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Complete NCERT Biology — Cell Biology, Genetics, Evolution, Ecology, Human Physiology, Plant Physiology, Biotechnology.
| Feature | Prokaryotic Cell | Eukaryotic Cell |
|---|---|---|
| Size | 0.1–5.0 µm (small) | 5–100 µm (large) |
| Nucleus | Absent (nucleoid region only) | Well-defined, membrane-bound nucleus |
| Nuclear membrane | Absent | Present (double membrane with nuclear pores) |
| Chromosomes | Single circular DNA | Multiple linear chromosomes with histones |
| Membrane-bound organelles | Absent | Present (mitochondria, Golgi, ER, lysosomes) |
| Ribosomes | 70S (50S + 30S) | 80S (60S + 40S) |
| Cell wall | Present (peptidoglycan in bacteria) | Present in plants (cellulose), absent in animals |
| Plasma membrane | Present (no sterols except Mycoplasma) | Present (contains sterols like cholesterol) |
| Respiration | Mesosome (infolding of plasma membrane) | Mitochondria |
| Photosynthesis | Chromatophores / thylakoids (in cyanobacteria) | Chloroplasts |
| Vacuoles | Absent or small | Large central vacuole in plant cells |
| Cytoskeleton | Absent | Present (microtubules, microfilaments) |
| Cell division | Binary fission / amitosis | Mitosis / Meiosis |
| Examples | Bacteria, Archaea, Cyanobacteria | Plants, Animals, Fungi, Protists |
| Type | Mechanism | Energy | Direction | Examples |
|---|---|---|---|---|
| Simple diffusion | Movement from high to low concentration | No (passive) | Down concentration gradient | O₂, CO₂, H₂O (lipid-soluble) |
| Osmosis | Diffusion of water through semipermeable membrane | No (passive) | Hypotonic → Hypertonic | Water absorption by root hairs |
| Facilitated diffusion | Through channel/carrier proteins | No (passive) | Down gradient, specific | Glucose, amino acids, ions |
| Primary active transport | Pump proteins use ATP directly | Yes (ATP) | Against gradient | Na⁺/K⁺ pump, H⁺ pump |
| Secondary active transport | Uses electrochemical gradient from primary transport | Indirect | Against gradient | Na⁺-glucose co-transport (SGLT) |
| Bulk transport (exocytosis) | Vesicle fusion with plasma membrane | Yes (ATP) | Out of cell | Secretion of hormones, enzymes |
| Bulk transport (endocytosis) | Membrane engulfs substance to form vesicle | Yes (ATP) | Into cell | Phagocytosis (solid), Pinocytosis (liquid) |
| Receptor-mediated endo. | Specific receptor-ligand binding triggers uptake | Yes (ATP) | Into cell | Cholesterol uptake (LDL) |
Na⁺/K⁺ pump (Sodium-Potassium ATPase) moves 3 Na⁺ out and 2 K⁺ in per ATP consumed. It maintains resting membrane potential (~-70 mV), essential for nerve impulse transmission and secondary active transport.| Phase | Duration (typical) | Key Events |
|---|---|---|
| G1 Phase (Gap 1) | Variable (hours to years) | Cell growth, organelle duplication, protein synthesis; G1 checkpoint (restriction point) — commit to divide or enter G0 |
| S Phase (Synthesis) | ~6–8 hours | DNA replication (semiconservative); each chromosome becomes two sister chromatids; centrioles replicate in animal cells |
| G2 Phase (Gap 2) | ~3–4 hours | Cell continues to grow; synthesis of microtubules, proteins needed for mitosis; G2 checkpoint checks DNA replication completeness |
| M Phase (Mitotic) | ~1 hour | Division of nucleus (karyokinesis) and cytoplasm (cytokinesis); produces 2 identical daughter cells (2n) |
| G0 Phase (Quiescent) | Indefinite | Cells exit cycle; metabolically active but do not divide; e.g., neurons, liver cells (can re-enter), lymphocytes |
| Stage | Key Events | Chromosome Status |
|---|---|---|
| Prophase | Chromatin condenses into chromosomes; nucleolus disappears; centrioles move to poles; spindle fibres form; nuclear envelope starts to disintegrate | Each chromosome = 2 sister chromatids joined at centromere |
| Metaphase | Chromosomes align at metaphase plate (cell equator); spindle fibres attach to kinetochores; chromosomes maximally condensed — best for karyotyping | 2n chromosomes, each with 2 chromatids |
| Anaphase | Centromere splits; sister chromatids separate and move to opposite poles (shortening of spindle fibres); chromosomes are now V-shaped | Each pole gets 2n chromosomes (1 chromatid each) |
| Telophase | Chromosomes decondense into chromatin; nuclear envelope re-forms; nucleolus reappears; spindle fibres disappear | Nuclear division complete; 2 nuclei formed |
| Cytokinesis | Cytoplasmic division: animal — cleavage furrow (actin ring); plant — cell plate formation (Golgi vesicles) | 2 identical diploid (2n) daughter cells |
| Stage | Key Events | Chromosome No. |
|---|---|---|
| Meiosis I: Prophase I | Longest phase; synapsis (pairing of homologous chromosomes); crossing over (exchange of segments between non-sister chromatids); tetrads/bivalents form | 2n (diploid) — homologous pairs |
| Meiosis I: Metaphase I | Tetrads align at equator; spindle fibres attach to kinetochores of homologous chromosomes | 2n (paired) |
| Meiosis I: Anaphase I | Homologous chromosomes separate (sister chromatids remain attached); move to opposite poles | n (haploid) at each pole — but each has 2 chromatids |
| Meiosis I: Telophase I | Two haploid nuclei form; may have brief interkinesis (no DNA replication) | n |
| Meiosis II: Prophase II | Chromosomes condense again; spindle fibres form; nuclear envelope breaks down | n (each chromosome = 2 chromatids) |
| Meiosis II: Metaphase II | Chromosomes align at equator singly (no tetrads) | n |
| Meiosis II: Anaphase II | Centromeres split; sister chromatids separate to opposite poles | n chromatids at each pole |
| Meiosis II: Telophase II | 4 haploid nuclei form; cytokinesis produces 4 daughter cells | n (haploid) — 4 unique gametes |
| Type | Formula | Classification | Examples | Functions |
|---|---|---|---|---|
| Monosaccharides | Cₙ(H₂O)ₙ | Triose (3C), Pentose (5C), Hexose (6C) | Glucose (C₆H₁₂O₆), Fructose, Galactose, Ribose, Deoxyribose | Energy source, building blocks; Ribose in RNA, Deoxyribose in DNA |
| Oligosaccharides | — | 2–10 sugar units | Sucrose (glucose+fructose), Lactose (glucose+galactose), Maltose | Transport, energy; Sucrose = transport sugar in plants |
| Polysaccharides | (C₆H₁₀O₅)ₙ | Homopolymers, Heteropolymers | Starch (amylose+amylopectin), Glycogen, Cellulose, Chitin | Storage (starch, glycogen), structural (cellulose, chitin) |
| Simple lipids | — | Triglycerides, Waxes | Fats (stearic, palmitic), Oils (oleic, linoleic) | Energy storage (9 kcal/g), insulation, protection |
| Compound lipids | — | Phospholipids, Glycolipids | Lecithin, Cephalin, Sphingomyelin | Cell membrane structure, myelin sheath |
| Steroids | — | Sterols, Bile acids | Cholesterol, Testosterone, Estrogen, Vitamin D | Hormones, membrane fluidity, bile salts |
| Level | Description | Bonds | Example |
|---|---|---|---|
| Primary | Linear sequence of amino acids linked by peptide bonds | Peptide (covalent) bonds | Insulin — 51 amino acids |
| Secondary | Local folding into α-helix (right-handed) or β-pleated sheet | Hydrogen bonds between backbone C=O and N-H | Keratin (α-helix), Silk fibroin (β-sheet) |
| Tertiary | 3D folding of entire polypeptide chain into globular shape | H-bonds, disulfide bridges, ionic, hydrophobic, van der Waals | Myoglobin, enzymes |
| Quaternary | Association of 2+ polypeptide subunits into functional protein | Same bonds as tertiary + hydrophobic interactions | Haemoglobin (α₂β₂), DNA polymerase |
Proto-oncogenes — normal genes that promote cell division; when mutated → oncogenes (overactive, cause cancer). (2) Tumour suppressor genes — normal genes that inhibit uncontrolled division; when mutated → loss of control. (3) p53 gene — "guardian of the genome"; most commonly mutated gene in human cancers. Cancer detection: biopsy, CT/MRI, antigen markers (PSA for prostate). Treatments: surgery, chemotherapy (anti-mitotic drugs), radiotherapy, immunotherapy.| Type | Mechanism | Reversibility | Example |
