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Rahul Devashish
Rahul DevashishCourseScienceBiology
4 Sept 2025·26 min read·

Biology

Origin of Earth & Life

  • Earth formed about 4.5–4.6 billion years ago from solar nebulae (Accretion Theory).
  • Primitive atmosphere: methane (CH₄), ammonia (NH₃), hydrogen (H₂), carbon dioxide (CO₂), water vapour — no free oxygen.
  • First life appeared around 3.5–4.0 billion years ago in water as simple nucleoprotein particles.
  • Cyanobacteria (blue-green algae) considered the oldest life forms.
  • Great Oxygenation Event (~2.4 bya) → oxygen accumulation due to photosynthesis by cyanobacteria.

Theories of Origin of Life

  • Oparin–Haldane Theory: Life originated by chemical evolution of organic molecules in the primitive atmosphere.
    • J.B.S. Haldane (1929) → “Primordial soup” concept.
    • A.I. Oparin (1924) → book The Origin of Life.
  • Miller–Urey Experiment (1953):
    • Mixture of CH₄, NH₃, H₂, H₂O exposed to electric sparks.
    • Produced amino acids (glycine, alanine).
    • First experimental proof of abiotic synthesis.

Theories of Evolution

  • Lamarckism (Jean Baptiste Lamarck, 1801): Theory of inheritance of acquired characters.
    • Example: giraffe’s long neck due to stretching, webbed feet in aquatic birds.
    • Book: Philosophie Zoologique (1809).
  • Darwinism (Charles Darwin, 1859): Book On the Origin of Species.
    • Variation among individuals, Overproduction of offspring, Struggle for existence, Survival of the fittest, Inheritance of useful variations.
  • Mutation Theory (Hugo de Vries, 1901):
    • Studied Oenothera lamarckiana (evening primrose).
    • Evolution occurs by sudden mutations, some useful, some harmful.
  • Neo-Darwinism (Modern Synthesis): Combination of Darwin’s theory + Mendel’s genetics + modern discoveries.
    • Factors: mutation, recombination, natural selection, isolation, heredity.
    • Contributors: Dobzhansky, Fisher, Haldane, Wright, Mayr, Stebbins.

Evidence of Evolution

  • Morphological evidence:
    • Homologous organs → same origin, different functions (e.g., forelimbs of human, whale, bat, horse).
    • Analogous organs → different origin, similar functions (e.g., wings of bat & insect).
  • Embryological evidence: similarity in early embryos of vertebrates.
  • Paleontological evidence: fossil records show gradual development.
  • Biochemical evidence: similar DNA, RNA, proteins among species.

Important Fossils & Human Evolution

  • Archaeopteryx (Jurassic period, 150 mya): Connecting link between reptiles & birds.
  • Dinosaurs: dominated Mesozoic era (Age of Reptiles, 252–66 mya).
  • Mammoth: extinct ancestor of modern elephant.
  • Human Evolution:
    • Australopithecus (~4 mya, Africa).
    • Homo habilis (~2.4 mya, first tool user).
    • Homo erectus (~1.5 mya, first to use fire).
    • Neanderthal man (~100k years ago, Europe).
    • Cro-Magnon man (~40k years ago, brain 1600 cc) ancestor of modern humans.
    • Homo sapiens → modern human, brain 1400–1500 cc.

Taxonomy & Classification

Introduction to Taxonomy

  • Taxonomy: Science of identification, nomenclature, and classification of organisms.
  • Systematics: broader branch including taxonomy + evolutionary relationships.
  • Father of Biology: Aristotle.
  • Father of Botany: Theophrastus.
  • Father of Taxonomy: Carl Linnaeus (1707–1778).
  • Father of Medicine: Hippocrates (Essay on Human Disease).
  • Binomial Nomenclature:
    • Uses two names → Genus + Species.
    • Names in Latin, italicized.
    • Example: Homo sapiens (human), Felis catus (cat).
    • Other examples: Felis (Cat), Bos (Cow), Triticum (Wheat), Oryza (Rice), Mangifera (Mango), Cicer (Gram), Canis (Dog), Pisum (Pea), Brassica (Mustard), Musca (Housefly).

Classification Systems

  • Two-kingdom system (Linnaeus, 1758): Plantae & Animalia.
  • Three-kingdom system (Haeckel, 1866): Protista added.
  • Four-kingdom system (Copeland, 1956): Monera, Protista, Plantae, Animalia.
  • Five-kingdom system (Whittaker, 1969) (most accepted): Monera, Protista, Fungi, Plantae, Animalia.
    • Basis of Whittaker’s classification:
      • Cell type (prokaryote/eukaryote), Body organization (unicellular/multicellular), Nutrition (autotrophic/heterotrophic), Reproduction (sexual/asexual – not primary), Phylogeny (evolutionary history).

Cell & Cytology

Discovery & Cell Theory

  • Cell discovered by Robert Hooke (1665) in cork.
  • Anton van Leeuwenhoek (1674) observed first living cells.
  • Purkinje → discovered protoplasm.
  • Cell theory (1838–39): proposed by Schleiden (plants) & Schwann (animals).
    • All living organisms are made of cells.
    • Cell is the basic structural & functional unit.
  • Rudolf Virchow (1855) modified theory → “Omnis cellula e cellula” (all cells come from pre-existing cells).

Cell Types

  • Prokaryotic cells (Monera):
    • No true nucleus (nucleoid).
    • No membrane-bound organelles.
    • Example: bacteria, cyanobacteria, archaea.
  • Eukaryotic cells (Protista, Fungi, Plantae, Animalia):
    • Well-defined nucleus with nuclear membrane.
    • Membrane-bound organelles present.
    • Example: plant & animal cells.

