Homologous chromosomes align at the equatorial plate.

Anaphase I: Separation of homologous chromosomes to opposite poles.

Telophase I: Chromosomes reach poles; the cell divides leading to two haploid cells.

Meiosis II:

Resembles mitotic division.

Prophase II: Chromosomes condense again.

Metaphase II: Chromosomes align at the equatorial plate.

Anaphase II: Separation of sister chromatids to opposite poles.

Telophase II: Chromatids reach poles; followed by cytokinesis, resulting in four haploid cells.

Importance of Recombination:

Recombination during Prophase I increases genetic variation in offspring.

Applications in Gametogenesis:

Meiosis is crucial in gametogenesis in plants and animals, leading to the formation of eggs and sperm.

Meiosis I

Prophase I

Overview of Prophase I:

Prophase I is a complex and lengthy phase of meiosis, divided into five stages: Leptotene, Zygotene, Pachytene, Diplotene, and Diakinesis.

Significant for chromosomal pairing, recombination, and preparing for chromosome segregation.

Stages of Prophase I:

Leptotene:

Chromosomes begin to condense and become visible under a microscope.

Compaction of chromosomes continues throughout this stage.

Zygotene:

Chromosomes start pairing together in a process called synapsis, forming homologous pairs.

Formation of the synaptonemal complex occurs, aiding in chromosome pairing.

Pachytene:

Chromatids of homologous chromosomes become distinct, visible as tetrads.

Recombination nodules appear, indicating sites of crossing over.

Genetic material exchange between homologous chromosomes occurs, mediated by recombinase enzyme.

Diplotene:

Dissolution of the synaptonemal complex, chromosomes start to separate except at crossover sites.

Formation of X-shaped structures called chiasmata.

Diplotene may last for extended periods in some vertebrate oocytes.

Diakinesis:

Terminalisation of chiasmata, indicating the end of crossing over.

Chromosomes fully condense, and meiotic spindle forms.

Nuclear envelope disintegrates, leading to the transition to metaphase.

Key Processes:

Synapsis: Pairing of homologous chromosomes.

Crossing over: Exchange of genetic material for genetic recombination.

Chiasmata formation: Physical manifestation of crossover between homologous chromosomes.

Significance:

Prophase I is crucial for genetic variation through recombination.

Prepares chromosomes for segregation during meiosis.

Metaphase I

Overview of Metaphase I:

Metaphase I is a critical phase of meiosis where chromosomes align for separation.

Key Events in Metaphase I:

Chromosome Alignment:

Homologous chromosomes, consisting of two sister chromatids, align at the equatorial plate of the cell.

Spindle Fiber Attachment:

Microtubules from spindle fibers emanating from opposite poles of the cell attach to the kinetochores of each homologous chromosome.

Significance of Metaphase I:

Ensures that each daughter cell receives one chromosome from each homologous pair.

Prepares chromosomes for segregation into two new cells.

Visualization of Metaphase I:

Homologous chromosomes are lined up in the middle of the cell, preparing for separation.

Key Differences from Mitotic Metaphase:

In meiosis, homologous chromosomes align as pairs (bivalents), whereas in mitosis individual duplicated chromosomes line up.

Anaphase I

Overview of Anaphase I:

Anaphase I is a crucial stage in meiosis I where homologous chromosomes are segregated.

Key Features of Anaphase I:

Separation of Homologous Chromosomes:

Homologous chromosomes, each made up of two sister chromatids, move to opposite poles of the cell.

Retention of Sister Chromatid Connection:

Unlike mitosis, sister chromatids remain connected at their centromeres.

Significance of Anaphase I:

This phase is essential for genetic diversity as it contributes to the independent assortment of chromosomes.

It reduces the chromosome number by half, setting the stage for the formation of haploid cells.

Chromosome Movement:

Spindle fibers contract, pulling homologous chromosomes apart.

Comparison with Mitosis:

In mitosis, sister chromatids separate, but in Anaphase I of meiosis, they stay together.

Telophase I

Overview of Telophase I:

Telophase I is a stage in meiosis I where the cell prepares for the division into two daughter cells, called dyads.

Key Features of Telophase I:

Reappearance of Nuclear Components:

Nuclear membrane and nucleolus re-form around the separated chromosomes.

Chromosome State:

Chromosomes may decondense slightly but do not reach the fully extended interphase state.

Cytokinesis:

Division of the cell's cytoplasm occurs, leading to the formation of two distinct daughter cells.

Formation of Dyads:

Resulting cells are termed dyads, each containing a haploid set of chromosomes.

Interkinesis:

A short-lived stage between meiosis I and II.
Notable for the absence of DNA replication.

Transition to Meiosis II:

The cell quickly progresses to prophase II, which is simpler compared to prophase I.

Significance of Telophase I:

Essential for reducing chromosome number by half, setting up for the second meiotic division.
Crucial for ensuring each daughter cell receives a complete set of chromosomes.

Meiosis II

Prophase II

Overview of Prophase II:

Prophase II marks the beginning of the second meiotic division, following immediately after cytokinesis from meiosis I.

Characteristics of Prophase II:

Timing and Transition:

Initiated right after cytokinesis, often before chromosomes have fully elongated from their previous division.

Comparison with Mitosis:

Resembles a typical mitotic division, contrasting with the more complex events of meiosis I.

Chromosomal Changes:

Chromosomes, which may have been slightly relaxed post-meiosis I, start to condense again.

Nuclear Membrane:

The nuclear membrane disintegrates, allowing the chromosomes to prepare for segregation.

Significance of Prophase II:

Prepares the cell for the second round of division, which is critical for achieving the final haploid chromosome set.

Context in Meiosis:

Serves as a transition between the chromosome number reduction in meiosis I and the final segregation of sister chromatids in meiosis II.

Metaphase II

Overview of Metaphase II:

Metaphase II is a critical phase in meiosis II, similar to metaphase in mitosis.

Key Features of Metaphase II:

Chromosomal Alignment:

Chromosomes line up at the cell's equatorial plane, central to the cell.

Microtubule Attachment:

Microtubules from the spindle fibers extend from opposite poles of the cell.

Each microtubule attaches to the kinetochore of sister chromatids.

Significance of Chromosomal Arrangement:

Ensures that each daughter cell will receive one chromatid from each chromosome.

Comparison with Metaphase I:

Unlike metaphase I, where homologous chromosomes line up, metaphase II involves the alignment of sister chromatids.

Preparation for Next Phase:

Sets the stage for the separation of sister chromatids during anaphase II.

Anaphase II

Overview of Anaphase II:

Anaphase II marks the penultimate phase of meiosis II, crucial for ensuring each daughter cell gets an equal set of chromosomes.

Key Events in Anaphase II:

Centromere Splitting:

Each chromosome's centromere divides, separating sister chromatids.

Movement of Chromatids:

The now separated sister chromatids, referred to as daughter chromosomes, move towards opposite poles of the cell.

Role of Microtubules:

Microtubules attached to kinetochores shorten, facilitating the movement of chromosomes.

Significance of Chromatid Separation:

Ensures genetic diversity and equal distribution of genetic material to the resulting daughter cells.

Preparation for Final Phase:

Sets the stage for telophase II and the eventual completion of meiosis II.

Telophase II

Overview of Telophase II:

Telophase II is the concluding phase of meiosis II, pivotal in finalizing the meiotic process and resulting in four distinct haploid daughter cells.

Key Events in Telophase II:

Reformation of Nuclear Envelope:

Nuclear envelopes reform around the two sets of chromosomes at each pole of the cell.

Chromosomal Decondensation:

Chromosomes begin to decondense, transitioning from their highly condensed state.

Nucleolus Reappearance:

The nucleolus reappears within the newly formed nuclei.

Cytokinesis:

Division of the cell's cytoplasm, leading to the formation of four haploid daughter cells, also known as a tetrad.

