Karnataka II PUC Biology (KSEAB) cheat sheet

Asexual reproduction: offspring arise from a single parent without gamete fusion; modes include binary fission (Amoeba), budding (Hydra, yeast), fragmentation (Spirogyra), zoospores (algae), conidia (Penicillium), gemmules (sponges).

Vegetative propagules in plants: rhizome (ginger), tuber (potato), bulb (onion), offset (Pistia), leaf buds (Bryophyllum), runner (grass).

Juvenile phase = vegetative phase before reproductive maturity; in plants it is the period of vegetative growth; in animals it is the pre-reproductive period.

Oestrus cycle occurs in non-primate mammals; menstrual cycle occurs in primates including humans; both are cyclic changes in the reproductive tract.

Senescence = progressive deterioration of body functions with age; in plants it may be whole-plant (monocarpic) or organ-level (leaf fall).

Types of asexual reproduction in animals: binary fission (Amoeba), budding (Hydra), fragmentation (planaria), gemmule formation (sponges), regeneration (starfish).

Water is the medium for gamete transfer in most aquatic organisms; land plants use pollen tubes; land animals use copulation/internal fertilisation.

External fertilisation occurs in bony fishes and amphibians; it requires synchronous gamete release and large numbers of gametes; internal fertilisation is typical of reptiles, birds, mammals.

Parthenogenesis = development of an unfertilised egg into an offspring; seen in rotifers, honeybees (drones), some lizards and birds.

Microsporangium wall layers (outer to inner): epidermis, endothecium, middle layers, tapetum; tapetum nourishes developing pollen.

Microsporogenesis: microspore mother cell (2n) → meiosis → microspore tetrad → each microspore → pollen grain (2-celled at shed in most angiosperms: vegetative cell + generative cell).

Megasporogenesis: megaspore mother cell (2n) → meiosis → four megaspores; usually only the chalazal one survives and forms the embryo sac.

Monosporic embryo sac (Polygonum type): 8 nuclei, 7 cells - 3 antipodals, 2 synergids, 1 egg, 1 central cell with 2 polar nuclei.

Double fertilisation: one male gamete fuses with egg → zygote (2n); the other fuses with two polar nuclei → primary endosperm nucleus (3n).

Endosperm types: free-nuclear (early coconut water) and cellular (coconut kernel); endosperm may be consumed (pea, groundnut) or persist (castor, coconut).

Perisperm = persistent nucellus (black pepper, beet); it is diploid and distinct from endosperm.

Apomixis = seed formation without fertilisation (e.g., some Asteraceae, grasses); polyembryony = more than one embryo per seed (citrus, mango).

Pollination agents and adaptations: wind (light pollen, exposed stigma), water (Zostera, Vallisneria), insects (colour, scent, nectar), birds, bats; cleistogamy ensures self-pollination.

False fruit: thalamus contributes to fruit (apple, strawberry, cashew); true fruit develops only from ovary (mango, coconut).

Spermatogenesis: spermatogonium (2n) → primary spermatocyte (2n) → meiosis I → two secondary spermatocytes (n) → meiosis II → four spermatids → spermiogenesis → spermatozoa; controlled by FSH and testosterone.

Oogenesis: oogonium (2n) → primary oocyte (2n) arrested in prophase I → at puberty completes meiosis I → secondary oocyte (n) + first polar body → meiosis II completed only after fertilisation.

Menstrual cycle: menstrual phase (days 1–5), follicular/proliferative (6–13), ovulation (~day 14, LH surge), luteal/secretory (15–28); corpus luteum secretes progesterone.

Hormonal control: GnRH from hypothalamus → FSH and LH from anterior pituitary → estrogen and progesterone from ovary; negative and positive feedback regulate the cycle.

Fertilisation occurs in the ampullary–isthmic junction of the fallopian tube; the sperm acrosome releases enzymes to penetrate the zona pellucida.

Implantation: blastocyst attaches to endometrium about 7 days after fertilisation; trophoblast secretes hCG, which maintains the corpus luteum.

Placenta hormones: hCG, hPL, estrogen, progesterone, and relaxin; hCG is the basis of pregnancy tests.

Contraceptive methods: barrier (condom, diaphragm), hormonal (pills, patches, injections), IUDs (CuT, LNG-20), surgical (vasectomy, tubectomy), emergency contraception.

Reproductive health includes ART: IVF-ET, ZIFT, GIFT, ICSI, and surrogacy; amniocentesis is used for prenatal diagnosis but is illegal for sex determination in India.

Mendel's laws: dominance, segregation (alleles separate during gamete formation), independent assortment (genes on different chromosomes assort independently).

Test cross: cross an individual of unknown genotype with a homozygous recessive; a 1:1 ratio indicates heterozygosity.

Incomplete dominance: heterozygote shows intermediate phenotype (Snapdragon flower colour); codominance: both alleles expressed (AB blood group).

Multiple alleles: ABO blood group has three alleles (IA, IB, i); a single person has only two.

Sex-linked inheritance: X-linked recessive disorders (haemophilia, colour blindness) appear more often in males; affected father cannot pass X-linked allele to sons.

Linkage and recombination: linked genes on the same chromosome tend to be inherited together; recombination frequency reflects distance (Sturtevant).