Cell Facts

  • Smallest cell → Mycoplasma gallisepticum.
  • Largest cell → Ostrich egg.
  • Longest cell → Neuron.
  • Plant cell → trilayered cell wall (cellulose), no lysosome.
  • Animal cell → lysosome present.
  • Humans cannot digest cellulose.

Cell Organelles

  • Nucleus: discovered by Robert Brown; contains DNA & nucleolus.
  • Mitochondria: “Powerhouse of the cell”; site of respiration; semi-autonomous.
  • Endoplasmic Reticulum (ER):
    • Rough ER → protein synthesis.
    • Smooth ER → lipid synthesis, detoxification.
  • Golgi Apparatus: protein modification, secretion, packaging.
  • Ribosomes: site of protein synthesis; 70S (prokaryotes), 80S (eukaryotes).
  • Lysosomes: digestive enzymes, “suicidal bags”; found in animals.
  • Plastids: leucoplast, chromoplast, chloroplast.
  • Vacuoles: maintain turgidity.
  • Centrosome: only in animal cells; helps in cell division.

Cell Division

  • Amitosis: in unicellular organisms (bacteria, protozoa).
  • Mitosis: Somatic cell division → 2 diploid cells.
  • Meiosis: Gamete formation → 4 haploid gametes, genetic variation.

DNA & RNA

DNA

  • Discovered by Friedrich Miescher (1869).
  • Double helix model by Watson & Crick (1953), based on Rosalind Franklin’s X-ray diffraction.
  • Chargaff’s rule: A=T, G≡C.
  • Found in nucleus, mitochondria, chloroplast.

RNA

  • Single-stranded (double in some viruses).
  • Bases: A, U, G, C.
  • Types: mRNA, tRNA, rRNA.
  • Functions: protein synthesis, genetic information carrier.

Molecular Genetics

  • Central Dogma (Crick, 1958): DNA → RNA → Protein.
  • DNA as genetic material proved by:
    • Avery, MacLeod, McCarty (1944).
    • Hershey–Chase experiment (1952).
  • Mutations: heritable DNA changes (point, chromosomal, genome).
  • Jumping Genes (Transposons): discovered by Barbara McClintock (Nobel 1983).

Mendelian Genetics

  • Gregor Mendel (1865) = Father of Genetics.
  • Experiments on pea plant (Pisum sativum).
  • Laws: Dominance, Segregation, Independent Assortment.
  • Chromosome theory of inheritance → Sutton & Boveri.
  • Morgan (1910): discovered linkage in Drosophila.

Genetic Disorders

  • Chromosomal: Down Syndrome (Trisomy 21), Turner’s Syndrome (XO), Klinefelter’s (XXY).
  • Mendelian: Haemophilia, Colour Blindness, Sickle Cell Anaemia.
  • Multifactorial: Diabetes, Hypertension.

Plant Physiology

Photosynthesis

  • Fundamental process in chloroplasts.
  • Light reaction (thylakoid), Dark reaction (stroma).
  • Equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.

Respiration in Plants

  • Aerobic → 36 ATP.
  • Anaerobic → 2 ATP + alcohol/lactic acid.

Plant Hormones

  • Auxins, Gibberellins, Cytokinins, Abscisic Acid, Ethylene.

Plant Kingdom

  • Thallophyta, Bryophyta, Pteridophyta, Gymnosperms, Angiosperms.
  • Fertilisation → seed, fruit.
  • Plant tissues: meristematic, permanent (simple, complex).
  • Economic botany: food parts, fibres, medicinal plants.

Monera

  • Prokaryotic, unicellular organisms.
  • Includes bacteria, cyanobacteria, mycoplasma, archaebacteria.
  • Bacteria discovered by Leeuwenhoek.
  • Diseases: TB, Leprosy, Diphtheria, Pneumonia, Cholera, Typhoid, Tetanus, etc.
  • Archaebacteria: Methanogens, Halophiles, Thermoacidophiles.

Animal Kingdom

  • Protozoa → unicellular.
  • Porifera → sponges.
  • Cnidaria → Hydra, jellyfish.
  • Platyhelminthes → flatworms.
  • Nematoda → roundworms.
  • Annelida → earthworm, leech.
  • Arthropoda → insects, crabs, spiders.
  • Mollusca → octopus, snail.
  • Echinodermata → starfish, sea urchin.
  • Chordata → fishes, amphibians, reptiles, birds, mammals.

Other Important Points

Excretory & Useful Products

  • Alkaloids: Quinine, Reserpine.
  • Latex: rubber plants.
  • Opium: alkaloids (morphine, codeine).

Metabolism

  • Anabolism (synthesis), Catabolism (breakdown).

Special Plant & Animal Facts

  • Insects → 6 legs.
  • Mosquito → female sucks blood.
  • Firefly → enzyme luciferase.
  • False fishes: jellyfish, starfish, silverfish.
  • King Cobra → longest venomous snake.
  • River Dolphin → India’s national aquatic animal.

Historical Discoveries & Fathers

  • Aristotle → Biology.
  • Theophrastus → Botany.
  • Hippocrates → Medicine.
  • Carl Linnaeus → Taxonomy.
  • Leeuwenhoek → Bacteriology.
  • Louis Pasteur → Germ theory, Pasteurisation.
  • Robert Koch → Anthrax & TB.
  • Alexander Fleming (1928) → Penicillin.
  • Gregor Mendel → Genetics.

