Assam HS Class 11-12 Biology cheat sheet

Five-kingdom classification (Whittaker): Monera, Protista, Fungi, Plantae, Animalia - criteria are cell type (prokaryote/eukaryote), cell wall, body organisation, nutrition mode, and phylogenetic affinity.

Binomial nomenclature rules: genus and species written in Latin, italicised in print, underlined separately when handwritten, genus capitalised, species lowercase, author name abbreviated after species.

Animal tissue decision rule: epithelium covers/lines surfaces (tight junctions, no blood supply), connective tissue has abundant matrix, muscular tissue has contractile myofibrils, neural tissue conducts impulses.

Photosynthesis: light reaction in thylakoid membranes yields ATP, NADPH and O2 from water splitting; Calvin cycle (dark reaction) in stroma fixes CO2 via RuBisCO; C4 plants use PEP carboxylase and have Kranz anatomy with low photorespiration.

Respiration: glycolysis in cytoplasm (net 2 ATP, 2 NADH), Krebs cycle in mitochondrial matrix, electron transport on inner membrane; aerobic total ≈ 36–38 ATP per glucose; RQ of carbohydrate = 1, fat < 1, protein ≈ 0.9.

Human digestive enzymes: salivary amylase (starch → maltose, pH ~6.8), pepsin (protein, acidic pH ~1.8), trypsin and chymotrypsin (proteins, alkaline), lipase (fats, bile salts emulsify); absorption mainly in small intestine villi.

Cardiac cycle timing: 0.8 s total at 72 beats/min - atrial systole 0.1 s, ventricular systole 0.3 s, joint diastole 0.4 s; SA node is the pacemaker; normal ECG waves P (atrial depolarisation), QRS (ventricular depolarisation), T (ventricular repolarisation).

Mendelian genetics: law of segregation (alleles separate at meiosis I anaphase), law of independent assortment (genes on different chromosomes); test cross with recessive parent reveals genotype; incomplete dominance gives 1:2:1 phenotype ratio.

Plant water relations: water potential = solute potential + pressure potential; water moves from higher to lower water potential; plasmolysis occurs when external solution is hypertonic; stomata open when guard cells are turgid (K+ influx).

Double fertilisation in angiosperms: one male gamete fuses with egg (syngamy → 2n zygote), the second fuses with two polar nuclei (triple fusion → 3n primary endosperm nucleus); pollen tube enters via micropyle.

Human reproduction hormones: GnRH from hypothalamus → FSH and LH from anterior pituitary; LH surge triggers ovulation around day 14 of a 28-day cycle; corpus luteum secretes progesterone; hCG and hPL are placental hormones.

Mendelian deviations: linkage (genes on same chromosome, recombination frequency ∝ distance), polygenic inheritance (continuous variation, e.g. human skin colour, kernel colour in wheat), pleiotropy (one gene, many phenotypes, e.g. phenylketonuria).

Molecular basis of inheritance: DNA replication is semi-conservative (Meselson–Stahl); DNA polymerase works 5'→3'; transcription uses RNA polymerase; genetic code is triplet, degenerate, non-overlapping, comma-less; AUG is initiator and methionine codon.

Lac operon: i gene makes repressor, binds operator and blocks transcription when lactose is absent; lactose (inducer) inactivates repressor, so RNA polymerase transcribes z, y, a genes - an inducible, negatively regulated system.

Evolution evidence and mechanisms: homologous organs show common ancestry, analogous organs show convergent evolution; Hardy–Weinberg equilibrium p² + 2pq + q² = 1 holds only with no mutation, no migration, no selection, random mating, large population.

Immunity: innate (barriers, phagocytes, inflammation) versus acquired (B lymphocytes → humoral antibody response; T lymphocytes → cell-mediated); primary response is slow with low antibody titre, secondary response is fast and strong (memory cells).

Biotechnology tools: restriction endonucleases cut at palindromic recognition sites producing sticky ends; DNA ligase joins; vectors need ori, selectable marker and recognition sites; PCR steps are denaturation (~94 °C), annealing (~50–60 °C), extension (~72 °C) using Taq polymerase.

Ecology rules: population growth exponential = rN, logistic = rN(K−N)/K; energy flow is unidirectional with ~10% transfer between trophic levels; gross primary productivity minus respiration equals net primary productivity.