Zoology — Detailed Study Notes

Introduction

Zoology is the branch of biology that deals with the study of animals, including their structure, physiology, classification, evolution, genetics, ecology, development, and behaviour. Zoology plays an important role in agriculture, veterinary science, medicine, fisheries, wildlife conservation, biotechnology, and environmental science.

For TNPSC CTS, questions are generally asked from animal diversity, cell biology, genetics, physiology, evolution, ecology, developmental biology, biotechnology, immunology, parasitology, and economic zoology.

1. Animal Classification (Taxonomy)

Taxonomy is the science of identifying, naming, and classifying organisms.

Hierarchical Classification

Kingdom → Phylum → Class → Order → Family → Genus → Species

Species is the basic unit of classification.

Two Kingdom System: Plantae, Animalia

Five Kingdom System (R.H. Whittaker): Monera, Protista, Fungi, Plantae, Animalia

Three Domains (Carl Woese): Bacteria, Archaea, Eukarya

Animal Kingdom — Non-Chordates (Selected Phyla)

• Phylum Protozoa — Unicellular, microscopic; locomotion by pseudopodia, cilia or flagella. Examples: Amoeba, Paramecium, Plasmodium.
• Phylum Porifera — Simplest multicellular animals; canal system present; asymmetrical. Examples: Sycon, Spongilla.
• Phylum Cnidaria — Radial symmetry; stinging cells (cnidoblasts). Examples: Hydra, Jellyfish, Sea anemone.
• Phylum Platyhelminthes — Flatworms; bilateral symmetry; triploblastic. Examples: Tapeworm, Liver fluke.
• Phylum Nematoda — Roundworms; pseudocoelom. Examples: Ascaris, Wuchereria.
• Phylum Annelida — Segmented body; true coelom. Examples: Earthworm, Leech.
• Phylum Arthropoda — Largest animal phylum; jointed appendages; chitinous exoskeleton. Examples: Cockroach, Butterfly, Crab, Spider.
• Phylum Mollusca — Soft-bodied animals; muscular foot. Examples: Snail, Octopus, Oyster.
• Phylum Echinodermata — Marine animals; water vascular system; adults show radial symmetry. Examples: Starfish, Sea cucumber.

Chordates — Main Characteristics

Notochord, dorsal hollow nerve cord, pharyngeal gill slits, post-anal tail.

Classes:

• Pisces — Examples: Shark, Rohu.
• Amphibia — Examples: Frog, Salamander.
• Reptilia — Examples: Snake, Crocodile.
• Aves — Feathers, wings, warm-blooded. Examples: Pigeon, Peacock.
• Mammalia — Hair, mammary glands, external ears. Examples: Human, Cow, Whale, Bat.

2. Cell Biology

Cell is the structural and functional unit of life.

Cell Theory — Proposed by Schleiden and Schwann. Modified by Rudolf Virchow: "All cells arise from pre-existing cells."

Types of Cells

• Prokaryotic — No nucleus; no membrane-bound organelles.
• Eukaryotic — True nucleus; membrane-bound organelles.

Cell Organelles

• Nucleus — Controls all cellular activities.
• Mitochondria — Powerhouse of the cell; site of ATP production.
• Ribosomes — Protein synthesis.
• Endoplasmic Reticulum — Rough ER: protein synthesis; Smooth ER: lipid synthesis.
• Golgi Apparatus — Packaging and secretion.
• Lysosomes — Suicidal bags of the cell.
• Centrosome — Forms spindle fibres.

3. Biomolecules

• Carbohydrates — Immediate source of energy. Examples: Glucose, Starch, Glycogen.
• Proteins — Made of amino acids. Functions: Enzymes, hormones, body building.
• Lipids — Store energy; form cell membrane.
• Nucleic Acids — DNA (genetic material, double helix), RNA (protein synthesis). Types of RNA: mRNA, tRNA, rRNA.

4. Human Physiology

Digestive System

Main organs: Mouth, Oesophagus, Stomach, Small intestine, Large intestine.

Digestive enzymes: Salivary amylase (starch), Pepsin (protein), Trypsin (proteins), Lipase (fats).