#Human Physiology

Digestive System

  • Starts from the buccal cavity and ends at the small intestine.
  • Starch into maltose through Ptyalin.
  • Amylase converts starch into soluble sugar.
  • Lipase converts fats into glycerine and fatty acid.
  • Lysosomes destroy bacteria.
  • Chyme: food material.
  • Humans are diphyodont (2 sets of teeth).
  • Thecodont: trapped in jaw.
  • Milk teeth: 20 teeth of childhood.
  • Dental formula: Incissor 2/2, Canine 1/1, Premolar 2/2, Molar 3/3 = 32 teeth (Heterodont).
  • Enamel: hardest part of body (calcium phosphate + carbonate); shining, uppermost part.
  • Tongue: Taste villi → Sweetness (front), Bitter (near larynx), Sour (sides), Salty (middle).
  • Digestive tract length: 5–9m.
  • Gastric/digestive juices: HCL, Renin, Pepsin.
  • Caecum and vermiform appendix are residual organs.
  • Trypsin in small intestine converts proteins and peptons into polypeptides and amino acids.
  • Large intestine absorbs water from chyme.

Digestive Glands

  • Salivary glands → Secrete saliva (ptyalin/amylase).
  • Liver → Largest gland (1.5–2 kg).
    • Secretes bile.
    • Converts glucose to glycogen (storage), controlling blood sugar.
    • Detoxifies blood.
    • Hormone regulation.
    • Cholesterol management.
    • Storage: glycogen, vitamins (A, D, E, K, B12), minerals (iron, copper).
    • Removes old red blood cells and pathogens via Kupffer cells.
    • Synthesizes fibrinogen protein.
    • Excess amino acids → ammonia and pyruvic acids.
    • Ammonia transformed to urea.
  • Pancreas → Mixed/dual gland.
    • Exocrine → Enzymes (trypsin, amylase, lipase).
    • Endocrine → Hormones: Glucan, Insulin & Somatostatin (GIS) from α, β, γ cells of Islets of Langerhans.
    • Secretion pH: ~8–9 (alkaline, neutralizes stomach acid).
    • Duct: Main pancreatic duct joins bile duct to duodenum.
  • Gallbladder → Stores bile.

Circulatory System

  • Double circulatory system (by William Harvey).
  • Heart: muscular organ, ~250–300 g.
    • Beats 72–75 times per minute.
    • 4 chambers: RA, RV, LA, LV.
    • Valves: bicuspid (left), tricuspid (right) → prevent reverse blood flow.

Blood Circulation

  • By coronary artery.
  • Pulmonary: heart ↔ lungs.
  • Systemic: heart ↔ body.

Arteries

  • Carry oxygenated blood (except pulmonary artery).
  • Red, no valves, located deep.
  • Thicker & muscular wall, narrow cavity.

Veins

  • Carry deoxygenated blood (except pulmonary veins).

  • Violet, valves present, upper layer, flattened cavity.

  • Hepatic portal vein: intestine → liver.

  • Pulse rate: high in fever & babies, low during sleep.

  • Blood pressure: Normal = 120/80 mmHg.

    • Measured by sphygmomanometer.
    • Hypertension: >140/100.
    • Hypotension: below normal.

  • Pacemaker: group of tissues for heartbeat; recorded via electrocardiograph.

  • Control of heartbeat: Thyroxine, adrenaline, medulla oblongata.

  • Haemoglobin: Violet (Oxyhaemoglobin → Red).

  • Insulin: regulates blood sugar (deficiency → Diabetes).

Lymph

  • Fluid, clots like blood.
  • Formed at lymph nodes.
  • Forms lymphocytes.
  • Helps diffusion, maintains osmotic pressure.

Blood Composition

  • Fluid connective tissue; maintains uniform temperature & pressure.
  • Total blood volume: 5–6 litres.
  • pH: 7.35–7.45.
  • Viscous fluid (thicker than water).
  • 45% cells (RBCs, WBCs, platelets), ~55% plasma.
  • Temp: ~37°C (98.6°F).

Plasma

  • ~55% of blood; 90–92% water; contains proteins, salts.
  • Proteins: Albumin (osmotic pressure), Globulins (immune), Fibrinogen (clotting).
  • Yellowish fluid matrix.
  • Salts: Sodium chloride, sodium carbonate.

RBCs (Erythrocytes)

  • 90% of blood cells, no nucleus (except camels).
  • Life span: ~120 days.
  • Biconcave; contain haemoglobin.
  • Formed in bone marrow; destroyed in spleen ("graveyard of RBCs").
  • Function: O₂ from lungs to tissues; CO₂ back to lungs.
  • Stimulated by Vitamin B12 and folic acid.
  • Needed more at higher altitudes.

WBCs (Leukocytes)

  • Defend against infections, regulate immunity.
  • Nucleated; no haemoglobin.

Types

  • Granulocytes:

    • Neutrophils → most abundant, destroy bacteria.
    • Eosinophils → anti-allergy.
    • Basophils.

  • Agranulocytes:

    • Lymphocytes → form antibodies.
    • Monocytes → phagocytosis.

  • Count: 4,000–11,000/µL.

  • Produced in bone marrow, lymph nodes, liver, spleen.

  • Lifespan: hours to years (memory lymphocytes persist).

  • Function: Destroy pathogens, antibodies, debris removal.

Platelets (Thrombocytes)

  • Lifespan: 7–10 days; removed by spleen/liver.
  • Count: 150,000–450,000/µL.
  • Help in clotting (fibrinogen, prothrombin).
  • Sodium & potassium oxalate → speed clotting.
  • Prevent blood loss; heal wounds.
  • Dysfunction → thrombosis/bleeding.
  • Vitamin K aids clotting.
  • Serum = residual yellowish fluid.
  • Heparin = anticoagulant.

Blood Groups

  • Discovered by Carl Landsteiner.
  • Antigen → RBC; Antibody → Plasma.
  • Rh factor discovered by Landsteiner & Weiner (from Rhesus monkey).
  • Erythroblastosis foetalis: Rh– mother, Rh+ child (affects 2nd child; cure available).

