CHSE Odisha Elective Biology cheat sheet

Binomial nomenclature: genus capitalized, species lowercase, both italicized; author name in roman type.

Five-kingdom system (Whittaker): Monera, Protista, Fungi, Plantae, Animalia - based on cell type, body organization, nutrition, reproduction.

Three-domain system (Woese): Bacteria, Archaea, Eukarya; Archaea differ from Bacteria in ether-linked membrane lipids and methionine initiator tRNA.

Algae: chlorophyll-bearing, thalloid, autotrophic; classes Chlorophyceae (green), Phaeophyceae (brown, fucoxanthin), Rhodophyceae (red, phycoerythrin).

Bryophytes are amphibians of the plant kingdom: gametophyte dominant, sporophyte dependent, require water for fertilization; e.g., Marchantia, Funaria.

Pteridophytes: first vascular plants, sporophyte dominant, independent gametophyte (prothallus); e.g., Selaginella, Equisetum, Pteris.

Gymnosperms: naked ovules, no ovary, wind-pollinated; Cycas has coralloid roots with cyanobacteria, Pinus has mycorrhizal roots.

Animal phyla decision rule: presence of notochord → Chordata; jointed appendages + chitin exoskeleton → Arthropoda; water vascular system → Echinodermata; cnidoblasts → Cnidaria.

Root modification vs stem modification: roots bear no nodes, buds, or leaves; presence of nodes/internodes identifies a stem (e.g., potato tuber, Opuntia phylloclade).

Aestivation types: valvate (margins just touch), twisted (one margin overlaps the next regularly), imbricate (irregular), vexillary (papilionaceous).

Placentation: marginal (pea), axile (China rose, tomato), parietal (mustard), free central (Dianthus), basal (sunflower).

Monocot vs dicot stem: monocot has scattered vascular bundles, no secondary growth, conjoint closed bundles; dicot has ring arrangement, open bundles with cambium.

Xylem: tracheids and vessels (dead, lignified) for water transport; phloem: sieve tubes and companion cells (living) for translocation; phloem loading is active.

Epithelial tissue classification by layers (simple/stratified) and cell shape (squamous, cuboidal, columnar, ciliated); tight junctions, adhering junctions, gap junctions are cell specializations.

Three muscle types: skeletal (striated, multinucleate, voluntary), smooth (non-striated, spindle-shaped, involuntary), cardiac (striated, branched, intercalated discs, involuntary).

Connective tissue matrix rule: loose (areolar, adipose), dense (tendon - collagen; ligament - elastic), specialized (cartilage, bone, blood).

Prokaryotic vs eukaryotic: prokaryotes lack a membrane-bound nucleus and organelles, have 70S ribosomes; eukaryotes have 80S ribosomes, mitochondria, ER, Golgi.

Fluid mosaic model (Singer & Nicolson): proteins float in or on a phospholipid bilayer; membrane is selectively permeable and shows lateral diffusion.

Mitochondria are semi-autonomous: own circular DNA, 70S ribosomes, double membrane with cristae; site of Krebs cycle (matrix) and oxidative phosphorylation (inner membrane).

Cell cycle: G1 → S (DNA replication) → G2 → M; interphase occupies ~95% of cycle; checkpoints at G1/S and G2/M control entry.

Meiosis I is reductional (homologous chromosomes separate); crossing over occurs at pachytene of prophase I; meiosis II is equational like mitosis.

Biomolecule tests: Benedict's for reducing sugars, iodine for starch, Biuret for protein, Sudan III for lipids; enzymes lower activation energy without changing equilibrium.

Enzyme kinetics: Michaelis–Menten V0 = Vmax[S]/(Km+[S]); Km is the substrate concentration at half Vmax and inversely reflects affinity.

Protein structure levels: primary (sequence), secondary (α-helix, β-sheet via H-bonds), tertiary (3D folding), quaternary (multiple polypeptide subunits).

Water potential ψ = ψs (solute) + ψp (pressure); water moves from higher (less negative) to lower ψ; pure water at atmospheric pressure has ψ = 0.

Transpiration pull–cohesion–tension theory explains ascent of sap in xylem; root pressure causes guttation and is insufficient for tall trees.