Outcome of Meiosis II:

Results in the production of four genetically diverse haploid cells, each containing a unique set of chromosomes.

Significance of Meiosis

Purpose of Meiosis:

Meiosis is crucial for maintaining the specific chromosome number of each species through generations in sexually reproducing organisms.

Chromosome Number Reduction:

Despite conserving chromosome number across generations, meiosis intriguingly reduces the chromosome number by half.

Genetic Variability:

Meiosis significantly contributes to the genetic variability within a population. This variability is key for the evolutionary process.

Evolutionary Importance:

The variations introduced through meiosis are essential for the evolution of species, allowing adaptation and survival in changing environments.

Balancing Chromosome Numbers:

Meiosis counterbalances the doubling of chromosome numbers during sexual reproduction, ensuring stability in the genetic makeup.

Summary

Cell Theory and Cell Division:

Cells originate from preexisting cells through cell division, a fundamental concept of the cell theory.

Cell Cycle Stages:

The cell cycle comprises two main phases:

Interphase: Preparation for cell division, including:

G1 Phase: Cell growth and normal metabolic activities.

S Phase: DNA replication and chromosome duplication.

G2 Phase: Further cytoplasmic growth.

Mitosis (M Phase): Actual cell division process, divided into:

Prophase: Chromosome condensation, centriole movement, disappearance of the nuclear envelope and nucleolus, spindle fibers formation.

Metaphase: Chromosomes align at the equatorial plate.

Anaphase: Centromeres divide, chromatids move to opposite poles.

Telophase: Chromosomes decondense, nuclear membrane and nucleolus reappear.

Cytokinesis: Division of the cytoplasm, completing cell division.

Mitosis:

Mitosis is an equational division maintaining the chromosome number from parent to daughter cells.

Meiosis - Reduction Division:

Occurs in diploid cells forming gametes.
Reduces chromosome number by half, restoring it during sexual reproduction.
Divided into Meiosis I and Meiosis II.

Meiosis I: Involves homologous chromosome pairing, crossing over, and separation.
Meiosis II: Similar to mitosis, with sister chromatids separating.

Produces four haploid cells.

Section 4 - Human Physiology

Chapter 16 - Excretory Products and their Elimination

Introduction

Introduction to Excretion:

Excretion involves eliminating metabolic wastes like ammonia, urea, uric acid, carbon dioxide, water, and various ions.

Types of Nitrogenous Wastes:

Ammonia: Highly toxic, and requires a lot of water to excrete. Common in aquatic animals.

The process is called Ammonotelism.
Excreted through body surfaces or gill surfaces in fish.

Urea: Less toxic, requires less water. Common in mammals and some amphibians.

A process called Ureotelism.
Produced in the liver, and excreted by the kidneys.

Uric Acid: Least toxic, conserves water. Found in reptiles, birds, land snails, and insects.

Process called Uricotelism.
Excreted as a semi-solid paste.

Excretory Structures in Animals:

Protonephridia/Flame Cells: Found in flatworms, rotifers, some annelids, and cephalochordates like Amphioxus. Used for osmoregulation.
Nephridia: Present in earthworms and other annelids. Remove nitrogenous wastes and help in osmoregulation.
Malpighian Tubules: In most insects, including cockroaches. Involved in excretion and osmoregulation.
Antennal/Green Glands: Found in crustaceans like prawns for excretion.

Human Excretory System

Overview of the Excretory System:

Comprises kidneys, ureters, urinary bladder, and urethra.
Kidneys: Reddish-brown, bean-shaped, located between the last thoracic and third lumbar vertebrae.

Structure of Kidneys:

Size: Approximately 10-12 cm in length, 5-7 cm in width, 2-3 cm in thickness.
Weight: Averages 120-170 g in adults.
Hilum: A notch on the inner concave surface for entry of ureter, blood vessels, and nerves.
Internal Structure: Consists of an outer cortex and an inner medulla, which includes medullary pyramids extending into calyces.

Nephrons: The Functional Units

Approximately one million nephrons per kidney.
Each nephron comprises a glomerulus and a renal tubule.
Glomerulus: A cluster of capillaries formed by the afferent arteriole.

Renal Tubule Components:

Bowman's Capsule: Encloses the glomerulus.
Proximal Convoluted Tubule (PCT): Coiled tubule connected to Bowman's capsule.
Henle’s Loop: Hairpin-shaped, with descending and ascending limbs.
Distal Convoluted Tubule (DCT): Continues from the ascending limb of Henle's loop.
Collecting Duct: Receives urine from multiple DCTs and conveys it to the renal pelvis.

Types of Nephrons:

Cortical Nephrons: Majority, with a shorter loop of Henle, primarily in the cortex.
Juxta Medullary Nephrons: Fewer, with a longer loop of Henle extending deep into the medulla.

Blood Supply and Capillary Network:

Efferent Arteriole: Forms a network around the renal tubule known as peritubular capillaries.
Vasa Recta: Parallel vessel to Henle’s loop, significant in juxta medullary nephrons.

Urine Formation

Overview of Urine Formation:

Involves glomerular filtration, reabsorption, and secretion.

Occurs in different parts of the nephron.

Glomerular Filtration:

First step in urine formation.

Blood is filtered in the glomerulus.

Average filtration rate: 1100-1200 ml/min, about 1/5th of the blood from each heart ventricle.

Filtration occurs through endothelium of glomerular blood vessels, epithelium of Bowman’s capsule, and a basement membrane.

Glomerular Filtration Rate (GFR): Approximately 125 ml/minute, totaling 180 liters per day.

Regulation of GFR:

Juxtaglomerular Apparatus (JGA) plays a key role.

JGA can release renin to adjust the GFR in response to blood pressure changes.

Reabsorption:

Nearly 99% of the filtrate is reabsorbed by renal tubules.

Substances like glucose, amino acids, and Na+ are actively reabsorbed.

Nitrogenous wastes are absorbed passively.

Water reabsorption occurs passively in initial segments of nephron.

Tubular Secretion:

Tubular cells secrete substances like H+, K+, and ammonia into the filtrate.

Plays a crucial role in maintaining ionic and acid-base balance.

Function in the Tubules

Proximal Convoluted Tubule (PCT)

Structure of PCT:

Composed of simple cuboidal brush border epithelium.

Brush border increases surface area for reabsorption.

Reabsorption in PCT:

Responsible for reabsorbing nearly all essential nutrients.

Reabsorbs 70-80% of electrolytes and water from the filtrate.

Plays a significant role in the reabsorption process of urine formation.

Role in pH and Ionic Balance:

Maintains pH and ionic balance of body fluids.

Selectively secretes hydrogen ions and ammonia into the filtrate.

Absorbs bicarbonate (HCO3-) from the filtrate to regulate acid-base balance.

Henle’s Loop

Structure of Henle's Loop:

Comprises a descending limb and an ascending limb.
The descending limb is permeable to water but nearly impermeable to electrolytes.
The ascending limb is impermeable to water but allows electrolyte transport.

Function in Filtrate Concentration:

As filtrate moves down the descending limb, it becomes concentrated due to water permeability.
In the ascending limb, the filtrate gets diluted as electrolytes are transported to the medullary fluid.

Role in Osmolarity Maintenance:

Plays a key role in maintaining high osmolarity of the medullary interstitial fluid.
Reabsorption in the ascending limb is minimal but crucial for the counter-current mechanism.

Distal Convoluted Tubule (DCT)

Primary Functions of DCT:

Conditional reabsorption of sodium (Na+) and water.

Capable of reabsorbing bicarbonate (HCO3-) and selectively secreting hydrogen (H+), potassium (K+) ions, and ammonia (NH3).

Role in Homeostasis:

DCT plays a crucial role in maintaining pH balance in the body.

Aids in maintaining sodium-potassium balance in the blood, essential for various physiological processes.

Regulation and Significance:

DCT's functionality is conditional, adapting to the body's needs.