Parents → Offspring Blood Groups

  • O × O → O
  • O × A → O, A
  • O × B → O, B
  • O × AB → A, B
  • A × A → A, O
  • B × B → B, O
  • A × AB → A, B, AB
  • B × AB → A, B, AB
  • AB × AB → A, B, AB
  • A × B → A, B, AB, O

Endocrine System

Hormones

● Chemical messengers that regulate metabolism, sexual function, homeostasis, heart rate, tissue & body repair etc

Pheromones

● Chemicals secreted by organism, elicit social response in same species.
● Functions – Marking territory, Promote bonding, alarm others, influence menstrual cycle.
● Through fluids like sweat, urine etc.
● Examples – Ants, Elephants.

Endocrine Glands

● Ductless glands.
● Release directly into blood, reach target organs.
● Examples – Pituitary, Thyroid, Parathyroid, Adrenals.

Exocrine Glands

● With ducts.
● Products – Enzymes, mucous, other substances.
● Examples – Salivary glands, Sweat glands.

Mixed Gland - Pancreas.

Hypothalamus

● Called Master of Master gland.
● Location above pituitary.
● Gonadotropin releasing hormone: stimulates the release of follicle stimulating hormone and LH from Pituitary; regulates reproductive functions.
● Corticitropin-releasing hormone - stress
● Growth-hormone releasing hormone
● Somatostatin - inhibits Growth hormone & TSH release.
● Dopamine - inhibits prolactin; influences motivation, reward, memory.
● Oxytocin – formed in the hypothalamus but stored & released by pituitary; “Love hormone” or binding hormone.
● Vasopressin – formed in the hypothalamus but stored & released by pituitary; helps water reabsorption from kidney.

Pituitary Gland

● Location – Anterior brain.
● Size – Pea-sized.
● Called Master gland.
● Secretes –

  • Prolactin (Milk production, reproductive health)
  • Adrenocorticotropic (Cortisol production in adrenals; stress & immune response)
  • Somatotropin (Growth)
  • Melanocytes (skin pigmentation, appetite)
  • Thyroid stimulating hormone (thyroid hormone, metabolism)
  • Follicle stimulating hormone (Eggs & sperm)
  • Luteinising hormone (Ovulation & estrogen/progesterone in females, Testosterone in male)
  • Antidiuretic Hormone/ADH/Vasopressin (urine production, water balance, BP)
  • Oxytocin (Child birth, social bonding)

Pineal Gland

● Called Third eye; Smallest gland; Located in brain.
● Secretes Melatonin, regulates circadian rhythm & light/dark cycle.

Thyroid Gland

● Shape Butterfly.
● Thyroxine & Triiodothyronine (Temperature regulation, metabolism, brain development)
● Calcitonin (Regulates calcium & phosphate in blood- lowers blood calcium level).

Parathyroid/Parathormone Gland

● Location behind neck.
● Independent of pituitary.
● Secretes Parathormone, raises blood calcium level; regulates bone remodelling and kidney function.

Thymus Gland

● Location base of neck.
● Active till puberty.
● Helps in maturation of T-lymphocyte cells (Immunity).

Adrenal Gland

● Atop kidney

Cortex Hormones

  • Cortisol (Glucocorticoid) - blood sugar, inflammation
  • Aldosterone (Mineralocorticoid) - sodium and potassium balance, BP.
  • Androgen - Precursor to sex hormone; contributes to male trait.

Medulla Hormones

  • Epinephrine (Adrenaline) - increases heart rate and energy during fight or flight = fight or flight hormone.
  • Norepinephrine (Noradrenaline) - constrict blood vessels supports alertness and stress response.

Ovaries

● Inhibin: inhibits follicle stimulating hormone; fine tunes reproductive cycle.
● Estrogen – From ovarian follicles, helps breast development, vaginal maturation (female secondary characters), bone health.
● Progesterone – From corpus luteum (ruptured follicle), prepares uterus lining for foetus retention during pregnancy.

Testes

● Secretes Androgen (by Leydig cells).
● Inhibin - inhibits follicle stimulating hormone; regulates sperm production
● Androgen determines male characters – deep voice, beard.
● Testosterone - Major androgen; Develops male secondary traits; supports sperm production and muscle growth.

Pancreas

● Both endocrine & exocrine.
● Insulin - lowers blood sugar by promoting Glucose uptick in cells; regulates fat and protein metabolism; zinc stabiliser. Deficiency causes Diabetes mellitus. Roots of Dahaliya tree used for diabetes treatment.
● Produced by beta cells of islets of Langerhans.
● Glucagon - Raises blood sugar by stimulating glycogen breakdown; counters insulin.
● Somatostatin: inhibits insulin and glucagon; regulates digestion.

Other Non-primary endocrine organs

● Kidney: Erythropoietin - stimulates RBC production; responds to low oxygen.
● Heart: Arterial Natriuretic Peptide - Lowers BP, promotes sodium excretion.
● Liver: Insulin-like Growth Factor - promotes tissue growth

Ecology & Environment

Structure of Ecosystem

  1. Producers (autotrophs): green plants, algae.
  2. Consumers (heterotrophs):
    • Primary (herbivores).
    • Secondary (carnivores).
    • Tertiary (top carnivores).
  3. Decomposers: fungi, bacteria (break down organic matter).

Energy Flow

● Solar energy → captured by producers → transferred to consumers.
● Follows 10% Law (Lindeman’s Law): only 10% energy passes from one trophic level to the next.
● Unidirectional flow.

Food Chains & Webs

● Food Chain: linear transfer of energy. (e.g., Grass → Deer → Lion).
● Food Web: interconnected food chains, ensures stability of the ecosystem.

Biogeochemical Cycles

● Water cycle: evaporation → condensation → precipitation.
● Carbon cycle: CO₂ fixed by plants → consumed by animals → returned by respiration & decay.
● Nitrogen cycle: nitrogen fixation (Rhizobium, lightning), nitrification, denitrification.
● Oxygen cycle: O₂ produced in photosynthesis, consumed in respiration.