|---|---|---|---|
| Competitive inhibition | Inhibitor structurally similar to substrate; binds active site | Reversible (by excess substrate) | Malonate inhibits succinate dehydrogenase |
| Non-competitive inhibition | Inhibitor binds allosteric site (not active site); changes enzyme shape | Usually irreversible | Cyanide inhibits cytochrome oxidase |
| Uncompetitive inhibition | Inhibitor binds only to enzyme-substrate complex | Reversible | Lithium inhibits inositol monophosphatase |
| Feedback inhibition | End product of pathway inhibits earlier enzyme; regulates metabolic pathways | Reversible | ATP inhibits phosphofructokinase (glycolysis) |
| Allosteric regulation | Effector binds regulatory site; induces conformational change | Reversible | Hemoglobin O₂ binding (cooperative) |
| Law | Statement | Basis | Exception |
|---|---|---|---|
| Law of Dominance | In a heterozygous pair, one allele is dominant and masks the expression of the recessive allele | F1 shows only dominant trait; recessive reappears in F2 | Incomplete dominance, Codominance |
| Law of Segregation | Allele pairs separate (segregate) during gamete formation so each gamete receives only one allele | Anaphase I of meiosis — homologous chromosomes separate | Linked genes (do not segregate independently) |
| Law of Independent Assortment | Genes for different traits assort independently of one another during gamete formation | Metaphase I — random alignment of homologous pairs | Linked genes on same chromosome |
| Type | Description | Example | F2 Ratio |
|---|---|---|---|
| Incomplete dominance | Heterozygote shows intermediate phenotype between two homozygotes | Snapdragon: Red (RR) × White (rr) → Pink (Rr) | 1:2:1 (genotypic + phenotypic) |
| Codominance | Both alleles express themselves fully in heterozygote; no blending | Blood group AB (IᴬIᴮ); Roan coat in cattle (red + white hairs) | 1:2:1 |
| Multiple alleles | More than 2 alleles for a single gene in a population | ABO blood groups (Iᴬ, Iᴮ, i); Drosophila eye colour | Various |
| Pleiotropy | Single gene affects multiple, seemingly unrelated phenotypic traits | Phenylketonuria (PKU) — affects brain, skin, hair colour | — |
| Polygenic inheritance | Single trait controlled by 2+ genes with additive effect; continuous variation | Human skin colour, height, eye colour | Bell-shaped curve (normal distribution) |
| Epistasis | One gene masks/modifies the expression of another non-allelic gene | Labrador coat colour (E gene masks B gene) | Modified ratios (9:3:4, 12:3:1, 9:7) |
| System | Mechanism | Male | Female | Examples |
|---|---|---|---|---|
| XX-XY | Male heterogametic (2 types of sperm) | XY | XX | Humans, Drosophila |
| ZZ-ZW | Female heterogametic (2 types of eggs) | ZZ | ZW | Birds, Fish, Reptiles, some insects |
| XO type | Number of X chromosomes determines sex | XO (1X) | XX (2X) | Grasshoppers, Cockroaches |
| Haplo-diploidy | Fertilized eggs = female; unfertilized = male | Haploid (n) | Diploid (2n) | Bees, Ants, Wasps |
| Type | Description | Effect |
|---|---|---|
| Deletion | Loss of a chromosome segment | Cri-du-chat syndrome (deletion on chr 5) |
| Duplication | A segment is repeated | Gene dosage effect; may cause developmental issues |
| Inversion | Segment breaks and reattaches in reverse order | Position effect; may disrupt gene function |
| Translocation | Segment moves to a non-homologous chromosome | Chronic myeloid leukemia (Philadelphia chr 9;22) |
| Aneuploidy | Gain or loss of individual chromosomes | Down syndrome (Trisomy 21), Turner (XO), Klinefelter (XXY) |
| Polyploidy | Extra complete set(s) of chromosomes | Common in plants (wheat = hexaploid); lethal in humans |
| Experiment | Scientist(s) | Organism | Key Finding |
|---|---|---|---|
| Transformation | Griffith (1928) | Streptococcus pneumoniae | R strain → S strain transformation by some "transforming principle" (heat-stable) |
| Biochemical | Avery, MacLeod, McCarty (1944) | S. pneumoniae | Identified DNA as transforming principle (protease/RNase didn't destroy it; DNase did) |
| Hershey-Chase | Hershey & Chase (1952) | T₂ bacteriophage + E. coli | ³²P (DNA) entered bacteria; ³⁵S (protein) did not → DNA is genetic material |
| Transduction | Lederberg & Zinder (1952) | Salmonella + P22 phage | Bacteriophage transfers bacterial DNA between cells |
| Stage | Event | Enzyme / Factor |
|---|---|---|
| Initiation | RNA polymerase binds promoter; σ factor (in bacteria) recognizes -35 and -10 boxes; DNA unwinds to form transcription bubble | RNA polymerase + σ factor (bacteria) or TFIID + other factors (eukaryotes) |
| Elongation | RNA polymerase synthesizes mRNA in 5'→3' direction using template strand (3'→5'); complementary base pairing (A-U instead of A-T) | RNA polymerase (core enzyme) |
| Termination | In bacteria: rho-dependent or rho-independent termination; in eukaryotes: poly-A signal (AAUAAA) | ρ factor (bacteria) or cleavage + polyadenylation (eukaryotes) |
| Post-transcriptional | 5' capping (7-methylguanosine), 3' polyadenylation (~200 A residues), splicing (removal of introns by spliceosome) | Spliceosome (snRNA + proteins), poly-A polymerase |
| Property | Description | Example / Detail |
|---|---|---|
| Triplet | Each codon has 3 nucleotides; 64 possible codons | AUG, UUU, GCA, etc. |
| Universal | Same codons code for same amino acids in nearly all organisms | AUG = Methionine (Start) in all organisms |
| Degenerate / Redundant | Most amino acids are coded by more than one codon | Leucine: UUA, UUG, CUU, CUC, CUA, CUG (6 codons) |
| Unambiguous | One codon codes for only one specific amino acid | UUU always = Phenylalanine |
| Non-overlapping | Codons are read sequentially without sharing bases | AUG|CUA|GGA (not AUG|UGC|UAG...) |
| Commaless | No punctuation between codons; continuous reading frame | AUGCUAGGACUU → AUG|CUA|GGA|CUU |
| Start codon | AUG (Methionine) — initiation of translation | Also codes for Met in internal positions |
| Stop codons | UAA, UAG, UGA — no tRNA; signal termination | Do not code for any amino acid (nonsense codons) |
U Are Away — UAA, UAG, UGA. These are the three nonsense codons that do not code for any amino acid and signal termination of translation. Also remember: AUG is the START codon (codes for Methionine). The genetic code is nearly universal — the same codons code for the same amino acids in bacteria, plants, and humans.| Evidence Type | Description | Examples |
|---|---|---|
| Paleontological | Study of fossils — preserved remains/traces of organisms | Archaeopteryx (bird-reptile link), horse evolution (Eohippus → Equus), Trilobite fossils |
| Morphological (homology) | Similar structure, different function; common ancestry | Forelimbs of whale, bat, human, cheetah — same bones (humerus, radius, ulna) |
| Morphological (analogy) | Similar function, different structure & origin; convergent evolution | Wings of butterfly (insect) and bat (mammal); eyes of octopus and mammals |
| Anatomical | Vestigial organs (remnants with no current function) | Vermiform appendix, coccyx (tail bone), wisdom teeth, pelvic bones in snakes |
| Biochemical | Similar molecular composition across organisms | Universal genetic code, same 20 amino acids, cytochrome c similarity, ATP as energy currency |
| Embryological | Similar embryonic development in different organisms | Pharyngeal gill slits in fish, chick, human embryos; tail in human embryo |
| Biogeographical | Geographic distribution supports evolution | Marsupials in Australia (isolated); Darwin's finches (Galapagos) |