Important for the fine-tuning of electrolyte and fluid balance in the body.

Collecting Duct

Location and Structure:

Extends from the kidney cortex to the medulla.

An integral part of the kidney's urine-concentrating mechanism.

Water Reabsorption:

Capable of significant water reabsorption.

Vital for producing concentrated urine, crucial in water conservation.

Urea Handling:

Allows passage of small amounts of urea into the medullary interstitium.

Contributes to the osmolarity maintenance in the kidney medulla.

pH and Ionic Balance:

Plays a role in maintaining blood pH and ionic balance.

Selectively secretes hydrogen (H+) and potassium (K+) ions.

Clinical Significance:

Its functionality is vital for fluid and electrolyte balance in the body.

Impairment can lead to urinary system disorders.

Diagram

Mechanism of Concentration of the Filtrate

Role of Henle’s Loop and Vasa Recta:

Essential for producing concentrated urine in mammals.

Counter current flow in Henle’s loop and vasa recta enhances efficiency.

Counter Current Flow:

Opposite direction flow in Henle’s loop and vasa recta.

Creates a concentration gradient in the medullary interstitium.

Osmolarity Gradient:

Increases from 300 mOsmolL–1 in the cortex to about 1200 mOsmolL–1 in the inner medulla.

Gradient primarily due to NaCl and urea.

Transport of Substances:

NaCl is transported by the ascending limb of Henle’s loop and exchanged with the descending limb of the vasa recta.

Urea enters the thin segment of the ascending limb and is transported back to the interstitium by the collecting tubule.

Counter Current Mechanism:

Maintains high osmolarity in the medullary interstitium.

Facilitates water reabsorption from the collecting tubule, concentrating the urine.

Urine Concentration Capability:

Human kidneys can produce urine about four times as concentrated as the initial filtrate.

Diagram

Regulation of Kidney Functions

Role of Hormonal Feedback:

Kidneys are regulated by hormones from the hypothalamus, JGA (Juxtaglomerular Apparatus), and the heart.

Activation of Osmoreceptors:

Triggered by changes in blood volume, fluid volume, and ion concentration.

Loss of body fluid activates osmoreceptors.

Release of Antidiuretic Hormone (ADH):

ADH is released by the hypothalamus in response to fluid loss.

Increases water reabsorption from the tubules, reducing diuresis (urine production).

Influence on Blood Pressure:

ADH can constrict blood vessels, raising blood pressure.

Higher blood pressure increases GFR (Glomerular Filtration Rate).

Micturition

1. Micturition Process:

Urine Storage: Urine formed in the kidneys is stored in the urinary bladder.

Bladder Stretching: As the bladder fills, it stretches, activating stretch receptors in its walls.

CNS Involvement: Stretch receptors send signals to the CNS, which in turn sends motor messages to initiate micturition.

2. Micturition Reflex:

Reflex Mechanism: Involves contraction of bladder smooth muscles and relaxation of the urethral sphincter.

Voluntary Control: Controlled by the central nervous system, allowing for voluntary release of urine.

3. Urine Characteristics:

Volume: Average daily excretion is 1 to 1.5 liters.

Appearance: Light yellow, watery, slightly acidic (pH around 6.0), with a characteristic odor.

Urea Excretion: Approximately 25-30 grams of urea excreted daily.

4. Clinical Relevance of Urine Analysis:

Diagnosis: Urine analysis aids in diagnosing metabolic disorders and kidney malfunctions.

Indicators: Presence of glucose (Glycosuria) or ketone bodies (Ketonuria) can indicate diabetes mellitus.

5. Impact of Conditions on Urine:

Alterations: Various conditions can alter the color, consistency, pH, and composition of urine.

Monitoring: Regular monitoring of urine can provide insights into overall health and kidney function.

Role of Other Organs in Excretion

1. Lungs:

CO2 Removal: Eliminates about 200 mL of carbon dioxide per minute.

Water Vapor: Excretes significant quantities of water through respiration.

2. Liver:

Bile Secretion: Produces bile containing bilirubin, biliverdin, cholesterol, degraded hormones, vitamins, and drugs.

Digestive Waste: Most liver secretions ultimately exit the body with digestive waste.

3. Skin:

Sweat Glands: Produce sweat with NaCl, urea, and lactic acid, aiding in cooling and minor waste excretion.

Sebaceous Glands: Eliminate sterols, hydrocarbons, and waxes through sebum, providing a protective layer for the skin.

4. Saliva:

Nitrogenous Wastes: Saliva can eliminate small amounts of nitrogenous wastes.

Disorders of the Excretory System

1. Uremia:

Definition: Accumulation of urea in the blood.

Consequences: This can lead to kidney failure.

Treatment: Hemodialysis - removal of urea using an artificial kidney.

2. Hemodialysis:

Process: Blood is pumped into a dialysis machine, filtered, and returned to the body.

Dialysing Unit: Uses a cellophane tube surrounded by dialyzing fluid.

Mechanism: Removes nitrogenous wastes based on concentration gradients.

Anticoagulants: Heparin is used to prevent blood clotting during the process.

3. Kidney Transplantation:

Use: For acute renal failures.

Donor Matching: Preferably a close relative to minimize immune rejection.

Advancements: Increased success rates due to modern clinical procedures.

4. Renal Calculi:

Description: Formation of kidney stones or insoluble mass of crystallized salts (oxalates, etc.).

5. Glomerulonephritis:

Definition: Inflammation of the glomeruli in the kidney.

Summary

1. Overview of Excretory System

Components: Kidneys, ureters, urinary bladder, urethra.

Kidney Structure: Contains nephrons (over a million), divided into cortex and medulla.

2. Nephron: The Functional Unit

Glomerulus: A network of capillaries formed from afferent arterioles.

Renal Tubule: Comprises Bowman’s capsule, PCT, Henle’s loop, DCT, and connects to collecting ducts.

3. Urine Formation Processes

Glomerular Filtration: Non-selective process in glomerulus, produces filtrate in Bowman’s capsule.

GFR (Glomerular Filtration Rate): About 125 ml/min.

Reabsorption: Mainly in PCT, with selective reabsorption and secretion of substances.

4. Henle’s Loop

Function: Maintains osmolarity gradient in the kidney, vital for water reabsorption.

5. DCT and Collecting Duct

Role: Further reabsorption of water and electrolytes, helps in osmoregulation and pH balance.

6. Counter Current Mechanism

Operation: Between loop of Henle and vasa recta, concentrates the filtrate.

7. Micturition

Process: Urine storage in the bladder and controlled release through urethra.

8. Additional Excretory Roles

Skin, Lungs, Liver: Assist in excretion through sweat, CO2, and bile.

9. Regulation of Kidney Function

JGA: Regulates GFR.

Hormones: ADH (antidiuretic hormone), Aldosterone, ANF (Atrial Natriuretic Factor).

10. Disorders

Uremia: Accumulation of urea in the blood, treatable by hemodialysis.

Kidney Stones (Renal Calculi): Insoluble crystallized salts in the kidney.

Glomerulonephritis: Inflammation of kidney glomeruli.

Chapter 17 - Locomotion and Movement

Introduction

1. Movement and Locomotion in Living Beings

1.1. Movement: A Core Feature

All living beings, including animals and plants, exhibit movements.
Simple forms of movement: e.g., protoplasm streaming in Amoeba.
Complex movements: use of cilia, flagella, and tentacles in various organisms.

1.2. Human Movements

Examples include moving limbs, jaws, eyelids, tongue, etc.

2. Locomotion: A Specialized Movement

2.1. Definition

Locomotion: voluntary movements resulting in a change of place or location.

2.2. Forms of Locomotion

Walking, running, climbing, flying, swimming.

2.3. Locomotory Structures

Not necessarily different from structures used for other movements.
Examples:

Paramoecium uses cilia for feeding and locomotion.
Hydra uses tentacles for capturing prey and locomotion.