Biodiversity & Environment

In-situ Conservation (within natural habitat): National Parks, Sanctuaries, Biosphere Reserves.
Ex-situ Conservation (outside natural habitat): Zoos, Botanical gardens, Seed banks, Cryopreservation.

Global Warming & Greenhouse Effect

Caused by accumulation of greenhouse gases: CO₂, CH₄, N₂O, CFCs.
Effects: rising temperature, melting glaciers, sea-level rise, extreme weather.

Ozone Depletion

Ozone layer absorbs harmful UV radiation. CFCs (chlorofluorocarbons) destroy ozone.
Causes skin cancer, cataracts, ecological damage.
Montreal Protocol (1987) signed to ban CFCs.

Acid Rain

Caused by SO₂ + NOx combining with water.
Damages crops, soil, aquatic life, buildings (Taj Mahal corrosion).

Eutrophication

Excess nutrients (nitrates, phosphates) in water bodies.
Leads to algal bloom, oxygen depletion, fish death.

Environmental Movements

● Chipko Movement (1973, Chamoli, Uttarakhand) → Sundar Lal Bahuguna, Chandi Prasad Bhatt, Gaura Devi
● Apikko Movement (1983, in Uttara Kannada, Karnataka) on lines of Chipko Movement, Pandurang Hegde.
● Silent Valley Movement (Kerala, 1978) → to save tropical rainforest.
● Narmada Bachao Andolan → Medha Patekar

Excretory System

  • Kidneys: paired, bean-shaped; lower back.
    • Filter ~180 L/day blood; produce 1–2 L urine.
    • Regulate water, electrolytes, pH.
    • Cortex (outer), Medulla (inner).
  • Nephrons (~1 million/kidney):
    • Glomerulus → filters blood.
    • Bowman’s capsule → collects filtrate.
    • Tubules → reabsorb water, nutrients.
  • Dialysis = selective filtration.
  • Urine: 95% water, 2% urea + fats, glucose, uric acid; yellow due to urochrome; acidic; denser than water.
  • Hormones: ADH (water retention), Aldosterone (Na⁺ balance).
  • Other excretory organs: lungs, skin (sweat, oil), liver, spleen, intestine.
  • Tears (lacrimal gland) → alkaline.

Nervous System

  • CNS: Brain + spinal cord → voluntary & involuntary control.
  • PNS: Cranial & spinal nerves, ganglia, motor/sensory pathways.
  • Cranium: hollow bones.
  • Neuron: structural & functional unit; longest cell.
  • Synapse: junction; neurotransmitters (e.g., acetylcholine) transmit signals.

Brain

  • Cerebrum: Largest part; intelligence, memory, language, sensory, voluntary.
  • Cerebellum: Balance, posture.
  • Medulla oblongata: Involuntary (breathing, heartbeat, CO₂/pH control).

Other Functions

  • Reflex action: spinal cord (involuntary).
  • Sensory/Afferent → receptors → brain/spinal cord.
  • Motor/Efferent → brain/spinal cord → effectors.
  • Thalamus: Pain, hot, cold sensation.
  • Hypothalamus: Hormone control (pituitary), hunger, thirst, emotions, temp, BP, sweat.
  • Sympathetic NS: ↑ sugar, BP, respiration, RBC; vasoconstriction; ↓ saliva.
  • Parasympathetic NS: Opposite.
  • Ear: balance.
  • Cochlea: hearing.

Skeletal System

  • Human body: 206 bones (adult); 300 in childhood.
  • Skull: 28 bones.
  • Vertebral column: 26 vertebrae.
  • Ribs: 12 pairs.
  • Handlimbs: 60 bones; Forelimbs: 60 bones.
  • Endoskeleton: bone, connective tissue (Ca, Mg).
  • Exoskeleton: scales (fishes), shell (tortoise), feathers (birds), hairs (mammals).
  • Red bone marrow → RBC; Yellow → WBC.
  • Largest/strongest bone: Femur.
  • Smallest bone: Stapes (ear).
  • Ligament: bone ↔ bone.
  • Tendon: muscle ↔ bone.
  • Bone = rigid; Cartilage = elastic.
  • Minerals: Ca, P for bone strength.

Important Bones

  • Sternum: breastbone.
  • Clavicle: collarbone.
  • Patella: kneecap.
  • Scapula: shoulder blade.
  • Humerus: upper arm.
  • Radius & Ulna: forearm.
  • Tibia & Fibula: lower leg.
  • Pelvis: hip bone.

Muscular System

  • Muscle fibers: elongated, contractile cells.
  • Strongest muscle (lifting capacity): Masseter (jaw).
  • Muscle types: skeletal (voluntary), smooth (involuntary), cardiac (heart).
  • Functions: movement, circulation, digestion, heat production.

Respiratory System

  • ATP = universal energy currency.
  • Krebs cycle in mitochondria → max ATP.
  • Lungs covered by pleural membranes.
  • O₂ transport → haemoglobin.
  • CO poisoning → carboxyhaemoglobin (toxic).
  • Respiration = gas exchange.
  • Ventilation = breathing.

Structures & Functions

  • Alveoli: gas exchange via diffusion.
  • Diaphragm: aids breathing.
  • Trachea: windpipe, cartilage rings.
  • Bronchi/Bronchioles: distribute air.
  • Larynx: voice box.
  • Epiglottis: covers larynx while swallowing.
  • Nasal cavity: filters, warms, moistens air.
  • Pharynx: air/food passage.
  • Lungs: Right (3 lobes), Left (2 lobes, smaller).
  • Intercostal muscles: help ventilation.

Breathing

  • Inhalation: diaphragm contracts, air in.
  • Exhalation: diaphragm relaxes, air out.
  • Transport: O₂ binds Hb; CO₂ → bicarbonate/dissolved.
  • Medulla oblongata: controls rate (based on CO₂).
  • Chemoreceptors: detect pH, CO₂, O₂.