| Aspect | Lamarckism (1809) | Darwinism (1859) | Neo-Darwinism (Synthetic Theory) |
|---|---|---|---|
| Proposed by | Jean-Baptiste Lamarck | Charles Darwin (On Origin of Species) | Fisher, Haldane, Wright, Mayr, Stebbins |
| Core idea | Inheritance of acquired characteristics | Natural selection | Natural selection + Genetics + Population dynamics |
| Mechanism | Use and disuse of organs → acquired traits inherited | Variation exists → fittest survive → reproduce | Mutation + recombination + natural selection + genetic drift + gene flow + isolation |
| Key concepts | Giraffe neck elongated by stretching | Struggle for existence; survival of the fittest | Population genetics; Hardy-Weinberg; speciation |
| Status | Largely disproved (Weismann experiment) | Partially correct (mechanism was unknown) | Currently accepted theory of evolution |
| Type | Description | Effect | Example |
|---|---|---|---|
| Stabilizing | Favors intermediate phenotypes; eliminates extremes | Reduces variation | Human birth weight (low/high = higher mortality) |
| Directional | Favors one extreme phenotype | Shifts mean in one direction | Industrial melanism (peppered moth — dark favored in polluted areas) |
| Disruptive | Favors both extreme phenotypes over intermediate | Bimodal distribution; may lead to speciation | Beak size in Darwin's finches during drought |
| Species | Period | Key Features | Location |
|---|---|---|---|
| Dryopithecus | 25–15 mya | Ape-like; arboreal; ancestors of apes and humans | Europe, Africa, Asia |
| Ramapithecus | 15–14 mya | Upright posture; possible ancestor of hominids | Siwalik Hills (India) |
| Australopithecus | 4.5–1.5 mya | Bipedal (walked upright); small brain (~450 cc); gracile | East & South Africa |
| Homo habilis | 2.4–1.5 mya | First tool maker ("Handy man"); brain ~650–800 cc | Africa |
| Homo erectus | 1.9–0.1 mya | Upright walker; used fire; tools (Acheulian); brain ~900 cc | Africa, Asia, Europe |
| Homo neanderthalensis | 0.4–0.03 mya | Large brain (~1450 cc); buried dead; cared for injured | Europe, West Asia |
| Homo sapiens | 0.2 mya – present | Modern humans; large brain (~1350 cc); language, culture, art | Originated in Africa; migrated worldwide |
Industrial melanism — Biston betularia (peppered moth). Before industrialization: white moths survived better on lichen-covered trees. After industrialization: dark (melanistic) moths survived better on soot-covered trees. This is a classic example of directional selection observed in nature.| Organ | Location | Key Role | Enzymes / Secretions |
|---|---|---|---|
| Mouth (Oral cavity) | Begin digestive tract | Mechanical breakdown; starch digestion begins | Salivary amylase (ptyalin) → starch → maltose |
| Teeth | In jaws (32 in adults) | Mastication (chewing); 4 types: incisor, canine, premolar, molar | — |
| Tongue | Floor of mouth | Taste buds (sweet, salty, sour, bitter, umami); mixing food with saliva | Lingual lipase (minor) |
| Oesophagus | Between pharynx and stomach | Peristalsis moves food bolus to stomach | Mucus (lubrication) |
| Stomach | Upper left abdomen | Protein digestion; churning; HCl kills bacteria; intrinsic factor | HCl, Pepsinogen → Pepsin, Rennin (infants), Gastric lipase, Mucus |
| Small intestine | Between stomach & large intestine | Major site of digestion & absorption; ~6m long | Trypsin, Chymotrypsin, Amylase, Lipase, Maltase, Lactase, Sucrase, Peptidases, Nucleases |
| Large intestine | End of digestive tract | Water & electrolyte absorption; faeces formation | Mucus; bacteria produce Vitamin K, B12 |
| Rectum & Anus | Terminal end | Storage and expulsion of faeces | — |
| Component | Description | Key Facts |
|---|---|---|
| Nostrils / Nasal cavity | Air entry; filters, warms, moistens air; olfaction | Hairs and mucus trap dust/particles |
| Pharynx | Common passage for air and food | Nasopharynx, Oropharynx, Laryngopharynx |
| Larynx (voice box) | Contains vocal cords; sound production | Epiglottis prevents food entry into trachea |
| Trachea | Cartilage-ringed tube; divides into bronchi | C-rings of cartilage keep it open |
| Bronchi & Bronchioles | Branching tubes leading to alveoli | Bronchioles lack cartilage; have smooth muscle |
| Alveoli | Tiny air sacs — primary site of gas exchange | ~300 million; surrounded by capillary network; 1-cell thick walls |
| Diaphragm | Dome-shaped muscle separating thorax & abdomen | Contraction → inspiration; relaxation → expiration |
| Volume / Capacity | Value (adult male) | Definition |
|---|---|---|
| Tidal Volume (TV) | ~500 mL | Volume of air inhaled/exhaled in normal quiet breathing |
| Inspiratory Reserve (IRV) | ~2500–3000 mL | Additional air that can be inhaled after normal inspiration |
| Expiratory Reserve (ERV) | ~1000–1100 mL | Additional air that can be exhaled after normal expiration |
| Residual Volume (RV) | ~1100–1200 mL | Air remaining in lungs after maximum expiration (never fully emptied) |
| Inspiratory Capacity | TV + IRV ≈ 3500 mL | Maximum air that can be inhaled after normal expiration |
| Functional Residual Capacity | ERV + RV ≈ 2300 mL | Air remaining after normal expiration |
| Vital Capacity | TV + IRV + ERV ≈ 4600 mL | Maximum air that can be exhaled after maximum inspiration |
| Total Lung Capacity | VC + RV ≈ 5800 mL | Total volume of air in lungs after maximum inspiration |
| Component | Value / Description | Function |
|---|---|---|
| Plasma (55%) | Straw-coloured fluid: 90–92% water, proteins (albumin, globulin, fibrinogen), electrolytes, nutrients, hormones, wastes | Transport medium; osmotic balance; clotting; immunity |
| RBC (Erythrocytes) | ~5–5.5 million/mm³; biconcave disc; no nucleus; lifespan 120 days; formed in red bone marrow | Transport O₂ and CO₂ (haemoglobin — Fe²⁺; 4 O₂ per Hb) |
| WBC (Leucocytes) | ~6000–8000/mm³; nucleated; formed in bone marrow, lymph nodes; lifespan varies | Immune defence: Neutrophils (phagocytosis), Lymphocytes (antibodies), Monocytes (macrophages), Eosinophils (allergy), Basophils (histamine) |
| Platelets (Thrombocytes) | ~2.5–3.5 lakh/mm³; cell fragments from megakaryocytes; no nucleus; lifespan ~10 days | Blood clotting (release thromboplastin/thrombokinase) |
| Blood Group | Antigen on RBC | Antibody in Plasma | Can Donate To | Can Receive From |
|---|---|---|---|---|
| A | A (Iᴬ) | Anti-B (b) | A, AB | A, O |
| B | B (Iᴮ) | Anti-A (a) | B, AB | B, O |
| AB | A and B (IᴬIᴮ) | None | AB (universal recipient) | A, B, AB, O |
| O | None | Anti-A and Anti-B | A, B, AB, O (universal donor) | O |
| Rh+ | Rh antigen (D) | None | Rh+ only | Rh+ or Rh− |
| Rh− | No Rh antigen | Anti-Rh (if sensitized) | Rh+ or Rh− | Rh− only |
| Process | Site | Description | Key Mechanism |
|---|---|---|---|
| Glomerular filtration | Glomerulus | Blood filtered under high pressure (~55 mmHg); filtrate = water + small solutes (glucose, amino acids, urea, ions) | Net filtration pressure = GHP (55) − [(BCOP 30) + CPS (15)] = 10 mmHg; GFR = 125 mL/min = 180 L/day |
| Tubular reabsorption | PCT, LOH, DCT, CD | Selective reabsorption of useful substances back into peritubular capillary blood | Active transport (Na⁺, glucose, amino acids); passive (water follows Na⁺); 99% water reabsorbed |
| Tubular secretion | PCT, DCT, CD | Active secretion of H⁺, K⁺, ammonia, drugs, toxins from blood into tubular fluid | Maintains acid-base balance, removes substances not filtered; important for drug clearance |
| Gland | Hormone(s) | Source Cells | Functions |
|---|---|---|---|
| Pituitary (Anterior) | GH, PRL, TSH, ACTH, FSH, LH, MSH | Adenohypophysis | Growth; lactation; stimulates thyroid, adrenal cortex, gonads; skin pigmentation |