Human use of limbs for body posture changes and locomotion.

3. Relationship Between Movements and Locomotion

3.1. Interconnection

Movement and locomotion are closely related and often intertwined.
Not all movements are locomotions, but all locomotions are movements.

4. Locomotion Variability

4.1. Influencing Factors

Depends on habitat and situational demands.

4.2. Purposes of Locomotion

Searching for food, shelter, mates, suitable breeding grounds.
Adapting to favorable climatic conditions.
Escaping from predators or enemies.

Types of Movement

1. Types of Movement in the Human Body

1.1. Amoeboid Movement

Characteristics:

Exhibited by specialized cells like macrophages and leucocytes.
Involves pseudopodia formed by protoplasm streaming.
Microfilaments and cytoskeletal elements play a role.

1.2. Ciliary Movement

Characteristics:

Occurs in internal tubular organs with ciliated epithelium.
Helps in removing inhaled dust particles in the trachea.
Assists the passage of ova through the female reproductive tract.

1.3. Muscular Movement

Characteristics:

Required for moving limbs, jaws, tongue, etc.
Utilizes the contractile property of muscles.
Essential for locomotion and various other movements.

Coordination:

Involves coordinated activity of muscular, skeletal, and neural systems.

2. Understanding Human Locomotion

2.1. Importance

Integral for efficient and effective movement in multicellular organisms.

2.2. Components of Study

Types of muscles.
Muscle structure.
Mechanism of muscle contraction.
Key aspects of the skeletal system.

Muscle

1. Introduction to Muscles

1.1. Overview

Specialized tissue of mesodermal origin.
Constitute 40-50% of human adult body weight.
Properties: Excitability, Contractility, Extensibility, Elasticity.

2. Classification of Muscles

2.1. Based on Location

(i) Skeletal Muscles:

Associated with skeletal components.
Striated appearance, voluntary control.
Involved in locomotion and body posture changes.

(ii) Visceral Muscles:

Located in the walls of hollow organs (e.g., alimentary canal, reproductive tract).
Smooth, non-striated, involuntary control.

(iii) Cardiac Muscles:

Muscles of the heart.
Striated in appearance but involuntary.

3. Skeletal Muscle Structure and Mechanism

3.1. Composition

Composed of muscle bundles or fascicles.
Bundles held together by collagenous connective tissue (fascia).

3.2. Muscle Fibres

Each fiber is lined by sarcolemma, enclosing sarcoplasm.
Syncitium structure with multiple nuclei.
Sarcoplasmic reticulum as calcium ion storehouse.

3.3. Myofilaments

Parallelly arranged in sarcoplasm.
Contains two proteins: Actin (thin filaments) and Myosin (thick filaments).

3.4. Bands and Lines

I-band: Light band with actin.
A-band: Dark band with myosin.
Z-line: Elastic fiber bisecting I-band, attaching thin filaments.
M-line: Holds thick filaments in A-band.

3.5. Sarcomere

The functional unit of contraction between two Z-lines.
Alternating arrangement of A and I bands.

3.6. H-zone

The central part of the thick filament is not overlapped by thin filaments.

Structure of Contractile Proteins

1.1. Composition

Made of two filamentous ('F') actins helically wound.
'F' actin: A polymer of monomeric 'G' (Globular) actins.

1.2. Associated Proteins

Tropomyosin filaments run alongside 'F' actins.
The Troponin complex is distributed at regular intervals on the tropomyosin.

1.3. Function in Resting State

The Troponin subunit masks active binding sites for myosin on actin filaments.

2. Structure of Myosin (Thick) Filaments

2.1. Composition

Polymerized proteins are made of monomeric proteins called Meromyosins.

2.2. Meromyosin Structure

Each meromyosin has:

Globular head with a short arm (Heavy Meromyosin, HMM).
Tail (Light Meromyosin, LMM).

2.3. Cross Arms

HMM components project outwards from the myosin filament.
Known as cross arms at regular distances and angles.

2.4. Function of Globular Head

Active ATPase enzyme.
Has binding sites for ATP.
Contains active sites for actin.

Mechanism of Muscle Contraction

1. Sliding Filament Theory of Muscle Contraction

1.1. Basic Concept

Muscle contraction involves sliding of thin filaments over thick filaments.

2. Initiation of Muscle Contraction

2.1. Role of Central Nervous System (CNS)

Signal from CNS to muscle fiber via motor neuron.

2.2. Motor Unit

Consists of a motor neuron and its connected muscle fibers.

2.3. Neuromuscular Junction

Site where motor neuron and muscle fiber meet (motor-end plate).
Release of neurotransmitter (Acetylcholine) generates action potential.

3. Process of Muscle Contraction

3.1. Action Potential and Calcium Release

Action potential causes release of Ca++ into sarcoplasm.

3.2. Activation of Actin Filaments

Ca++ binds to troponin, uncovering active sites on actin.

3.3. Cross-Bridge Formation

Myosin head binds to actin, forming cross-bridge.

3.4. Sarcomere Shortening

Actin filaments pulled towards 'A' band center; 'Z' lines drawn inwards.
'I' bands shorten, while 'A' bands remain constant.

3.5. ATP Role and Muscle Relaxation

Myosin releases ADP, returns to relaxed state.
New ATP binds, breaking cross-bridge.
Ca++ pumped back, actin re-masked, muscle relaxes.

4. Muscle Fiber Types and Characteristics

4.1. Red Fibers

High myoglobin content, appear red.
Rich in mitochondria, aerobic energy generation.

4.2. White Fibers

Low myoglobin content, appear pale.
Fewer mitochondria, high sarcoplasmic reticulum.
Energy through anaerobic processes.

Skeletal System

1. Overview of Skeletal System

1.1. Composition

Framework of bones and cartilages.
Significant role in body movement.
Made of 206 bones and a few cartilages in humans.

2. Skeletal System Division

2.1. Axial Skeleton

Comprises 80 bones along the body's main axis.
Includes skull, vertebral column, sternum, and ribs.
Skull:

Made of cranial (8) and facial (14) bones, totaling 22.
Contains Ear Ossicles (Malleus, Incus, Stapes).

Vertebral Column:

26 vertebrae: cervical (7), thoracic (12), lumbar (5), sacral (1-fused), coccygeal (1-fused).
Protects spinal cord, supports head, and attaches to ribs.

Sternum and Ribs:

Sternum: Flat bone on thorax's ventral midline.
12 pairs of ribs: true ribs (1-7), vertebrochondral ribs (8-10), floating ribs (11-12).

2.2. Appendicular Skeleton

Comprises bones of limbs and girdles.
Limb Bones:

Forelimbs: Humerus, radius, ulna, carpals (8), metacarpals (5), phalanges (14).
Hindlimbs: Femur, tibia, fibula, tarsals (7), metatarsals (5), phalanges (14), patella (knee cap).

Girdles:

Pectoral Girdle: Clavicle (collar bone) and scapula.
Pelvic Girdle: Coxal bones (ilium, ischium, pubis).

3. Specific Features of Bones and Girdles

3.1. Pectoral Girdle

Scapula with acromion and glenoid cavity.
Clavicle articulates with acromion.

3.2. Pelvic Girdle

Coxal bones formed by the fusion of ilium, ischium, and pubis.
Acetabulum cavity articulates with thigh bone.
Pubic symphysis at ventral meeting point of coxal bones.

Joints

1. Importance of Joints

1.1. Role in Movement

Essential for movements involving bony parts of the body.
Critical in locomotory movements.

2. Characteristics of Joints

2.1. Definition

Points of contact between bones, or between bones and cartilages.

2.2. Function

Act as a fulcrum for muscle-generated force to carry out movement.

2.3. Mobility

Varies based on different factors.

3. Classification of Joints

3.1. Types of Joints

(i) Fibrous Joints:

Limited to no movement.

(ii) Cartilaginous Joints:

Slightly more movement than fibrous joints.