Other Receptors

  • Olfactory: nose (weak in humans, strong in dogs/cats).
  • Photoreceptor: eyes.

Importance

  • Supplies O₂, removes CO₂, maintains pH, supports metabolism.
  • Special forms:
    • Fish, prawns → gills.
    • Lizards, birds → pulmonary + skin.
    • Grasshopper, cockroach → trachea.

Reproductive System

Male

  • Testes: sperm + testosterone.
  • Epididymis: sperm storage, maturation.
  • Vas deferens: transports sperm.
  • Prostate gland: alkaline fluid, nourishes sperm.
  • Sperm: male gametes, motile, genetic material.
  • Testosterone: regulates sperm, secondary sex traits.
  • Cowper’s gland: neutralizes urine, lubricates urethra.

Female

  • Ovaries: ova + hormones (estrogen, progesterone).
  • Fallopian tubes: transport ova; fertilization site (internal fertilization).
  • Uterus: muscular; supports pregnancy.
  • Endometrium: thickens for implantation, sheds during menstruation.
  • Vagina: birth canal; receives sperm.
  • Ovum: female gamete; non-motile.
  • Hormones (estrogen/progesterone): regulate cycle, pregnancy, secondary traits.
  • Menstruation: monthly shedding.
  • Ovulation: mature ovum release (~day 14).
  • Nourishment: via chorion, amnion, placenta.

Microbiology

Bacteria

  • Unicellular prokaryotes without true nucleus
  • Discovered by Anton van Leeuwenhoek
  • Shapes:
    • Cocci → spherical
    • Bacilli → rod-shaped
    • Spirilla → spiral
    • Vibrios → comma-shaped
  • Reproduction:
    • Asexual (binary fission)
    • Conjugation (Horizontal gene transfer)
  • Nutrition:
    • Autotrophic → photosynthetic, chemosynthetic
    • Heterotrophic → saprophytes, parasites
  • Useful roles:
    • Decomposition of organic matter
    • Fermentation (lactic acid, alcohol)
    • Antibiotic production (Streptomyces → streptomycin)
    • Nitrogen fixation (free-living & symbiotic)

Archaebacteria

  • Ancient bacteria with unique cell walls (no peptidoglycan); some (like methanogens) lack cell walls
  • Found in extreme environments:
    • Methanogens → anaerobic, produce methane (found in cattle rumen)
    • Halophiles → survive in high salt (salt pans)
    • Thermoacidophiles → survive in hot springs, acidic environments

Mycoplasma

  • Smallest living cell
  • Lack a cell wall → resistant to antibiotics that target cell wall
  • Can be parasitic or free-living in plants, animals

Cyanobacteria (Blue-Green Algae)

  • Prokaryotic, photosynthetic, autotrophic
  • Can fix atmospheric nitrogen (heterocysts)
  • Examples: Nostoc, Anabaena, Oscillatoria
  • Importance:
    • Primary producers in aquatic systems
    • Used as biofertilizers in paddy fields (esp. Anabaena)
    • Responsible for adding O₂ to the atmosphere

Viruses

  • Discovered by Dmitri Ivanovsky (1892) in tobacco mosaic disease; further characterized by Martinus Beijerinck
  • Non-cellular, acellular infectious agents
  • Composed of nucleic acid (DNA or RNA) + protein coat (capsid)
  • Non-living outside host; living inside host cell
  • Term “virus” by Beijerinck (1898)
  • TMV (Tobacco Mosaic Virus) first identified; crystallized by W.M. Stanley (1935)
  • Acellular structure; obligate intracellular parasites
  • Studied under Virology
  • Show properties of both living & non-living

Fungi

  • Eukaryotic, heterotrophic
  • Fungal cell walls composed of chitin + polysaccharides (glucans, mannans)
  • Can be unicellular (yeast) or multicellular (mushrooms, molds)
  • Examples & uses:
    • Yeast → fermentation (alcohol, bread); reproduces by budding
    • Mushrooms → edible (Agaricus), poisonous (Amanita); multicellular, spore-producing
    • Mold → multicellular, filamentous
  • Other features:
    • Store food as glycogen
    • Study of fungi = Mycology
    • Lichen → symbiotic association of fungus + algae/cyanobacteria
      • Fungi absorb water & minerals
      • Algae prepare food
      • Lichens = bioindicators of air pollution
      • Study = Lichenology
    • Mycorrhiza → fungus + plant root (mutualistic)
  • Applications:
    • Yeast → anaerobic respiration (fermentation) in wine, vinegar, beer
    • Alexander Fleming (1928) → discovered Penicillin (from Penicillium notatum) – first antibiotic

Protozoa

  • Unicellular eukaryotes
  • Examples:
    • Amoeba → free-living
    • Paramecium → ciliated
    • Plasmodium → causes malaria
    • Trypanosoma → sleeping sickness
    • Leishmania → kala-azar

Nutrition

Carbohydrates

  • Main source of energy.
  • Composed of C, H, O (1 : 2 : 1)
  • Energy value: 4 kcal/g.
  • Provide 55–75% of total calories.
  • Monosaccharides – Glucose, Galactose, Fructose
  • Disaccharides – Sucrose, Maltose, Lactose
  • Polysaccharides – Starch, Cellulose, Chitin, Glycogen, extracted from plants, insoluble in water.
  • Glucose – Instant energy; Grapes
  • Stored as glycogen in liver & muscles.