Photosynthesis: light reactions in thylakoid membranes produce ATP and NADPH; Calvin cycle in stroma fixes CO2 via RuBisCO.

C3 vs C4: C4 plants (maize, sugarcane) use PEP carboxylase, have Kranz anatomy and low photorespiration; C3 plants use RuBisCO for initial fixation.

Limiting factors (Blackman): rate is set by the factor in shortest supply; light, CO2, temperature, and water commonly limit photosynthesis.

Glycolysis: glucose → 2 pyruvate, net 2 ATP, 2 NADH, in cytoplasm; Krebs cycle yields 6 NADH, 2 FADH2, 2 ATP per glucose; ETC yields ~26–28 ATP.

Photorespiration occurs when RuBisCO binds O2 instead of CO2; wasteful of carbon and energy; favored by high O2, low CO2, high temperature.

Plant hormones: auxin (apical dominance, phototropism), gibberellin (stem elongation, seed germination), cytokinin (cell division), ABA (stress, stomatal closure), ethylene (ripening).

Cardiac cycle: SA node is the pacemaker; P wave = atrial depolarization, QRS = ventricular depolarization, T = ventricular repolarization; normal rate 60–100/min.

Cardiac output = heart rate × stroke volume; typical resting value ~5 L/min; blood pressure 120/80 mmHg (systolic/diastolic).

Digestion: salivary amylase (starch), pepsin (protein, acid pH), pancreatic trypsin/lipase/amylase, bile emulsifies fats; absorption mainly in small intestine villi.

Respiratory volumes: tidal ~500 mL; vital capacity = TV + IRV + ERV; residual volume cannot be exhaled; CO2 transport mostly as bicarbonate.

Nephron: filtration at glomerulus (GFR ~125 mL/min), reabsorption in PCT (glucose, amino acids), loop of Henle creates medullary osmotic gradient, secretion in DCT, water reabsorption in collecting duct under ADH.

Counter-current mechanism in loop of Henle plus vasa recta maintains the osmotic gradient for urine concentration.

Neuron: resting potential ~−70 mV from Na+/K+ pump; depolarization by Na+ influx, repolarization by K+ efflux; refractory period prevents backward conduction.

Hormone sources: insulin/glucagon (pancreatic islets), thyroxine (thyroid, iodine-dependent), cortisol (adrenal cortex), adrenaline (adrenal medulla), ADH/oxytocin (posterior pituitary).

Flower: microsporangia in anther (pollen), megasporangium in ovule; embryo sac is 7-celled, 8-nucleate; double fertilization gives zygote + primary endosperm nucleus (3n).

Pollination types: self (autogamy) vs cross (xenogamy); wind (anemophily), water (hydrophily), insect (entomophily); pollen–pistil interaction involves recognition proteins.

Apomixis and polyembryony produce seeds without fertilization; parthenocarpy produces fruit without seeds (e.g., banana).

Human spermatogenesis: spermatogonia → primary spermatocyte → meiosis → 4 sperm; occurs in seminiferous tubules under FSH and testosterone.

Oogenesis: one primary oocyte yields one ovum plus polar bodies; meiosis II completes only after sperm entry; ovulation occurs around day 14 of a 28-day cycle.

Menstrual cycle: FSH → follicle growth → estrogen → LH surge → ovulation → corpus luteum → progesterone; falling progesterone triggers menstruation.

Contraception: barrier, hormonal (pills - ovulation suppression), IUDs, surgical (vasectomy, tubectomy); lactational amenorrhea is a natural method.

Reproductive health: STIs include gonorrhea, syphilis, chlamydiasis, genital herpes, HIV, hepatitis B; amniocentesis is misused for sex determination and is illegal for that purpose in India.

Mendel's laws: dominance, segregation (alleles separate in gametes), independent assortment (unlinked genes); test cross distinguishes homozygote from heterozygote.

Monohybrid F2 ratio 3:1; dihybrid F2 ratio 9:3:3:1; deviations indicate linkage or epistasis.

Incomplete dominance (Snapdragon pink F1) gives 1:2:1; codominance (AB blood group) expresses both alleles.

Human genetics: ABO multiple alleles (IA, IB, i); sex-linked disorders (haemophilia, colour blindness) are X-linked recessive; Down syndrome is trisomy 21.