(iii) Synovial Joints:

Freely movable, the most common type in the body.

Fibrous joints

1.1. Movement

Do not allow any movement.

1.2. Characteristics

Formed by the fusion of flat skull bones end-to-end.

1.3. Composition

Dense fibrous connective tissues.

1.4. Example

Sutures in the skull form the cranium.

Cartilaginous joints

1.1. Composition

Bones joined together with cartilage.

1.2. Movement

Permit limited movements.

1.3. Example

Joint between adjacent vertebrae in the vertebral column.

Synovial joints

1.1. Characteristics

Presence of a fluid-filled synovial cavity between articulating bone surfaces.

1.2. Movement

Allows considerable movement.
Essential for locomotion and various other movements.

1.3. Examples

(i) Ball and Socket Joint:

Between the humerus and pectoral girdle.

(ii) Hinge Joint:

Knee joint.

(iii) Pivot Joint:

Between atlas and axis.

(iv) Gliding Joint:

Between carpals.

(v) Saddle Joint:

Between the carpal and metacarpal of the thumb.

Disorders of Muscular and Skeletal System

1. Disorders of Muscular and Skeletal System

1.1. Myasthenia Gravis

Description:

Autoimmune disorder affecting neuromuscular junction.

Symptoms:

Fatigue, weakening, and paralysis of skeletal muscle.

1.2. Muscular Dystrophy

Description:

Progressive degeneration of skeletal muscle, often genetic.

1.3. Tetany

Description:

Rapid muscle spasms due to low Ca++ in body fluid.

1.4. Arthritis

Description:

Inflammation of joints.

1.5. Osteoporosis

Description:

Age-related disorder with decreased bone mass and increased fracture risk.

Common Cause:

Decreased levels of estrogen.

1.6. Gout

Description:

Joint inflammation due to uric acid crystal accumulation.

Summary

1. Overview of Movement in Living Beings

1.1. Types of Movement

Protoplasmic streaming, ciliary movements, movements of fins, limbs, wings, etc.

1.2. Locomotion

Voluntary movement causing change of place, usually for survival needs.

2. Human Body Movements

2.1. Types

Amoeboid, ciliary, and muscular movements.

2.2. Muscle Coordination

Essential for locomotion and various movements.

3. Types of Muscles in the Human Body

3.1. Skeletal Muscles

Attached to skeletal elements, striated, voluntary.

3.2. Visceral Muscles

In visceral organs' walls, nonstriated, involuntary.

3.3. Cardiac Muscles

Heart muscles, striated, branched, involuntary.

3.4. Muscle Properties

Excitability, contractility, extensibility, elasticity.

4. Muscle Structure and Function

4.1. Muscle Fiber and Myofibrils

Muscle fiber contains parallel myofibrils.

4.2. Sarcomere

Functional unit in myofibrils, consists of ‘A’ and ‘I’ bands.

4.3. Actin and Myosin

Polymerised proteins; actin has masked sites for myosin.

5. Muscle Contraction and Relaxation

5.1. Mechanism

Involves Ca++ release, activation of actin, and cross-bridge formation.

5.2. Fatigue and Muscle Fiber Types

Repeated stimulation leads to fatigue.
Red and White fibers based on myoglobin content.

6. Skeletal System

6.1. Components

Bones and cartilages.

6.2. Division

Axial (skull, vertebral column, ribs, sternum) and appendicular (limbs and girdles).

7. Types of Joints

7.1. Classification

Fibrous, cartilaginous, and synovial joints.

7.2. Synovial Joints

Allow considerable movement, significant in locomotion.

Chapter 18 - Neural Control and Coordination

Introduction

1. Importance of Coordination in the Body

1.1. Role in Homeostasis

Essential for maintaining balance and functioning of the body.

1.2. Definition of Coordination

Interaction and complementation of functions among organs.

2. Example of Coordination during Physical Exercise

2.1. Increased Energy Demand

This leads to enhanced muscular activity and oxygen supply.

2.2. Body's Response

Increased respiration rate, heart rate, and blood flow.

2.3. Return to Normalcy

Post-exercise, activities of nerves, lungs, heart, and kidneys normalize.

3. Organs Involved in Exercise Coordination

3.1. Primary Organs

Muscles, lungs, heart, blood vessels, kidneys.

4. Neural and Endocrine Coordination

4.1. Neural System

Provides quick point-to-point coordination.

4.2. Endocrine System

Ensures chemical integration via hormones.

4.3. Joint Function

Both systems integrate activities for synchronized organ function.

5. Focus of Chapter

5.1. Neural System in Humans

Structure and functions.

5.2. Neural Coordination Mechanisms

Transmission of nerve impulse, impulse conduction across synapses.

Neural System

1. Overview of the Neural System

1.1. Composition

Composed of specialized cells called neurons.
Neurons detect, receive, and transmit stimuli.

2. Neural System in Different Organisms

2.1. Lower Invertebrates

Simple neural organization.
Example: Hydra with a network of neurons.

2.2. Insects

Better organized neural system.
Presence of a brain, ganglia, and neural tissues.

2.3. Vertebrates

More developed and complex neural system.

Human Neural System

1. Human Neural System

1.1. Division

Comprises two parts: the Central Neural System (CNS) and the Peripheral Neural System (PNS).

2. Central Neural System (CNS)

2.1. Components

Includes the brain and spinal cord.

2.2. Function

Site of information processing and control.

3. Peripheral Neural System (PNS)

3.1. Composition

Consists of all nerves associated with the CNS.

3.2. Types of Nerve Fibres

(a) Afferent Fibres:

Transmit impulses from tissues/organs to the CNS.

(b) Efferent Fibres:

Transmit regulatory impulses from the CNS to peripheral tissues/organs.

4. Divisions of PNS

4.1. Somatic Neural System

Transmits impulses from the CNS to skeletal muscles.

4.2. Autonomic Neural System

Transmits impulses from the CNS to involuntary organs and smooth muscles.
Further classified into:

Sympathetic Neural System
Parasympathetic Neural System

5. Visceral Nervous System

5.1. Composition

Part of the PNS includes nerves, fibres, ganglia, and plexuses.

5.2. Function

Facilitates impulse travel between the CNS and the viscera.

Neurons as Structural and Functional Units of Neural System

1. Neuron: Basic Structure

1.1. Components

Composed of cell body, dendrites, and axon.

1.2. Cell Body

Contains cytoplasm, cell organelles, and Nissl’s granules.

2. Dendrites

2.1. Description

Short fibers with Nissl’s granules, branching out of the cell body.

2.2. Function

Transmit impulses towards the cell body.

3. Axon

3.1. Structure

Long fiber with a branched distal end.

3.2. Synaptic Knob

Termination of axon branches as bulb-like structures.
Contains synaptic vesicles with neurotransmitters.

3.3. Function

Transmit nerve impulses away from the cell body.

4. Types of Neurons

4.1. Multipolar Neurons

One axon and two or more dendrites; in the cerebral cortex.

4.2. Bipolar Neurons

One axon and one dendrite; in the retina of the eye.

4.3. Unipolar Neurons

One axon; is typically found in embryonic stages.

5. Axon Types

5.1. Myelinated Nerve Fibres

Enveloped by Schwann cells forming a myelin sheath.
Nodes of Ranvier between adjacent myelin sheaths.
Present in spinal and cranial nerves.

5.2. Unmyelinated Nerve Fibres

Enclosed by a Schwann cell without forming a myelin sheath.
Found in autonomous and somatic neural systems.

Generation and Conduction of Nerve Impulse

1. Neuron Excitability and Polarisation

1.1. Polarised Membrane State

Neurons are excitable with polarised membranes.

1.2. Ion Channels

Selectively permeable to different ions.

1.3. Resting State

High permeability to K+, low to Na+, impermeable to negative proteins.

2. Maintenance of Ionic Gradient

2.1. Ion Concentrations

High K+, low Na+ inside; opposite outside the axon.