| Pituitary (Posterior) | ADH (Vasopressin), Oxytocin | Neurohypophysis (stores hypothalamic hormones) | Water reabsorption in kidney; uterine contraction, milk ejection |
| Pituitary (Intermediate) | MSH | Pars intermedia | Skin pigmentation in lower vertebrates |
| Thyroid | T₃ (Triiodothyronine), T₄ (Thyroxine), Calcitonin | Thyroid follicles; C cells | BMR regulation; growth & development; Ca²⁺ lowering |
| Parathyroid | PTH (Parathyroid hormone) | Parathyroid glands (4) | Increases blood Ca²⁺; activates osteoclasts; stimulates kidney Ca²⁺ reabsorption |
| Thymus | Thymosins | Thymus epithelial cells | T-lymphocyte maturation; cell-mediated immunity |
| Adrenal (Cortex) | Glucocorticoids (Cortisol), Mineralocorticoids (Aldosterone), Sex corticoids | Zona fasciculata, glomerulosa, reticularis | Anti-inflammatory, stress response; Na⁺/K⁺ balance; secondary sex characters |
| Adrenal (Medulla) | Adrenaline (Epinephrine), Noradrenaline | Chromaffin cells | Fight-or-flight response; increases heart rate, BP, blood sugar; dilates pupils |
| Pancreas (Islets) | Insulin (β-cells), Glucagon (α-cells), Somatostatin (δ-cells) | Islets of Langerhans | Lowers blood glucose (glycogenesis); raises blood glucose (glycogenolysis); inhibits both |
| Testis | Testosterone (Leydig cells), Inhibin (Sertoli cells) | Leydig cells, Sertoli cells | Spermatogenesis, male secondary sex characters; inhibits FSH |
| Ovary | Estrogen (Graafian follicle), Progesterone (Corpus luteum) | Theca interna, Corpus luteum | Female secondary sex characters, uterine growth; maintains pregnancy, mammary gland development |
| Pineal | Melatonin | Pinealocytes | Regulates circadian rhythm (24-hr sleep-wake cycle); influences metabolism and pigmentation |
| Feature | Innate Immunity | Adaptive (Acquired) Immunity |
|---|---|---|
| Nature | Non-specific; present from birth | Specific; develops after exposure to antigen |
| Components | Physical barriers (skin, mucosa), physiological (pH, temperature), cellular (macrophages, neutrophils, NK cells), inflammatory response, fever | B-lymphocytes (antibody-mediated/humoral), T-lymphocytes (cell-mediated) |
| Memory | No memory; same response every time | Immunological memory — stronger and faster response on second exposure |
| Response time | Immediate (minutes to hours) | Delayed initially (5-7 days); faster on subsequent exposure |
| Types of T cells | Not applicable | Helper T cells (CD4⁺ — activate B cells, cytotoxic T cells), Cytotoxic T cells (CD8⁺ — kill virus-infected/cancer cells), Memory T cells, Suppressor T cells |
| Types of antibodies | Not applicable | IgG (most abundant, crosses placenta), IgA (secretions — saliva, tears, colostrum), IgM (first antibody produced, pentamer), IgE (allergy, parasitic infections), IgD (B cell surface receptor) |
| Vaccination | Not applicable | Introduces weakened/killed pathogen or antigen → primary response → memory cells formed → protection on future exposure (Edward Jenner — smallpox, 1796) |
| Disorders | — | Autoimmune (body attacks self: Rheumatoid arthritis, Lupus), Immunodeficiency (SCID, AIDS — HIV destroys CD4⁺ T cells), Allergy (IgE-mediated — histamine release) |
Hypothyroidism in pregnancy → Cretinism (stunted growth, mental retardation). (2) Hyperthyroidism → Exophthalmic goitre / Graves' disease. (3) Hyposecretion of insulin → Diabetes mellitus (high blood sugar, glycosuria). (4) Hypersecretion of GH in children → Gigantism; in adults → Acromegaly. (5) Hyposecretion of GH in children → Pituitary dwarfism.| Process | Description | Mechanism | Key Points |
|---|---|---|---|
| Diffusion | Movement of molecules from high to low concentration | Passive; no energy required | Faster in gases > liquids > solids; affected by concentration gradient, temperature, surface area |
| Osmosis | Movement of water through semipermeable membrane from hypotonic to hypertonic solution | Passive | Osmotic pressure = minimum pressure to prevent osmosis; OP ∝ solute concentration |
| Plasmolysis | Shrinking of cell membrane from cell wall when cell placed in hypertonic solution | Water leaves the cell | Useful to determine if a cell is alive or dead; reversible if placed back in hypotonic solution |
| Imbibition | Absorption of water by solid particles (seeds, wood) causing swelling | Adsorption; colloidal system | Requires affinity between substance and water; heat is released; seeds imbibe water before germination |
| Transpiration pull | Water column pulled upward due to transpiration from leaves | Cohesion-adhesion-tension | Main driving force for water ascent in tall plants (Dixon & Joly, 1894) |
| Root pressure | Positive hydrostatic pressure developed in roots due to active water uptake | Active transport; osmotic | Pushes water upward (max ~2 atm); contributes to guttation; minor role in tall plants |
| Capillarity | Rise of water in narrow tubes due to surface tension and adhesion | Physical | Minor role; xylem vessels are too wide for significant capillary rise |
| Element | Type | Functions | Deficiency Symptoms |
|---|---|---|---|
| Nitrogen (N) | Macro (C, H, O excluded) | Component of proteins, nucleic acids, chlorophyll, hormones | Chlorosis (yellowing of older leaves), stunted growth, reduced flowering |
| Phosphorus (P) | Macro | Component of ATP, NADP, nucleic acids, phospholipids | Poor root growth, purple leaves, delayed maturity |
| Potassium (K) | Macro | Osmoregulation, stomatal opening, enzyme activation | Necrosis at leaf tips and margins, wilting |
| Calcium (Ca) | Macro | Middle lamella (calcium pectate), cell wall structure | Chlorosis at leaf tips, crinkling of leaves |
| Magnesium (Mg) | Macro | Central atom of chlorophyll; enzyme activator | Chlorosis (interveinal — between veins); green veins |
| Sulphur (S) | Macro | Component of amino acids (cysteine, methionine), coenzymes | Chlorosis of young leaves |
| Iron (Fe) | Micro | Chlorophyll synthesis, electron carrier (cytochromes) | Interveinal chlorosis (young leaves); green veins |
| Manganese (Mn) | Micro | Water splitting in PS II, enzyme activator | Necrotic spots on leaves |
| Zinc (Zn) | Micro | Auxin synthesis, enzyme activator (carbonic anhydrase) | Little leaf (small leaves), rosette formation |
| Boron (B) | Micro | Pollen germination, cell elongation, sugar transport | Death of stem/root apical meristem, heart rot of beetroot |
| Molybdenum (Mo) | Micro | Nitrogen fixation (nitrogenase), nitrate reductase enzyme | Whiptail disease in cauliflower (molybdenum cofactor deficiency) |
| Copper (Cu) | Micro | Plastocyanin (electron transport), lignin synthesis | Dieback of shoots, dark green leaves |
| Component | Location | Key Events |
|---|---|---|
| PS II (P680) | Thylakoid membrane (inner) | Absorbs light at 680 nm; water photolysis (H₂O → 2H⁺ + ½O₂ + 2e⁻); electrons pass through ETS; donor = water |
| Electron Transport System | Thylakoid membrane | PQ (Plastoquinone) → Cyt b₆f → PC (Plastocyanin); protons pumped into lumen → proton gradient |
| PS I (P700) | Thylakoid membrane (outer) | Absorbs light at 700 nm; re-excites electrons from PC; electrons passed to ferredoxin → NADP⁺ reductase |
| NADP⁺ reductase | Stroma side of thylakoid | Reduces NADP⁺ + H⁺ → NADPH using electrons from ferredoxin |
| Photophosphorylation | CF₀-CF₁ ATP synthase | Protons flow back through ATP synthase → ADP + Pi → ATP (chemiosmotic theory by Peter Mitchell) |
| Z-scheme | Overall | Non-cyclic: PS II → ETS → PS I → NADPH + ATP + O₂; Cyclic: PS I only → ATP (no NADPH, no O₂) |
| Feature | C₃ Plants | C₄ Plants | CAM Plants |
|---|---|---|---|
| First stable product | 3-carbon compound (3PGA) | 4-carbon compound (OAA / Oxaloacetate) | 3-carbon (3PGA) but at night: OAA → Malic acid |