Functions of liver: Produces bile, detoxification, glycogen storage.

Functions of pancreas: Digestive enzymes, insulin, glucagon.

Respiratory System

Organs: Nose, Trachea, Bronchi, Lungs. Functional unit: Alveolus (gas exchange). Oxygen transported by haemoglobin.

Diseases: Asthma, Tuberculosis, Pneumonia.

Circulatory System

Human heart has four chambers: Right atrium, Right ventricle, Left atrium, Left ventricle.

Blood vessels: Arteries (away from heart), Veins (towards heart), Capillaries (exchange of materials).

Blood components: Plasma, RBC (haemoglobin — oxygen transport), WBC (immunity), Platelets (blood clotting).

Blood Groups (ABO system) — Discovered by Karl Landsteiner. Universal donor: O negative. Universal recipient: AB positive.

Excretory System

Main organ: Kidney. Functional unit: Nephron. Functions: Removes nitrogenous wastes, water and salt balance. Hormone: ADH regulates water reabsorption.

Nervous & Endocrine Systems

Nervous system: CNS, PNS, ANS. Neuron is the structural and functional unit. Brain parts: Cerebrum, Cerebellum, Medulla.

Endocrine glands: Pituitary (master gland), Thyroid (thyroxine), Parathyroid (calcium regulation), Pancreas (insulin), Adrenal (adrenaline), Gonads (sex hormones).

Diseases: Diabetes mellitus (insulin deficiency), Goitre (iodine deficiency).

5. Genetics

Father of Genetics: Gregor Mendel.

Mendel's Laws: Law of Dominance, Law of Segregation, Law of Independent Assortment.

DNA double helix discovered by Watson and Crick. DNA replication is semi-conservative.

Human chromosome number: 46 (somatic), Gametes: 23 chromosomes.

Mutations: Gene mutation, Chromosomal mutation. Examples: Down Syndrome (Trisomy 21), Turner Syndrome (XO), Klinefelter Syndrome (XXY).

6. Evolution

Charles Darwin proposed the Theory of Natural Selection.

Evidence: Comparative anatomy, Embryology, Fossils, Biochemical evidence.

Adaptive radiation: Example — Darwin's finches. Speciation is the formation of new species.

7. Embryology

Fertilization: Fusion of sperm and ovum. Stages: Zygote → Cleavage → Blastula → Gastrula → Organogenesis.

Extra embryonic membranes: Amnion, Chorion, Allantois, Yolk sac. Placenta: Exchange of nutrients.

8. Animal Physiology

Muscles: Three types — Skeletal, Smooth, Cardiac. Bones: 206 bones in adult humans.

Joints: Fibrous, Cartilaginous, Synovial.

Vitamins: A (vision), B complex (metabolism), C (collagen synthesis), D (bone health), E (antioxidant), K (blood clotting).

9. Reproduction

Asexual reproduction: Binary fission, Budding, Fragmentation. Sexual reproduction: Male and female reproductive systems.

Male: Testis, Epididymis, Vas deferens. Female: Ovary, Fallopian tube, Uterus. Menstrual cycle ~28 days. Fertilization occurs in the fallopian tube.

10. Ecology

Ecology is the study of organisms and their environment. Levels: Organism, Population, Community, Ecosystem, Biome, Biosphere. Components: Biotic, Abiotic.

Food chain: Producer → Primary consumer → Secondary consumer → Tertiary consumer. Food web: Interconnected food chains.

Ecological pyramids: Number, Biomass, Energy. 10% Law proposed by Lindeman.

Biogeochemical cycles: Water, Carbon, Nitrogen, Oxygen cycles.

Ecological succession: Primary and Secondary succession. Biodiversity: Genetic, Species, Ecosystem diversity. Conservation: In-situ (National Parks, Wildlife Sanctuaries, Biosphere Reserves), Ex-situ (Zoos, Botanical Gardens, Gene Banks).

11. Environmental Biology

Pollution types: Air, Water, Soil, Noise, Radioactive. Greenhouse gases: CO2, CH4, N2O. Global warming: Increase in Earth's temperature. Ozone depletion caused by CFCs. Acid rain: SO2, NOx.