2.2. Sodium-Potassium Pump

Actively transports 3 Na+ out and 2 K+ in.

2.3. Membrane Polarisation

Positive charge outside, negative inside, creating resting potential.

3. Generation of Nerve Impulse

3.1. Stimulus Application

Causes increased Na+ permeability at the stimulation site.

3.2. Depolarisation

Reversal of membrane polarity; outside becomes negative.

3.3. Action Potential

Electrical potential difference at the site, termed as nerve impulse.

4. Conduction of Nerve Impulse

4.1. Propagation Mechanism

The impulse travels along the axon by sequential depolarization.

4.2. Restoration of Resting Potential

K+ permeability rises, diffuses outside, and resets resting potential.

4.3. Responsiveness

Fiber becomes responsive to further stimulation post-restoration.

Transmission of Impulses

1. Synapses: Junctions for Impulse Transmission

1.1. Definition

Junctions where nerve impulses are transmitted from one neuron to another.

1.2. Components

Formed by pre-synaptic and post-synaptic neuron membranes.

2. Types of Synapses

2.1. Electrical Synapses

Characteristics:

Pre- and post-synaptic membranes are very close.
Direct flow of electrical current between neurons.

Impulse Transmission:

Similar to conduction along a single axon.
Faster than chemical synapses.

2.2. Chemical Synapses

Characteristics:

Separated by synaptic cleft.
Involves neurotransmitters for impulse transmission.

Mechanism:

Neurotransmitters are released from vesicles in axon terminals.
Bind to specific receptors on the post-synaptic membrane.

Outcome:

Opens ion channels, generating new potential in post-synaptic neurons.
Potential can be excitatory or inhibitory.

Central Neural System

1. Brain: The Command and Control System

1.1. Functions

Controls voluntary movements and balance.
Regulates the functioning of vital involuntary organs (lungs, heart, kidneys).
Manages thermoregulation, hunger, thirst, and circadian rhythms.
Coordinates activities of endocrine glands and various aspects of human behavior.
Processing center for vision, hearing, speech, memory, intelligence, emotions, and thoughts.

2. Protection and Covering of the Brain

2.1. Skull

Encases and protects the brain.

2.2. Cranial Meninges

Layers:

Dura Mater: Outer layer.
Arachnoid: Thin middle layer.
Pia Mater: Inner layer in contact with brain tissue.

3. Major Parts of the Brain

3.1. Division

Divided into three parts: Forebrain, Midbrain, and Hindbrain.

Forebrain

1. Forebrain Composition

1.1. Constituents

Consists of the cerebrum, thalamus, and hypothalamus.

2. Cerebrum

2.1. Structure

Largest part of the brain.
Divided longitudinally into left and right cerebral hemispheres.
Connected by corpus callosum.

2.2. Cerebral Cortex

Outer layer, known as grey matter.
Contains neuron cell bodies.
Includes motor areas, sensory areas, and association areas.

2.3. Functions of Association Areas

Complex functions like memory and communication.

2.4. White Matter

Inner part with myelin sheath, giving white appearance.

3. Thalamus

3.1. Role

Major coordinating center for sensory and motor signaling.

3.2. Location

Enclosed by the cerebrum.

4. Hypothalamus

4.1. Functions

Regulates body temperature, hunger, and thirst.
Contains neurosecretory cells producing hypothalamic hormones.

4.2. Location

Situated at the base of the thalamus.

5. Limbic System

5.1. Composition

Includes inner parts of cerebral hemispheres, amygdala, hippocampus.

5.2. Functions

Regulation of sexual behavior, emotional reactions, and motivation.

Midbrain

1. Midbrain Overview

1.1. Location

Situated between the thalamus/hypothalamus of the forebrain and the pons of the hindbrain.

1.2. Cerebral Aqueduct

Contains a canal known as the cerebral aqueduct.

2. Features of the Midbrain

2.1. Dorsal Portion

Characterized by four round swellings called corpora quadrigemina.

Hindbrain

1. Hindbrain Composition

1.1. Constituents

Comprises pons, cerebellum, and medulla (medulla oblongata).

2. Pons

2.1. Structure

Contains fiber tracts interconnecting different brain regions.

3. Cerebellum

3.1. Surface

Highly convoluted to accommodate more neurons.

4. Medulla Oblongata

4.1. Connection

Links the brain to the spinal cord.

4.2. Functions

Controls respiration, cardiovascular reflexes, and gastric secretions.

5. Brain Stem

5.1. Composition

Formed by the midbrain, pons, and medulla oblongata.

5.2. Function

Provides connections between the brain and spinal cord.

Summary

1. Neural System Functions

1.1. Coordination and Integration

Coordinates functions, metabolic, and homeostatic activities of organs.

1.2. Neuron Excitability

Due to differential ion concentration across the membrane.

2. Neural Impulses

2.1. Resting Potential

The electrical potential difference across the resting neural membrane.

2.2. Conduction

Wave of depolarisation and repolarisation along the axon.

3. Synapses

3.1. Composition

Formed by pre-synaptic and post-synaptic neuron membranes.

3.2. Synaptic Cleft

Space that may or may not separate the neurons.

3.3. Neurotransmitters

Chemicals aiding impulse transmission at chemical synapses.

4. Human Neural System Parts

4.1. Central Neural System (CNS)

Comprises the brain and spinal cord.

4.2. Peripheral Neural System

Connects CNS to the body's extremities and organs.

5. Brain Division

5.1. Forebrain

Includes cerebrum, thalamus, and hypothalamus.
Controls temperature, eating, drinking, and limbic system functions.

5.2. Midbrain

Integrates visual, tactile, and auditory inputs.

5.3. Hindbrain

Comprises pons, cerebellum, and medulla.
Manages respiration, cardiovascular reflexes, and gastric secretions.

Chapter 19 - Chemical Coordination and Integration

Introduction

1. Neural System Coordination

1.1. Rapid Coordination

Provides point-to-point and rapid coordination among organs.

1.2. Characteristics

Fast but short-lived effects.

2. Limitations of Neural Coordination

2.1. Partial Innervation

Nerve fibers do not reach all body cells.

2.2. Need for Continuous Regulation

Cellular functions require constant regulation.

3. Role of Hormones

3.1. Function

Provide the needed continuous coordination and integration.

3.2. Interaction with Neural System

Hormones complement the neural system's functions.

4. Joint Coordination by Neural and Endocrine Systems

4.1. Combined Regulation

Both systems work together to regulate physiological functions in the body.

Endocrine Glands and Hormones

1. Endocrine Glands

1.1. Nature

Ductless glands.

1.2. Secretions

Produce hormones.

2. Hormones

2.1. Classical Definition

Chemicals produced by endocrine glands are released into the blood, targeting distant organs.

2.2. Current Scientific Definition

Non-nutrient chemicals act as intercellular messengers, produced in trace amounts.

2.3. Scope

Covers new molecules in addition to traditional hormones.

3. Endocrine Systems in Organisms

3.1. Invertebrates

Possess simple endocrine systems with few hormones.

3.2. Vertebrates

Have complex coordination with a large number of hormones.

3.3. Human Endocrine System

Described as having a more intricate and diverse range of hormones.

Human Endocrine System

1. Human Endocrine System Overview

1.1. Composition

Consists of endocrine glands and hormone-producing tissues/cells throughout the body.

2. Organized Endocrine Glands

2.1. Major Glands

Pituitary, pineal, thyroid, adrenal, pancreas, parathyroid, thymus.

2.2. Gonads

Testis in males and ovary in females.

3. Additional Hormone-Producing Organs

3.1. Other Organs

The gastrointestinal tract, liver, kidney, and heart also produce hormones.

4. Scope of Study

4.1. Focus

Structure and functions of major endocrine glands and hypothalamus

The Hypothalamus

1. Hypothalamus Overview

1.1. Location

Basal part of the diencephalon, in the forebrain.