Proteins

  • Building blocks of body (“Body’s structural material”).
  • Composed of amino acids (20 total, 9 essential for humans – Arginine is sometimes considered 10th essential amino acid).
  • Energy value: 4 kcal/g.
  • Functions:
    • Growth and repair of tissues
    • Enzymes & hormones are proteins
    • Form hemoglobin, antibodies, structural proteins
    • Contractile protein for contractile muscle
    • Antibody is a defensive protein
    • Instant energy in emergency
    • Biocatalyst
    • Hormones are proteins
  • Daily requirement:
    • Adults: ~45 g/day (women), ~55 g/day (men)
    • Pregnant & lactating women: ~65 g/day
  • Deficiency diseases:
    • Kwashiorkor → swollen belly, oedema, thin limbs
    • Marasmus → severe wasting, muscle loss, weakness

Fats (Lipids)

  • Secondary energy source, stored form of energy.
  • Made of glycerol + fatty acids + carbon + hydrogen + oxygen (less oxygen than carbs).
  • Insoluble in water; soluble in organic solvents like chloroform, benzene.
  • Energy value: 9 kcal/g (most concentrated source).
  • Body fat ~7% of total weight.
  • Types of fats:
    • Saturated fats (animal fats, butter, ghee) → increase cholesterol.
    • Unsaturated fats (vegetable oils, fish oils, nuts) → lower cholesterol.
  • Essential fatty acids: Linoleic acid (ω-6), α-Linolenic acid (ω-3).
  • Functions:
    • Provide energy during starvation
    • Protect internal organs
    • Help in absorption of fat-soluble vitamins (A, D, E, K)

Water & Minerals

  • Water: 50–65% in adults and higher in infants.
    • Functions: solvent, transport medium, regulates temperature, excretion.
  • Minerals:
    • Calcium (Ca): Blood, bones & teeth; deficiency → rickets, osteoporosis.
    • Phosphorus (P): Bones, teeth, ATP, fluid balance.
    • Iron (Fe): Hemoglobin formation; deficiency → anemia; Egg Yellow.
    • Iodine (I): Thyroid hormones; deficiency → goitre.
    • Sodium & Potassium: Nerve impulse transmission, fluid/electrolyte balance, muscle contraction.
    • Magnesium, Zinc (liver & fish), Copper, Manganese, Cobalt: Enzymatic roles, synthesize RBC & B12.
  • Milk as Food: nearly complete food; 87% water; poor source of Vitamin C and iron.

Vitamins

Organic compounds; do not provide energy but essential for metabolism.

  • Fat-soluble vitamins: A, D, E, K → stored in body.
  • Water-soluble vitamins: B-complex, C → not stored (excreted in urine).

Vitamin A (Retinol)

  • Normal vision (rhodopsin formation in retina).
  • Deficiency: Night blindness (Nyctalopia), Xerophthalmia.
  • Sources: Carrot, spinach, papaya.

Vitamin B Complex

  • B1 (Thiamine):

    • Deficiency: Beri-Beri (muscle weakness, nerve degeneration).
    • Sources: Whole cereals, pulses, yeast.

  • B2 (Riboflavin):

    • Deficiency: Cheilosis (cracks at mouth corners), glossitis.
    • Sources: Egg, liver, leafy vegetables.

  • B3 (Niacin / Nicotinic acid):

    • Deficiency: Pellagra (3 Ds: dermatitis, diarrhea, dementia).

  • B5 (Pantothenic acid):

    • Deficiency: Fatigue, burning sensation (paraesthesia).

  • B6 (Pyridoxine):

    • Function: Amino acid metabolism.
    • Deficiency: Anemia, muscle weakness, dermatitis.

  • B7 (Biotin):

    • Function: Coenzyme in carboxylation reactions.
    • Deficiency: Skin disorders, hair loss.

  • B9 (Folic acid):

    • Function: Nucleic acid & hemoglobin synthesis.
    • Deficiency: Megaloblastic anemia.

  • B12 (Cyanocobalamin):

    • Function: DNA synthesis, nerve function.
    • Contains cobalt atoms.
    • Deficiency: Pernicious anemia, neurological disorders.
    • Sources: Generally not found in plants, but in fortified foods, synthesized by gut microbes.

Vitamin C (Ascorbic Acid)

  • Function: Collagen synthesis, antioxidant, enhances iron absorption, immunity booster.
  • Deficiency: Scurvy (bleeding gums, loose teeth, delayed wound healing).
  • Sources: Citrus fruits (orange, lemon), guava, amla (richest source).

Vitamin D (Calciferol)

  • Types: D₂ (ergocalciferol), D₃ (cholecalciferol).
  • Function: Regulates Ca & P absorption, bone formation.
  • Sources: Sunlight (skin synthesis), fish oil, egg yolk, milk.
  • Deficiency:
    • Rickets (children → bowed legs, weak bones).
    • Osteomalacia (adults → bone softening).
  • Note: The only vitamin like a hormone; body can synthesize completely (D & K).

Vitamin E (Tocopherol)

  • Function: Antioxidant, protects cell membranes, fertility.
  • Deficiency: Sterility, muscle degeneration.
  • Sources: Vegetable oils, nuts, soybean, sunflower seeds.

Vitamin K

  • Function: Blood clotting (synthesis of prothrombin).
  • Also synthesized by gut bacteria.