| Enzyme for CO₂ fixation | RuBisCO | PEP carboxylase (initially), then RuBisCO | PEP carboxylase (night), RuBisCO (day) |
| Kranz anatomy | Absent | Present (bundle sheath cells around vascular bundle) | Absent |
| Photorespiration | Significant (losses 25-50% fixed carbon) | Negligible (CO₂ concentrator mechanism) | Negligible (temporal separation) |
| Optimal temperature | 15-25°C | 30-40°C | High temperature, arid conditions |
| CO₂ compensation point | 25-100 ppm | 0-10 ppm | Very low at night |
| Examples | Wheat, Rice, Soybean, Oats, Potato | Maize, Sugarcane, Sorghum, Amaranthus | Pineapple, Opuntia, Kalanchoe, Orchids |
| Productivity | Lower (photorespiratory losses) | Higher (no photorespiration) | Moderate |
| Hormone | Source | Functions | Applications |
|---|---|---|---|
| Auxin (IAA) | Shoot apex, young leaves, developing seeds | Cell elongation (acid growth hypothesis), apical dominance, root initiation, phototropism, geotropism, xylem differentiation, parthenocarpy | Rooting powder (IBA, NAA), weedicides (2,4-D), parthenocarpic fruits |
| Gibberellins (GA) | Young leaves, root tips, developing seeds | Stem elongation (bolting), seed germination (breaks dormancy), flowering in LD plants, parthenocarpy, enzyme α-amylase production in germinating seeds | Dwarf pea → tall (GA treatment); malting of barley; early seed germination |
| Cytokinins | Root apex (mainly) | Cell division (cytokinesis), delay leaf senescence, promote chloroplast development, shoot formation in tissue culture, overcome apical dominance | Tissue culture (callus → shoot), prolonging shelf life of vegetables, crop yield |
| Ethylene (C₂H₄) | Ripening fruits, senescing tissues, stressed tissues | Fruit ripening, leaf abscission, senescence, promotes flowering in pineapple, epinasty (downward bending of leaves), root hair growth | Artificial fruit ripening (ethylene gas), rubber latex flow, degreening citrus |
| ABA (Abscisic acid) | Leaves, stem, green fruit | Growth inhibitor; seed dormancy; stomatal closure (anti-transpirant); abscission; stress hormone (drought, cold) | Seed storage, antitranspirant, winter dormancy induction |
Photoperiodism — response of plants to duration of light/dark. SDP (Short Day Plants) flower when day length < critical period (e.g., Chrysanthemum, Rice). LDP (Long Day Plants) flower when day length > critical period (e.g., Wheat, Radish). Vernalization — cold treatment (0-5°C) of seeds/plants to promote flowering (e.g., Winter wheat, Rye, Beetroot); discovered by Lysenko.| Model | Equation | Curve Shape | Conditions | Examples |
|---|---|---|---|---|
| Exponential (J-shaped) | dN/dt = rN | J-shaped curve | Unlimited resources (ideal conditions); constant r (intrinsic rate of natural increase) | Early phase of bacterial growth, algae bloom, invasive species |
| Logistic (S-shaped) | dN/dt = rN(K−N)/K | Sigmoid curve | Limited resources; carrying capacity (K) is maximum population size the environment can sustain | Most natural populations; yeast in lab; island populations |
| Interaction | Species A | Species B | Description | Example |
|---|---|---|---|---|
| Predation | + (benefit) | − (harm) | One organism kills and eats another | Lion eats deer; Pisaster starfish controls mussel population (keystone species) |
| Competition | − (harm) | − (harm) | Both compete for same limited resources | Paramecium (Gause's competitive exclusion principle — one eliminates other) |
| Parasitism | + (benefit) | − (harm) | Parasite lives on/in host, derives nutrition | Tapeworm in human intestine; Cuscuta on host plant; Brood parasitism (koel in crow nest) |
| Commensalism | + (benefit) | 0 (neutral) | One benefits, other unaffected | Orchid on tree (epiphyte); Barnacles on whale; Cattle egret near cattle |
| Mutualism | + (benefit) | + (benefit) | Both species benefit | Lichen (algae + fungi); Mycorrhiza (fungus + root); Rhizobium in legume roots; Fig-wasp pollination |
| Amensalism | 0 (neutral) | − (harm) | One unaffected, other harmed | Large tree shades small plant (allelopathy); antibiosis (Penicillium kills bacteria) |
| Cycle | Reservoir / Source | Key Processes | Human Impact |
|---|---|---|---|
| Carbon cycle | Atmosphere (CO₂ — 0.03%), fossil fuels, ocean | Photosynthesis (CO₂ fixation); respiration (CO₂ release); combustion; decomposition; ocean absorption | Burning fossil fuels, deforestation → increased CO₂ → global warming (greenhouse effect) |
| Nitrogen cycle | Atmosphere (N₂ — 78%), soil, biomass | N₂ fixation (atmospheric, biological by Rhizobium, Azotobacter; industrial Haber process); Nitrification (Nitrosomonas → Nitrobacter); Assimilation; Ammonification; Denitrification (Pseudomonas) | Excessive fertilizer use → eutrophication; Haber process uses fossil fuels |
| Phosphorus cycle | Rocks (sedimentary deposits), ocean sediments | Weathering of rocks → PO₄³⁻ in soil → plant absorption → animal consumption → decomposition → mineralization; no atmospheric phase | Excessive phosphate mining → algal blooms; non-renewable (slow cycle) |
| Type | Starting Point | Intermediate Stages | Climax Community | Example |
|---|---|---|---|---|
| Primary succession | Barren, lifeless substrate (no soil) — lava, sand, rock | Lichens & mosses (pioneer) → herbs → grasses → shrubs → trees | Stable, self-sustaining community (forest) | Surtsey Island (Iceland, volcanic); Glacier retreat succession |
| Secondary succession | Previously inhabited area with soil (after disturbance) | Faster than primary; grasses → shrubs → trees | Climax community | Forest after fire; abandoned farmland; regrowth after flood |
| Concept | Description | Examples / Details |
|---|---|---|
| Food chain | Linear sequence of organisms where each is food for the next; energy flows from T1 → T2 → T3 → T4 | Grass → Grasshopper → Frog → Snake → Hawk (Grazing chain); Detritus → Earthworm → Sparrow (Detritus chain) |
| Food web | Network of interconnected food chains; more complex and stable than single food chain | Most natural ecosystems have food webs; provides multiple feeding options |
| Trophic levels | Feeding positions in food chain: T1 (producers), T2 (primary consumers/herbivores), T3 (secondary consumers), T4 (tertiary consumers) | Energy decreases at each level (~10% transfer); number of trophic levels usually limited to 3-4 |
| 10% Law (Lindeman) | Only ~10% of energy at one trophic level is transferred to the next; rest lost as heat, respiration, excretion | If producers have 10,000 J → herbivores get 1,000 J → carnivores get 100 J → top carnivores 10 J |
| Grazing food chain | Starts with green plants (producers) → herbivores → carnivores | Most common in terrestrial ecosystems |
| Detritus food chain | Starts with dead organic matter (detritus) → decomposers → detritivores | Dominant in forest floor, deep ocean; decomposers recycle nutrients |
| Standing crop | Total biomass of living organisms at a given trophic level at a given time | Measured as biomass (dry weight per unit area) or number per unit area |
| Gross production | Total amount of energy/biomass produced at a trophic level | GPP for producers; includes energy used in respiration |
| Issue | Causes | Effects | Control Measures |
|---|---|---|---|
| Air pollution | Vehicular exhaust, industries, power plants, burning waste | CO, SO₂, NOₓ, particulates; smog; acid rain; respiratory diseases; global warming | Catalytic converters, CNG vehicles, electrostatic precipitators, scrubbers |
| Water pollution | Sewage, industrial effluents, agricultural runoff, oil spills, eutrophication | BOD increase, DO decrease; biomagnification (DDT, mercury); aquatic death; disease | Sewage treatment (primary, secondary, tertiary); bioremediation; effluent standards |