Renewable resources: Solar, Wind, Hydro, Biogas. Sustainable development: Development without affecting future generations.

12. Biotechnology

Biotechnology is the application of biological organisms for human welfare.

Recombinant DNA technology: Restriction enzymes, DNA ligase, Vectors (plasmids). PCR (Polymerase Chain Reaction) invented by Kary Mullis.

Applications: Disease diagnosis, DNA fingerprinting, Forensic science, Agriculture, Medicine. Examples: GM crops (Bt cotton, Golden Rice).

Stem cells can differentiate into various tissues. Cloning: Dolly the sheep — first cloned mammal.

13. Immunology

Types: Innate immunity, Acquired immunity. Antibodies produced by B lymphocytes.

Vaccines: Live, Killed, Subunit, mRNA vaccines. Common diseases: COVID-19, Dengue, Malaria, Tuberculosis, Typhoid, Rabies, AIDS.

14. Parasitology

Parasite: Lives on or in another organism. Endoparasites: Tapeworm, Roundworm. Ectoparasites: Lice, Ticks.

Life cycles: Plasmodium (vector: female Anopheles mosquito), Wuchereria (vector: Culex mosquito), Trypanosoma (vector: Tsetse fly).

15. Economic Zoology

Sericulture (silk production) — silkworm: Bombyx mori. Apiculture (bee keeping) — products: Honey, Wax; role in pollination. Pisciculture — fish farming (major carps: Catla, Rohu, Mrigal). Poultry (layers, broilers). Dairy — milk production. Vermiculture — earthworm culture. Lac culture — lac insect produces shellac.

16. Wildlife Biology

Protected areas: National Parks, Wildlife Sanctuaries, Biosphere Reserves. Important projects: Project Tiger (1973), Project Elephant (1992).

IUCN categories: Least Concern, Near Threatened, Vulnerable, Endangered, Critically Endangered, Extinct in the Wild, Extinct.

17. Animal Behaviour (Ethology)

Types: Instinct, Learning, Conditioning, Migration, Hibernation. Communication: Pheromones, Bird songs, Honey bee dance.

Social behaviour: Ants, Termites, Honey bees, Primates.

Important scientists: Aristotle (father of zoology), Carolus Linnaeus (taxonomy), Charles Darwin (evolution), Gregor Mendel (genetics), Watson & Crick (DNA), Rudolf Virchow (cell theory), Karl Landsteiner (blood groups), Kary Mullis (PCR), Louis Pasteur (vaccination), Edward Jenner (smallpox vaccine), Robert Koch (germ theory), Antonie van Leeuwenhoek (microbiology).

Frequently Asked TNPSC CTS Zoology Facts

• Largest animal phylum — Arthropoda
• Largest mammal — Blue Whale
• Largest bird — Ostrich
• Smallest bird — Bee Hummingbird
• Fastest land animal — Cheetah
• Largest fish — Whale Shark
• Largest reptile — Saltwater Crocodile
• National Aquatic Animal of India — Ganges River Dolphin
• National Bird of India — Indian Peacock
• Functional unit of kidney — Nephron
• Functional unit of nervous system — Neuron
• Functional unit of lung — Alveolus
• Powerhouse of cell — Mitochondria
• Protein synthesis — Ribosome
• Universal donor — O Negative
• Universal recipient — AB Positive
• Human chromosome number — 46
• Adult human bones — 206
• Normal body temperature — 37°C
• Normal blood pH — 7.35–7.45
• Heart chambers — Four
• Largest gland — Liver
• Largest endocrine gland — Thyroid
• Master gland — Pituitary
• Insulin deficiency causes — Diabetes Mellitus
• Iodine deficiency causes — Goitre
• Vitamin C deficiency — Scurvy
• Vitamin D deficiency — Rickets
• Vitamin A deficiency — Night Blindness
• Vitamin K deficiency — Delayed blood clotting
• DNA replication — Semi-conservative
• First cloned mammal — Dolly
• Father of Zoology — Aristotle
• Father of Genetics — Gregor Mendel
• Theory of Natural Selection — Charles Darwin