1.2. Functions

Regulates a wide spectrum of body functions.

2. Hormone Production by Hypothalamus

2.1. Neurosecretory Cells

Contains nuclei that produce hormones.

2.2. Role in Pituitary Regulation

Regulates synthesis and secretion of pituitary hormones.

3. Types of Hypothalamic Hormones

3.1. Releasing Hormones

Stimulate secretion of pituitary hormones.

3.2. Inhibiting Hormones

Inhibit secretions of pituitary hormones.

3.3. Examples

Gonadotrophin-releasing hormone (GnRH) stimulates gonadotrophins.
Somatostatin inhibits growth hormone release.

4. Hormonal Pathways

4.1. Transportation to Pituitary

Hormones travel via axons and portal circulatory system to the pituitary.

4.2. Regulation of Anterior Pituitary

Hypothalamic hormones regulate anterior pituitary functions.

4.3. Posterior Pituitary Control

Under direct neural regulation of the hypothalamus.

The Pituitary Gland

1. Pituitary Gland Location and Structure

1.1. Location

Situated in the bony cavity of sella tursica, attached to the hypothalamus.

1.2. Anatomical Division

Divided into adenohypophysis and neurohypophysis.

2. Adenohypophysis (Anterior Pituitary)

2.1. Components

Consists of pars distalis and pars intermedia.

2.2. Hormones Secreted

Growth hormone (GH), prolactin (PRL), thyroid-stimulating hormone (TSH), adrenocorticotrophic hormone (ACTH), luteinizing hormone (LH), follicle-stimulating hormone (FSH), and melanocyte-stimulating hormone (MSH).

3. Neurohypophysis (Posterior Pituitary)

3.1. Function

Stores and releases oxytocin and vasopressin (synthesized by the hypothalamus).

4. Hormone Functions and Disorders

4.1. Growth Hormone (GH)

Over-secretion leads to gigantism; under-secretion results in dwarfism.
Acromegaly caused by excess GH in adults.

4.2. Prolactin (PRL)

Regulates mammary gland growth and milk formation.

4.3. Thyroid-Stimulating Hormone (TSH)

Stimulates thyroid hormone production.

4.4. Adrenocorticotrophic Hormone (ACTH)

Stimulates glucocorticoids production in adrenal cortex.

4.5. Gonadotrophins (LH and FSH)

LH: Stimulates androgen production in males, ovulation, and corpus luteum maintenance in females.
FSH: Involved in spermatogenesis and ovarian follicle development.

4.6. Melanocyte-Stimulating Hormone (MSH)

Regulates skin pigmentation.

4.7. Oxytocin

Stimulates uterine contractions during childbirth and milk ejection.

4.8. Vasopressin (Antidiuretic Hormone, ADH)

Enhances water and electrolyte resorption in kidneys.
Deficiency causes Diabetes Insipidus.

The Pineal Gland

1. Pineal Gland Location

1.1. Position

Situated on the dorsal side of the forebrain.

2. Hormone Secretion

2.1. Melatonin

The pineal gland secretes melatonin.

3. Functions of Melatonin

3.1. Diurnal Rhythm Regulation

Crucial in regulating the 24-hour cycle of the body.

3.2. Sleep-Wake Cycle

Helps maintain normal sleep-wake rhythms.

3.3. Body Temperature Regulation

Influences body temperature patterns.

3.4. Additional Influences

Affects metabolism, pigmentation, menstrual cycle, and immune function.

Thyroid Gland

1. Thyroid Gland Anatomy

1.1. Location

Comprises two lobes on either side of the trachea, connected by the isthmus.

1.2. Composition

Made of follicles and stromal tissues.

2. Hormone Synthesis

2.1. Thyroid Hormones

Follicular cells produce tetraiodothyronine (T4) and triiodothyronine (T3).

2.2. Iodine Requirement

Essential for normal hormone synthesis.

3. Disorders Related to Thyroid Gland

3.1. Hypothyroidism

Iodine deficiency leads to goitre and reduced hormone production.
Causes cretinism, menstrual irregularities, and other health issues.

3.2. Hyperthyroidism

Overproduction of thyroid hormones, leading to physiological issues.
Includes conditions like exophthalmic goitre (Graves’ disease).

4. Functions of Thyroid Hormones

4.1. Metabolic Rate Regulation

Controls basal metabolic rate.

4.2. Support in RBC Formation

Aids in red blood cell formation.

4.3. Metabolism Control

Regulates metabolism of carbohydrates, proteins, and fats.

4.4. Water and Electrolyte Balance

Influences balance of water and electrolytes.

5. Additional Hormone

5.1. Thyrocalcitonin (TCT)

Regulates blood calcium levels.

Parathyroid Gland

1. Parathyroid Gland Location

1.1. Position

Four glands are located on the back side of the thyroid gland.

2. Hormone Secretion

2.1. Parathyroid Hormone (PTH)

Secretes PTH, a peptide hormone.

2.2. Regulation of Secretion

Secretion is regulated by blood calcium ion levels.

3. Functions of Parathyroid Hormone

3.1. Calcium Level Regulation

Increases Ca2+ levels in the blood.

3.2. Bone Resorption

Stimulates bone dissolution/demineralisation.

3.3. Renal Reabsorption

Enhances Ca2+ reabsorption by renal tubules.

3.4. Digestive Absorption

Increases Ca2+ absorption from digested food.

3.5. Hypercalcemic Hormone

PTH is hypercalcemic, raising blood Ca2+ levels.

3.6. Role in Calcium Balance

Works with thyrocalcitonin (TCT) for calcium balance in the body.

Thymus

1. Thymus Gland Location and Structure

1.1. Location

Situated between the lungs, behind the sternum, and on the ventral side of the aorta.

1.2. Structure

Lobular in form.

2. Role in Immune System Development

2.1. Immune System Development

Plays a crucial role in the maturation of the immune system.

3. Hormone Secretion

3.1. Thymosins

Secretes peptide hormones called thymosins.

4. Functions of Thymosins

4.1. T-lymphocyte Differentiation

Aids in the differentiation of T-lymphocytes for cell-mediated immunity.

4.2. Antibody Production

Promotes the production of antibodies, contributing to humoral immunity.

5. Thymus Degeneration and Immunity in Elderly

5.1. Age-Related Changes

Thymus degenerates in older individuals.

5.2. Impact on Immune Response

Leads to reduced thymosin production and weaker immune responses in the elderly.

Adrenal Gland

1. Adrenal Gland Location and Structure

1.1. Location

One gland located at the anterior part of each kidney.

1.2. Composition

Composed of adrenal medulla (central tissue) and adrenal cortex (outer layer).

2. Adrenal Medulla Hormones

2.1. Hormones Secreted

Produces adrenaline (epinephrine) and noradrenaline (norepinephrine).

2.2. Function

Respond to stress and emergency situations.
Increase alertness, heart rate, and respiration rate.

2.3. Effect on Metabolism

Stimulate glycogen breakdown, increase blood glucose, and enhance fat and protein breakdown.

3. Adrenal Cortex Layers and Hormones

3.1. Cortex Layers

Zona reticularis (inner), zona fasciculata (middle), zona glomerulosa (outer).

3.2. Corticoids Secretion

Glucocorticoids (e.g., cortisol) and mineralocorticoids (e.g., aldosterone).

4. Glucocorticoids Functions

4.1. Main Glucocorticoid

Cortisol: Stimulates gluconeogenesis, lipolysis, proteolysis.

4.2. Physiological Roles

Cardiovascular and kidney function maintenance, anti-inflammatory, immune suppression, stimulates RBC production.

5. Mineralocorticoids Functions

5.1. Main Mineralocorticoid

Aldosterone: Regulates Na+ and water reabsorption, K+ and phosphate excretion.

5.2. Effect on Body

Maintains electrolytes, body fluid volume, osmotic pressure, and blood pressure.