| Soil pollution | Pesticides, fertilizers, industrial waste, plastic, nuclear waste | Reduced fertility, toxic crop uptake, groundwater contamination | Organic farming, biodegradable materials, waste segregation, bioremediation |
| Global warming | CO₂, CH₄, N₂O, CFCs (greenhouse gases) trap infrared radiation | Rising temperatures, melting glaciers, rising sea level, extreme weather, coral bleaching | Reduce GHG emissions, afforestation, renewable energy, Kyoto Protocol, Paris Agreement |
| Ozone depletion | CFCs (chlorofluorocarbons), halons release Cl radicals that catalyze O₃ destruction | UV-B radiation increase → skin cancer, cataracts, reduced crop yield, phytoplankton death | Montreal Protocol (1987) — phase out CFCs; use HCFCs, HFCs instead |
| Deforestation | Logging, agriculture, urbanization, mining | Loss of biodiversity, soil erosion, disruption of water cycle, increased CO₂ | Afforestation, social forestry, agroforestry, sustainable logging, wildlife protection laws |
| Solid waste | Urban garbage, plastic, e-waste, biomedical waste | Land/water pollution, disease vectors, methane from landfills | Reduce, Reuse, Recycle (3R); composting; landfill engineering; e-waste management |
Bhopal Gas Tragedy (1984) — Methyl isocyanate (MIC) leak from Union Carbide pesticide plant; 4000+ immediate deaths, lakhs affected. (2) Chernobyl (1986) — Nuclear reactor explosion in Ukraine; massive radiation release; 31 immediate deaths; long-term ecological damage. (3) Minamata (Japan) — Mercury in industrial wastewater → biomagnified in fish → Minamata disease (neurological).Shannon Index for biodiversity: H' = −Σ(pi × ln pi). (2) Population growth rate: r = (b − d) + (i − e); where b = birth rate, d = death rate, i = immigration, e = emigration. (3) 10% Law: Energy at T(n+1) = 10% × Energy at T(n). (4) Hardy-Weinberg: p² + 2pq + q² = 1; p + q = 1.| Tool | Description | Function | Example |
|---|---|---|---|
| Restriction enzymes | Molecular scissors; cut DNA at specific palindromic sequences | Cut DNA into fragments; create sticky ends or blunt ends | EcoRI recognizes GAATTC; HindIII recognizes AAGCTT |
| DNA ligase | Molecular glue; joins DNA fragments by forming phosphodiester bonds | Seals nicks in DNA backbone; joins insert to vector | T4 DNA ligase (most commonly used) |
| Vectors | DNA molecules that carry foreign DNA into host cells | Cloning vectors (plasmid, bacteriophage), expression vectors, shuttle vectors | pBR322 (plasmid), λ phage, Ti plasmid (Agrobacterium tumefaciens) |
| Plasmid | Small circular extrachromosomal DNA in bacteria; self-replicating | Carries foreign gene; has origin of replication (ori), selectable marker (antibiotic resistance) | pBR322 has ori, ampR, tetR genes; multiple cloning site (MCS) |
| Competent host cells | Cells that can take up foreign DNA (made competent by CaCl₂ / heat shock / electroporation) | Express the foreign gene; produce recombinant protein | E. coli (most common), Bacillus, Yeast, Mammalian cells |
| PCR (Polymerase Chain Reaction) | In vitro DNA amplification; requires template, primers, Taq polymerase, dNTPs | Amplify specific DNA segment exponentially; 2ⁿ copies after n cycles | 30 cycles → ~1 billion copies; used in diagnostics, forensics, cloning |
lacZ gene within MCS. When insert is ligated into MCS, lacZ is disrupted → colonies cannot hydrolyze X-gal → white colonies (recombinant). Colonies without insert → functional lacZ → hydrolyzes X-gal → blue colonies (non-recombinant). IPTG is the inducer for lac promoter.| Application | Description | Key Details |
|---|---|---|
| Bt Cotton | Transgenic cotton with cry gene from Bacillus thuringiensis | Cry protein toxic to bollworm (lepidopteran pests); not harmful to humans; reduces pesticide use |
| Bt Toxin genes | cry1Ac (lepidopteran), cry2Ab (lepidopteran), cry1Ab (corn borer) | Toxin forms pores in insect gut → lysis → death; insect must eat Bt plant tissue |
| Recombinant Insulin | Human insulin from E. coli (Humulin); Eli Lilly (1983) | A chain and B chain produced separately in E. coli; joined by disulfide bonds; replaced animal pancreas extraction |
| Gene therapy | Replace/repair defective gene to treat genetic disorders | SCID (Adenosine deaminase deficiency) — first approved gene therapy trial (1990); retroviral vector delivers ADA gene |
| Molecular diagnosis | PCR-based detection of pathogens; nucleic acid probes; ELISA | PCR for HIV detection, Mycobacterium tuberculosis; ELISA for HIV antibodies, hepatitis; Western blotting confirmation |
| ELISA | Enzyme-Linked Immunosorbent Assay; antigen-antibody reaction with enzyme label | Direct/indirect ELISA; widely used for HIV, COVID-19, pregnancy tests; color change indicates positive result |
| Transgenic animals | Animals with foreign gene for research/production | Rosie the transgenic cow (human α-lactalbumin in milk — nutritionally superior); gene knockout mice |
| Biopesticides | Bt (Bacillus thuringiensis) toxins; Trichoderma (biocontrol fungus); NPV (Nuclear Polyhedrosis Virus) | Bt sprays on crops; Trichoderma controls fungal diseases; eco-friendly alternatives to chemical pesticides |
| Term | Definition |
|---|---|
| Cell | Basic structural and functional unit of life; smallest unit capable of independent existence |
| Cell wall | Rigid outer covering in plant cells, fungi, bacteria; provides shape and protection |
| Plasma membrane | Thin, flexible, selectively permeable barrier around cell; phospholipid bilayer with proteins |
| Protoplast | Cell without cell wall; includes plasma membrane and everything inside |
| Tonoplast | Membrane surrounding the vacuole; regulates movement of substances in/out of vacuole |
| Karyotype | Arrangement of chromosomes in pairs by size and shape; used to identify chromosomal abnormalities |
| Cytokinesis | Division of cytoplasm after nuclear division; animal = cleavage furrow, plant = cell plate |
| Plasmolysis | Shrinking of protoplast away from cell wall when cell is placed in hypertonic solution |
| Deplasmolysis | Return of protoplast to normal position when plasmolysed cell is placed in hypotonic solution |
| Turgor pressure | Pressure exerted by water inside cell against cell wall; keeps plant cells turgid |
| Osmotic pressure | Minimum pressure needed to prevent osmosis; increases with solute concentration |
| Chromatin | Loosely organized DNA + histone proteins; condenses to form chromosomes during cell division |
| Centromere / Kinetochore | Point where two sister chromatids join; kinetochore = protein structure at centromere for spindle attachment |
| Histones | Basic proteins (H1, H2A, H2B, H3, H4) around which DNA wraps to form nucleosomes |
| Nucleosome | Unit of chromatin packaging: DNA wrapped around histone octamer (2× H2A, H2B, H3, H4) |
| Active site | Specific region of enzyme where substrate binds and catalysis occurs; determines enzyme specificity |
| Denaturation | Loss of 3D structure of protein/enzyme due to heat, pH, chemicals; leads to loss of activity |
| Coenzyme | Non-protein organic molecule required for enzyme activity; loosely bound; e.g., NAD⁺, FAD |
| Prosthetic group | Tightly bound non-protein component of conjugated enzyme; e.g., heme in hemoglobin |
| Term | Definition |
|---|---|
| Gene | Unit of heredity; segment of DNA that codes for a specific polypeptide or functional RNA |
| Allele | Alternative form of a gene; occupies same locus on homologous chromosomes |
| Homozygous | Having two identical alleles for a gene (TT or tt) |
| Heterozygous | Having two different alleles for a gene (Tt) |
| Phenotype | Observable/physical expression of genes (e.g., Tall, Dwarf) |
| Genotype | Genetic constitution of an organism (e.g., TT, Tt, tt) |