#Diseases

1. Viral Diseases

  • Polio: Poliovirus; transmitted via contaminated food/water, Salk vaccine, Sabin invented it. India polio-free (2014).
  • Rabies: From dog bite; virus infects nervous system; symptom → hydrophobia; CNS affected; Louis Pasteur.
  • Hepatitis: 5 types (A–E)
    • Hep A → Infectious Hepatitis, less dangerous, food/water
    • Hep B & C → blood/fluids (chronic damage to liver)
    • Hepatitis D is a defective virus that only infects individuals already infected with Hepatitis B
    • Vaccine available for Hepatitis B. (B is serum Hepatitis)
  • Jaundice: Excess bile pigmentation in liver; bile in blood increases; complete bedrest.
  • Herpes: Skin & mucous membrane.
  • Dengue Fever: Spread by Aedes aegypti; symptoms: high fever, rashes, low platelets.
  • Chikungunya: Spread by Aedes mosquito; joint pain, fever.
  • Zika Virus: Aedes mosquito; congenital microcephaly in infants.
  • Yellow Fever: Spread by Aedes.
  • Japanese Encephalitis: Spread by Culex mosquito; brain infection.
  • Common Cold: Rhinoviruses.
  • Influenza (Flu): Seasonal epidemics, mouthwash by Potassium permanganate.
  • Mumps: Salivary gland infection; swelling near ears; prevented by MMR vaccine.
  • Measles: Fever, rashes; prevented by MMR vaccine.
  • Chickenpox: Varicella-zoster virus.
  • Meningitis: By Enteroviruses; brain & spinal cord affected.
  • AIDS (Acquired Immunodeficiency Syndrome):
    • Virus: HIV (Retrovirus)
    • Transmission: blood transfusion, sexual contact, mother to child
    • Destroys immune system (T-helper cells)
    • No permanent cure; ART (antiretroviral therapy) used.
  • COVID-19: SARS-CoV-2; transmission: droplets, airborne, contact; Covaxin, Covishield, mRNA vaccines.
  • Ebola, Nipah Virus: Fatal outbreaks, no effective universal vaccine.

India's Achievements

  • Smallpox eradicated (1977 – Last case in 1975).
  • Guinea worm eradicated (2000).
  • Polio eradicated (2014).

2. Bacterial Diseases

  • Cholera → Vibrio cholerae; diarrhea, dehydration.
  • Typhoid → Salmonella typhi; intestinal ulcers, contaminated water & food. Intestinal fever.
  • Tuberculosis (TB) → Mycobacterium tuberculosis; blood in sputum.
  • Pneumonia → Streptococcus pneumoniae; lung inflammation.
  • Leprosy (Hansen’s Disease) → Mycobacterium leprae; skin lesions, nerve damage.
  • Plague → Yersinia pestis; transmitted by rat flea; bubonic plague (swollen lymph nodes).
  • Diphtheria → Corynebacterium diphtheriae; throat membrane formation.
  • Whooping Cough (Pertussis) → Bordetella pertussis; violent coughing.
  • Tetanus (Lockjaw) → Clostridium tetani; muscular spasms, jaw stiffness.
  • Syphilis → Treponema pallidum; sexually transmitted.
  • Gonorrhea → Neisseria gonorrhoeae; sexually transmitted.
  • Anthrax → Bacillus anthracis; zoonotic, also a bioterrorism agent.

3. Protozoan Diseases

  • Malaria: Caused by Plasmodium vivax, falciparum, malariae, ovale, Plasmodium knowlesi; vector = female Anopheles mosquito.
  • Amoebiasis: Entamoeba histolytica; dysentery, diarrhea.
  • Pyorrhoea: Pus through gums.
  • Diarrhoea: Frequent, loose watery stools.
  • Sleeping Sickness: Trypanosoma brucei; vector = Tsetse fly; affects brain.
  • Kala-azar (Visceral Leishmaniasis): Leishmania donovani; vector = sandfly; liver/spleen enlargement.

4. Fungal Diseases

  • Ringworm → Red, itchy patches on skin; caused by dermatophyte fungi, including Trichophyton, Microsporum, Epidermophyton.
  • Athlete’s Foot → Fungal infection between toes.
  • Candidiasis → Yeast infection (Candida albicans).
  • Aspergillosis → Lung infection by Aspergillus fungus.

5. Helminthic (Worm) Diseases

  • Ascariasis: Roundworm (Ascaris lumbricoides).
  • Filariasis (Elephantiasis): Wuchereria bancrofti; spread by Culex mosquito; swelling of legs/genitals.
  • Taeniasis: Tapeworm infection (Taenia solium, T. saginata).
  • Hookworm Disease: Ancylostoma duodenale; anemia due to blood loss.

6. Genetic Diseases

  • Hemophilia → Genetic bleeding disorder (X-linked); caused by mutations in genes affecting blood clotting.
  • Color Blindness → X-linked genetic condition for red-green; Non-X linked for blue-yellow.
  • Sickle Cell Anemia → Mutation in hemoglobin gene.
  • Microholes in Heart
  • Erythroblastosis Foetalis (Rh factor)
  • Sickle-cell Anaemia – Black Africans, tribes, RBC sickle-shaped.
  • Albinism – Fail to develop skin pigments.
  • Phenylketonuria – Unable to metabolize phenylalanine.

7. Lifestyle Diseases

  • Hypertension → Persistently high blood pressure.
  • Diabetes Mellitus → Due to insulin deficiency/resistance – glucose remains in blood rather than entering cells.
  • Arthritis → Joint inflammation, football player.
  • Cancer → Uncontrolled cell division, lump/thickening, malignant tumor; genetic, hormonal dysfunction, UV rays esp. whites (lack melanin). Retinoblastoma is eye cancer.
  • Obesity → Excess accumulation of fat.
  • Heart Attack → Coronary blockage.
  • Allergy → Skin & mucous membrane.

8. Other Human Diseases

  • Hemiplegia: Half body paralysed.
  • Diplopia: Eye muscle paralysis.
  • Epilepsy: Brain disorder.
  • Schizophrenia: Youngsters dreamy life.

Plant Diseases

Fungal

  • Rust of Wheat → Puccinia graminis.
  • Smut of Bajra (Pearl Millet) → Such as green ear disease, caused by Sclerospora graminicola (downy mildew) or Tolyposporium penicillariae (for grain smut).
  • Late Blight of Potato → Phytophthora infestans (caused Irish famine).

Bacterial

  • Citrus Canker → Xanthomonas citri.
  • Crown Gall Disease.

Viral

  • Tobacco Mosaic Virus (TMV).
  • Leaf Curl of Papaya.
  • Mosaic Disease in sugarcane, beans.
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