6. Disorders and Other Hormones

6.1. Addison’s Disease

Caused by underproduction of adrenal cortex hormones.

6.2. Androgenic Steroids

Contribute to the growth of axial, pubic, and facial hair during puberty.

Pancreas

1. Pancreas as a Composite Gland

1.1. Dual Function

Functions as both an exocrine and endocrine gland.

1.2. Endocrine Component

Contains 'Islets of Langerhans'.

2. Islets of Langerhans

2.1. Proportion in Pancreas

Represent 1 to 2 percent of pancreatic tissue.

2.2. Cell Types

α-cells secrete glucagon.
β-cells secrete insulin.

3. Hormones of the Pancreas

3.1. Glucagon

A peptide hormone, increases blood sugar (hyperglycemia).
Stimulates glycogenolysis and gluconeogenesis in the liver.

3.2. Insulin

A peptide hormone, reduces blood sugar (hypoglycemia).
Enhances glucose uptake and utilization by hepatocytes and adipocytes.
Stimulates glycogenesis.

4. Regulation of Blood Glucose

4.1. Homeostasis

Blood glucose levels maintained by insulin and glucagon.

5. Diabetes Mellitus

5.1. Condition

Caused by prolonged hyperglycemia.
Characterized by glucose loss in urine and ketone body formation.

5.2. Treatment

Managed with insulin therapy.

Testis

1. Testis: Location and Function

1.1. Location

A pair of testes located in the scrotal sac outside the abdomen in males.

1.2. Dual Function

Functions as a primary sex organ and an endocrine gland.

2. Composition of Testis

2.1. Structure

Composed of seminiferous tubules and interstitial tissue.

2.2. Leydig Cells

Located in the intertubular spaces, produce androgens (mainly testosterone).

3. Androgens and Their Functions

3.1. Hormones

Testosterone is the primary androgen produced.

3.2. Role in Male Reproductive System

Development and functioning of male accessory sex organs.

3.3. Influence on Physical Characteristics

Promote muscular growth, facial and axillary hair, aggressiveness, and deepening of voice.

3.4. Spermatogenesis

Stimulate the formation of spermatozoa.

3.5. Impact on Behavior

Affect male sexual behavior (libido).

3.6. Metabolic Effects

Anabolic effects on protein and carbohydrate metabolism.

Ovary

1. Ovary: Location and Function

1.1. Location

A pair of ovaries located in the abdomen in females.

1.2. Primary Female Sex Organ

Produces ovum during each menstrual cycle.

2. Hormone Production

2.1. Steroid Hormones

Produces estrogen and progesterone.

2.2. Structure

Composed of ovarian follicles and stromal tissues.

3. Estrogen Secretion and Functions

3.1. Synthesis

Synthesized mainly by growing ovarian follicles.

3.2. Actions

Stimulates growth of female secondary sex organs and follicle development.
Develops female secondary sex characteristics (e.g., high pitch of voice).
Regulates mammary gland development and female sexual behavior.

4. Progesterone Secretion and Functions

4.1. Source

Secreted mainly by the corpus luteum after ovulation.

4.2. Role in Pregnancy

Supports pregnancy.

4.3. Effect on Mammary Glands

Stimulates formation of alveoli and milk secretion.

Hormones of the Kidney, Heart, and Gastrointestinal Tract

1. Hormones Secreted by Non-Endocrine Tissues

1.1. Hormones Beyond Endocrine Glands

Some body tissues not classified as endocrine glands also secrete hormones.

2. Heart: Atrial Natriuretic Factor (ANF)

2.1. Secretion by Atrial Wall

Produces ANF, a peptide hormone.

2.2. Function

Decreases blood pressure by causing dilation of blood vessels.

3. Kidney: Erythropoietin

3.1. Produced by Juxtaglomerular Cells

Secretes erythropoietin, another peptide hormone.

3.2. Role

Stimulates erythropoiesis (formation of RBCs).

4. Gastrointestinal Tract Hormones

4.1. Four Major Peptide Hormones

Gastrin, secretin, cholecystokinin (CCK), and gastric inhibitory peptide (GIP).

4.2. Functions

Gastrin: Stimulates hydrochloric acid and pepsinogen secretion.
Secretin: Stimulates water and bicarbonate ion secretion in the pancreas.
CCK: Stimulates secretion of pancreatic enzymes and bile juice.
GIP: Inhibits gastric secretion and motility.

5. Growth Factors

5.1. Secretion by Non-Endocrine Tissues

Several tissues secrete growth factors.

5.2. Function

Essential for normal tissue growth and repair/regeneration.

Mechanism of Hormone Action

1. Hormone and Receptor Interaction

1.1. Hormone Receptors

Specific proteins in target tissues, either membrane-bound or intracellular.

1.2. Hormone-Receptor Complex

Formation of this complex leads to biochemical changes in the target tissue.

2. Specificity and Effects of Hormones

2.1. Specificity

Each receptor is specific to one hormone.

2.2. Regulation

Hormones regulate target tissue metabolism and physiological functions.

3. Hormone Categories

3.1. Types

(i) Peptide, polypeptide, protein hormones (e.g., insulin, glucagon).
(ii) Steroids (e.g., cortisol, testosterone).
(iii) Iodothyronines (thyroid hormones).
(iv) Amino-acid derivatives (e.g., epinephrine).

4. Modes of Hormone Action

4.1. Membrane-Bound Receptors

Generate second messengers (e.g., cyclic AMP, IP3, Ca++).

Do not enter the target cell.

4.2. Intracellular Receptors

Regulate gene expression or chromosome function.
Involve hormone-receptor complex interaction with the genome.

5. Resultant Physiological Effects

5.1. Biochemical Actions

Hormones lead to cumulative biochemical actions.

5.2. Physiological and Developmental Effects

These actions result in physiological and developmental changes.

Diagram

Summary

1. Endocrine System Overview

1.1. Function

Hormones provide chemical coordination, integration, and regulation in the body.

1.2. Composition

Includes hypothalamus, pituitary, pineal, thyroid, adrenal, pancreas, parathyroid, thymus, gonads, and additional hormone-producing organs.

2. Pituitary Gland

2.1. Structure

Divided into pars distalis, pars intermedia, and pars nervosa.

2.2. Hormone Production

Pars distalis produces six trophic hormones; pars intermedia secretes one; pars nervosa secretes two.

3. Pineal Gland

3.1. Hormone

Secretes melatonin, regulating diurnal rhythms (sleep, body temperature).

4. Thyroid Gland

4.1. Hormones and Functions

Regulates basal metabolic rate, neural development, erythropoiesis, metabolism, menstrual cycle.

4.2. Thyrocalcitonin

Decreases blood calcium levels.

5. Parathyroid Gland

5.1. Hormone

Parathyroid hormone (PTH) increases blood calcium levels, playing a role in calcium homeostasis.

6. Thymus Gland

6.1. Hormone

Secretes thymosins, essential for T-lymphocyte differentiation and humoral immunity.

7. Adrenal Gland

7.1. Composition

Composed of adrenal medulla and cortex.

7.2. Hormones

Medulla secretes epinephrine and norepinephrine; cortex secretes glucocorticoids and mineralocorticoids.

8. Pancreas

8.1. Hormones

Secretes glucagon (increases blood glucose) and insulin (decreases blood glucose).

9. Gonads

9.1. Testis

Secretes androgens, affecting male reproductive system, secondary sex characteristics, and spermatogenesis.

9.2. Ovary

Secretes estrogen and progesterone, influencing female reproductive system and pregnancy.

10. Other Hormone-Producing Organs

10.1. Heart

Secretes atrial natriuretic factor, decreasing blood pressure.

10.2. Kidney

Produces erythropoietin, stimulating erythropoiesis.

10.3. Gastrointestinal Tract

Secretes hormones like gastrin, secretin, CCK, and GIP for digestive regulation.