| Dominant allele | Allele that expresses itself in both homozygous and heterozygous conditions |
| Recessive allele | Allele that expresses itself only in homozygous condition (masked in heterozygote) |
| Test cross | Cross between F1 individual and homozygous recessive parent to determine F1 genotype |
| Back cross | Cross between F1 and either of its parents |
| Reciprocal cross | Cross with sexes reversed compared to original cross |
| Penetrance | Percentage of individuals with a genotype who actually show the expected phenotype |
| Expressivity | Degree or intensity with which a particular genotype is expressed in the phenotype |
| Punnett square | Grid diagram used to predict genotypes and phenotypes of offspring from a cross |
| Linkage group | All genes located on the same chromosome; inherited together unless separated by crossing over |
| Chiasma | X-shaped structure visible during diplotene of Prophase I; site of crossing over |
| Recombination | New combination of genes/alleles resulting from crossing over or independent assortment |
| Centimorgan (cM) | Unit of genetic map distance; 1% recombination frequency = 1 cM |
| Autosome | Any chromosome other than sex chromosomes; humans have 22 pairs of autosomes |
| Haploid (n) | Cell with single set of chromosomes (gametes); half the diploid number |
| Diploid (2n) | Cell with two complete sets of chromosomes (somatic cells) |
| Polyploid | Having more than two complete sets of chromosomes (3n, 4n, etc.); common in plants |
| Aneuploid | Abnormal number of individual chromosomes (not complete set); e.g., Trisomy 21 (Down syndrome) |
| Frameshift mutation | Insertion or deletion of nucleotides (not in multiples of 3) that shifts reading frame |
| Point mutation | Change in a single nucleotide base; can be missense, nonsense, or silent |
| Tautomerism | Rare structural change in bases causing mispairing during DNA replication (Watson-Crick) |
| Operon | Cluster of genes under control of single promoter; functional unit of gene expression in prokaryotes |
| Inducer | Molecule that binds repressor and inactivates it, allowing transcription (e.g., allolactose for lac operon) |
| Repressor | Protein that binds operator and blocks transcription (e.g., lac repressor, trp repressor) |
| Operator | DNA sequence where repressor binds; controls access of RNA polymerase to structural genes |
| Promoter | DNA sequence where RNA polymerase binds to initiate transcription |
| Enhancer | Distant regulatory DNA sequence that increases transcription rate; position/direction independent |
| Intron | Non-coding sequence within a gene; removed by splicing during mRNA processing |
| Exon | Coding sequence within a gene; retained in mature mRNA after splicing |
| Spliceosome | Complex of snRNA and proteins that removes introns and joins exons during RNA splicing |
| Poly-A tail | Sequence of adenine nucleotides (~200) added to 3' end of mRNA; stabilizes mRNA |
| 5' cap | 7-methylguanosine cap added to 5' end of mRNA; protects from degradation, aids ribosome binding |
| VNTR | Variable Number Tandem Repeats — short repetitive DNA sequences; varies between individuals; basis of DNA fingerprinting |
| SNP | Single Nucleotide Polymorphism — variation at a single nucleotide position; most common type of genetic variation |
| Epigenetics | Study of heritable changes in gene expression without changes in DNA sequence; e.g., DNA methylation, histone modification |
| Term | Definition |
|---|---|
| Evolution | Gradual change in heritable characteristics of a population over successive generations |
| Adaptive radiation | Divergent evolution from a common ancestor into many species adapted to different niches |
| Convergent evolution | Unrelated species evolve similar traits independently due to similar environmental pressures (analogous structures) |
| Divergent evolution | Related species evolve different traits; homologous structures with different functions |
| Speciation | Formation of new species; requires reproductive isolation |
| Gene pool | Total collection of all genes and alleles in a population at a given time |
| Genetic drift | Random change in allele frequencies in small populations; bottleneck effect, founder effect |
| Founder effect | When a small group establishes a new population; allele frequencies differ from original population |
| Bottleneck effect | Sharp reduction in population size due to disaster; reduces genetic diversity |
| Gene flow | Movement of genes between populations through migration of individuals or gametes |
| Stabilizing selection | Natural selection favoring intermediate phenotypes; reduces variation |
| Directional selection | Selection favoring one extreme phenotype; shifts population mean |
| Disruptive selection | Selection favoring both extremes over intermediate; can lead to speciation |
| Fitness | Relative reproductive success of a genotype; measured by number of offspring that survive to reproduce |
| Homologous structures | Similar in structure and origin but different in function; evidence of common ancestry |
| Analogous structures | Similar in function but different in structure and origin; convergent evolution |
| Vestigial organs | Remnants of organs that were functional in ancestors but have lost function in descendants |
| Fossil | Preserved remains or traces of organisms from the past; found in sedimentary rock |
| Ecosystem | Functional unit of nature where organisms interact with each other and their physical environment |
| Biomagnification | Progressive increase in concentration of toxic substances at each trophic level |
| Eutrophication | Nutrient enrichment of water bodies (N, P) → algal bloom → O₂ depletion → aquatic death |
| Biome | Large geographic area with characteristic climate and flora/fauna (e.g., tropical rainforest, tundra) |
| Ecotone | Transition zone between two ecosystems; has higher species diversity (edge effect) |
| Keystone species | Species whose removal significantly alters ecosystem structure; e.g., sea otter, beaver, top predator |
| Carrying capacity (K) | Maximum population size that an environment can sustain indefinitely |
| Biodiversity hotspots | Areas with high species richness and high threat level; ≥1500 endemic plant species, ≥70% habitat lost |
| Red Data Book | IUCN catalogue of species facing risk of extinction |
| Gene bank | Facility that stores genetic material (seeds, sperm, eggs, tissue) for conservation |
| Ecological succession | Gradual and predictable change in species composition of a community over time |
| Pioneer species | First organisms to colonize bare/lifeless area in primary succession (lichens, mosses) |
| Climax community | Stable, self-sustaining, final community in a succession; does not change significantly |
| Biotic potential | Maximum reproductive capacity of an organism under optimal conditions |
| Term | Definition |
|---|---|
| Metabolism | Sum of all chemical reactions (anabolism + catabolism) occurring in living organisms |
| Homeostasis | Maintenance of constant internal environment (temperature, pH, blood glucose, etc.) |
| Enzyme specificity | Each enzyme acts on a specific substrate(s); determined by active site conformation |
| Coagulation | Process of blood clotting; involves clotting factors, thromboplastin, thrombin, fibrinogen → fibrin |
| Antigen | Foreign substance that triggers immune response and binds to antibodies |
| Antibody | Protein (immunoglobulin, Ig) produced by B-lymphocytes in response to antigen; Y-shaped |
| Hypertension | Persistently elevated blood pressure (>140/90 mmHg); risk factor for heart disease, stroke |
| Atherosclerosis | Deposition of cholesterol, fat on inner walls of arteries; narrows lumen → reduced blood flow |