DNA structure (Watson–Crick): antiparallel double helix, A=T (2 H-bonds), G≡C (3 H-bonds), 10 bp per turn, pitch 3.4 nm.

Replication is semiconservative (Meselson–Stahl); DNA polymerase synthesizes 5'→3'; lagging strand forms Okazaki fragments.

Central dogma: DNA → RNA (transcription) → protein (translation); lac operon is inducible, trp operon repressible; genetic code is triplet, degenerate, non-overlapping.

Evolution evidence: homologous vs analogous structures, fossils, biogeography, molecular homology; natural selection (Darwin) and Hardy–Weinberg equilibrium p²+2pq+q²=1.

Pathogen–disease pairs: Plasmodium (malaria), Salmonella typhi (typhoid), Wuchereria (filariasis), Ascaris (ascariasis), HIV (AIDS), Mycobacterium tuberculosis (TB).

Immunity: innate (barriers, phagocytes) vs acquired (B and T cells); primary response is slow, secondary is rapid due to memory cells; vaccines generate memory.

Antibodies are immunoglobulins with two heavy and two light chains; colostrum provides passive immunity via IgA.

Malaria control targets the vector Anopheles; Plasmodium life cycle alternates human host and mosquito; haemozoin release causes chill and fever.

Microbes in industry: Lactobacillus for curd, Saccharomyces for bread/beer, Aspergillus for citric acid, Penicillium for penicillin, Clostridium for butyric acid.

Sewage treatment: primary (physical) and secondary (biological, activated sludge); biogas from methanogens (Methanobacterium) is a renewable fuel.

Biofertilizers: Rhizobium (legume nodules), Azospirillum, Azotobacter, Anabaena, mycorrhiza (Glomus) improve nutrient uptake.

Plant breeding: hybridization, mutation breeding (mung bean), green revolution wheat/rice varieties; SCP (Spirulina) is a protein-rich single-cell protein.

Recombinant DNA steps: isolation of DNA → restriction digestion → ligation into vector → transformation → selection → expression.

Restriction enzymes: EcoRI cuts G↓AATTC (sticky ends), HindII cuts blunt ends; sticky ends are essential for ligation.

Vectors: pBR322 (ampR, tetR), Ti plasmid of Agrobacterium for plant transformation, retroviruses for animal cells; selectable markers identify transformants.

PCR: denaturation (~94 °C), annealing (~50–60 °C), extension (~72 °C, Taq polymerase); amplifies DNA exponentially.

Gel electrophoresis separates DNA by size; DNA is negatively charged and migrates toward the anode; ethidium bromide or SYBR stains it.

Bt cotton carries cry genes (cryIAc, cryIIAb) from Bacillus thuringiensis; the toxin is activated in the alkaline insect midgut.

RNA interference (RNAi) protects against nematode Meloidogyne by silencing mRNA; used in tobacco against Meloidogyne incognita.

Gene therapy: ADA deficiency treated by inserting functional ADA gene into lymphocytes; insulin produced by recombinant E. coli chains A and B.

Population growth: exponential dN/dt = rN; logistic dN/dt = rN(K−N)/K with carrying capacity K; r is intrinsic rate of natural increase.

Species interactions: mutualism (+,+), competition (−,−), predation and parasitism (+,−), commensalism (+,0), amensalism (−,0).

Ecological pyramids: number, biomass, energy; energy pyramid is always upright; biomass pyramid can be inverted in ocean ecosystems.

Primary productivity: gross primary productivity minus respiration = net primary productivity; only ~10% of energy transfers between trophic levels.

Nutrient cycles: gaseous (carbon, nitrogen) and sedimentary (phosphorus); nitrogen fixation by Rhizobium and lightning, nitrification by Nitrosomonas/Nitrobacter.

Biodiversity hotspots in India: Western Ghats, Eastern Himalaya, Indo-Burma, Sundaland; species–area relationship S = C·A^z with z ≈ 0.1–0.2.

In situ conservation: biosphere reserves, national parks, wildlife sanctuaries; ex situ: zoos, botanical gardens, seed banks, cryopreservation.

Pollution indicators: BOD measures organic load, high BOD = polluted water; ozone depletion by CFCs; greenhouse gases include CO2, CH4, N2O, CFCs.