| Glomerular Filtration Rate (GFR) | Volume of filtrate formed per minute by both kidneys; normal ≈ 125 mL/min |
| ADH (Antidiuretic Hormone) | Secreted by posterior pituitary; increases water reabsorption in DCT and collecting duct; reduces urine volume |
| Aldosterone | Mineralocorticoid from adrenal cortex; increases Na⁺ reabsorption and K⁺ excretion in DCT |
| Renin-angiotensin system | Low BP → kidneys release renin → angiotensin I → angiotensin II → vasoconstriction + aldosterone release |
| Myasthenia gravis | Autoimmune disease; antibodies destroy acetylcholine receptors at neuromuscular junction → muscle weakness |
| Multiple sclerosis | Autoimmune disease; destruction of myelin sheath in CNS → impaired nerve conduction |
| Parkinson's disease | Degenerative disorder; deficiency of dopamine in basal ganglia → tremors, rigidity, slow movement |
| Reflex action | Rapid, automatic, involuntary response to stimulus; mediated by spinal cord (no brain involvement) |
| Synapse | Junction between two neurons; electrical impulse converted to chemical signal (neurotransmitter) |
| Neurotransmitter | Chemical messenger released at synapse (ACh, dopamine, serotonin, GABA, noradrenaline) |
| Pacemaker (SA node) | Specialized cardiac muscle tissue in right atrium that initiates each heartbeat |
| Erythropoiesis | Process of RBC formation; occurs in red bone marrow; controlled by erythropoietin (EPO) from kidney |
| Haemopoiesis | Formation of all blood cells from pluripotent stem cells in bone marrow |
| Chyme | Semi-fluid, acidic mixture of partially digested food in stomach; passes to duodenum |
| Bolus | Soft, rounded mass of chewed food mixed with saliva; passes through oesophagus by peristalsis |
| Peristalsis | Rhythmic wave of contraction and relaxation of smooth muscle in GI tract; moves food forward |
| Villi | Finger-like projections in small intestine; increase surface area for absorption |
| Oxygen dissociation curve | Sigmoid curve showing relationship between pO₂ and % saturation of Hb with O₂ |
| Oxygen debt | Amount of O₂ needed to oxidize accumulated lactic acid after strenuous exercise |
| Term | Definition |
|---|---|
| Transpiration | Loss of water vapour from aerial parts of plant (mainly through stomata); ~97-99% of water absorbed |
| Guttation | Loss of liquid water through hydathodes at leaf margins/tips; occurs when root pressure is high and transpiration is low |
| Translocation | Transport of organic food (sucrose) from leaves to other parts via phloem; pressure flow hypothesis (Munch, 1930) |
| Photophosphorylation | Synthesis of ATP from ADP + Pi in chloroplast using light energy; can be cyclic or non-cyclic |
| Photorespiration | Oxidation of RuBP by O₂ (instead of CO₂) in presence of light; catalyzed by RuBisCO; releases CO₂ without producing ATP or sugar; wasteful process |
| RuBisCO | Ribulose-1,5-bisphosphate carboxylase/oxygenase; most abundant protein on Earth; catalyzes both CO₂ fixation and O₂ binding |
| Dark reaction | Light-independent reactions of photosynthesis (Calvin cycle); occurs in stroma; uses ATP and NADPH from light reaction |
| Apical dominance | Inhibition of lateral bud growth by auxin produced by apical bud; removal of apex → lateral buds grow |
| Parthenocarpy | Formation of fruit without fertilization (seedless fruit); can be induced by auxin/gibberellin application |
| Seed dormancy | Inactive state of seed; failure to germinate even under favorable conditions; broken by scarification, stratification, GA treatment |
| Senescence | Aging and eventual death of plant parts or whole plant; promoted by ethylene and ABA; delayed by cytokinins |
| Thigmomorphogenesis | Plant growth response to mechanical stimulation (touch, wind); e.g., thicker stems in windy areas |
| Phototropism | Growth movement of plant in response to light; auxin-mediated; shoots grow toward light, roots away |
| Geotropism (Gravitropism) | Growth response to gravity; roots positive geotropic (grow downward), shoots negative geotropic (grow upward) |
| Hydrotropism | Growth response to water; roots grow toward water source |
| Nitrification | Biological oxidation of NH₃ → NO₂⁻ (Nitrosomonas) → NO₃⁻ (Nitrobacter); makes nitrogen available to plants |
| Denitrification | Reduction of NO₃⁻ → N₂ / N₂O by Pseudomonas; returns nitrogen to atmosphere; reduces soil fertility |
| Nitrogen fixation | Conversion of atmospheric N₂ to NH₃; biological (Rhizobium, Azotobacter — nitrogenase enzyme) or atmospheric (lightning) or industrial (Haber process) |
| Bioremediation | Use of microorganisms to degrade/remove environmental pollutants (oil spills, heavy metals, pesticides) |
| Biopiracy | Unauthorized commercial use of bioresources and traditional knowledge of developing countries by corporations |
| Golden rice | Transgenic rice engineered with beta-carotene (provitamin A) genes; developed to combat vitamin A deficiency |
| Flavr Savr tomato | First genetically modified food product (1994); delayed ripening by antisense RNA against polygalacturonase enzyme |
| Ti plasmid | Tumour-inducing plasmid from Agrobacterium tumefaciens; used as vector for gene transfer in plants |
| Selectable marker | Gene that helps select transformed cells (e.g., antibiotic resistance ampR, nptII — neomycin/kanamycin) |
| Reporter gene | Gene that produces easily detectable product to confirm gene expression (e.g., GFP — green fluorescent protein, lacZ) |
| cDNA (complementary DNA) | DNA synthesized from mRNA template by reverse transcriptase; contains only exons (no introns); used in gene cloning and expression |
| Probes | Short, single-stranded DNA/RNA fragments complementary to target sequence; used for detection (labelled with radioactive/fluorescent tag) |
| Restriction fragment length polymorphism (RFLP) | Variation in DNA fragment lengths produced by restriction enzyme digestion; used in genetic mapping and DNA fingerprinting |
| Clonal selection | Production of identical copies of a gene/cell/organism; used in plant tissue culture, animal cloning |
| Totipotency | Ability of a single cell to develop into a complete organism; exploited in plant tissue culture (Somatic embryogenesis) |
| Term | Definition |
|---|---|
| Oogenesis | Process of ovum (egg) formation in ovary; produces one ovum and 2-3 polar bodies from one oogonium (meiosis + cytoplasmic asymmetry) |
| Spermatogenesis | Process of sperm formation in seminiferous tubules of testis; one spermatogonium → 4 spermatozoa (meiosis) |
| Fertilization | Fusion of male and female gametes to form zygote (2n); restores diploid chromosome number |
| Cleavage | Rapid mitotic divisions of zygote without growth; forms morula (solid ball of cells) → blastocyst (hollow with trophoblast and inner cell mass) |
| Implantation | Attachment of blastocyst to uterine endometrium (~day 7 after fertilization); trophoblast invades endometrium |
| Placenta | Organ connecting foetus to uterine wall; facilitates nutrient/gas/waste exchange; produces hCG, progesterone, estrogen, hPL |
| Gastrulation | Formation of three germ layers (ectoderm, mesoderm, endoderm) from blastocyst; establishes body plan |
| Organogenesis | Formation of specific organs and tissues from the three germ layers during embryonic development |
| Gestation period | Duration of pregnancy from implantation to birth; human = ~9 months (~280 days); divided into 3 trimesters |
| Lactation | Production and secretion of milk by mammary glands after childbirth; prolactin stimulates milk production, oxytocin stimulates milk ejection |
| Gametogenesis | Formation of gametes (sperm and ovum) through meiosis; ensures haploid chromosome number for sexual reproduction |