Hardy–Weinberg equilibrium: p² + 2pq + q² = 1; allele frequencies remain constant in a large, random-mating population without selection, mutation, migration, or drift.

Evidences for evolution: fossils, comparative anatomy (homologous vs analogous organs), embryology, molecular homology (DNA, proteins), biogeography.

Natural selection: variation exists; heritable variants that improve survival and reproduction increase in frequency over generations.

Speciation: allopatric (geographic isolation) and sympatric (without geographic isolation); reproductive isolation is the key criterion.

Pathogen–disease pairs: Plasmodium → malaria; Wuchereria → filariasis; Ascaris → ascariasis; Entamoeba → amoebiasis; Salmonella typhi → typhoid.

Malaria control targets the vector (female Anopheles); the parasite's sexual phase occurs in the mosquito, asexual phase in humans.

Immunity: innate (non-specific, present at birth) vs acquired (specific, memory); active immunity follows infection or vaccination; passive immunity follows antibody transfer (colostrum, antiserum).

Vaccines in the national schedule include BCG (TB), DPT (diphtheria, pertussis, tetanus), polio, measles, hepatitis B; vaccines may be live attenuated or killed/subunit.

Antibiotics: produced by microbes (Penicillium → penicillin); they act on bacteria and are ineffective against viruses; misuse promotes resistance.

Plant breeding steps: collection of variability, evaluation and selection, hybridisation (crossing), selection and testing of superior recombinants, release and notification.

Green revolution: high-yielding semi-dwarf wheat and rice varieties (introduced from IRRI/CIMMYT) with irrigation and fertiliser; associated with Norman Borlaug.

Biofortification: breeding crops with higher vitamins, minerals, or protein (e.g., iron-rich bajra, vitamin A-rich carrot, Atlas 66 wheat with high protein).

Single-cell protein (SCP): protein from microbial biomass (Spirulina, Methylophilus); useful as animal feed and human supplement.

Apiculture, pisciculture, and poultry are animal husbandry practices; bee-keeping requires knowledge of bee species, hive management, and honey extraction.

Restriction enzymes (molecular scissors) cut DNA at specific palindromic recognition sequences; EcoRI cuts GAATTC, producing sticky ends.

Cloning vector requirements: origin of replication, selectable marker, restriction sites, and ability to accept insert; common vectors are plasmids and bacteriophages.

Steps in recombinant DNA technology: isolation of DNA, cutting with restriction enzymes, ligation into vector, transformation into host, selection of transformants, and expression.

Polymerase chain reaction (PCR): denaturation (~94 °C), annealing of primers (~50–60 °C), extension by Taq polymerase (~72 °C); amplifies DNA exponentially.

Gel electrophoresis separates DNA fragments by size; DNA is negatively charged and migrates toward the anode through agarose gel.

Bt cotton: Bacillus thuringiensis cry genes (cryIAc, cryIIAb) inserted into cotton; the toxin is activated in the alkaline gut of bollworm larvae.

RNA interference (RNAi): double-stranded RNA silences a specific gene; used to make tobacco resistant to nematode Meloidogyne incognita.

Human insulin (Humulin): A and B chains of insulin produced separately in E. coli and joined by disulfide bonds; Eli Lilly, 1983.

Gene therapy: correction of a genetic defect by introducing a functional gene; first clinical case was ADA (adenosine deaminase) deficiency.

Bioreactors: large-volume vessels for microbial fermentation; types include stirred-tank and air-lift; downstream processing purifies the product.

Organism–population–community–ecosystem–biome–biosphere is the ecological hierarchy; ecology studies interactions at each level.

Population growth: exponential (r-selected, unlimited resources) vs logistic (K-selected, limited resources); logistic equation includes carrying capacity K.

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

Ecological pyramids: number, biomass, and energy; energy pyramids are always upright; biomass pyramids may be inverted (ocean).

Primary productivity: gross primary productivity (GPP) minus respiration = net primary productivity (NPP); NPP is the energy available to consumers.

Nutrient cycles: gaseous (carbon, nitrogen) and sedimentary (phosphorus, sulphur); decomposition involves fragmentation, leaching, catabolism, humification, and mineralisation.

Biodiversity hotspots in India: Western Ghats, Eastern Himalayas, Indo-Burma, Sundaland; species–area relationship: log S = log C + Z log A.

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

Environmental issues: air pollution, acid rain (SO₂, NOₓ), ozone depletion by CFCs, greenhouse effect (CO₂, CH₄, N₂O, CFCs), eutrophication, biomagnification of DDT.

Joint Forest Management and the Chipko movement illustrate community participation in conservation.

Prokaryotic cell: no nucleus or membrane-bound organelles; 70S ribosomes; cell wall of peptidoglycan; genetic material is a single circular DNA.

Eukaryotic organelles: nucleus (genetic control), mitochondria (oxidative phosphorylation), chloroplast (photosynthesis), ER (protein/lipid synthesis), Golgi (packaging), lysosome (hydrolysis), peroxisome (oxidative reactions).

Fluid mosaic model of the plasma membrane: phospholipid bilayer with integral and peripheral proteins; transport may be passive (diffusion, osmosis) or active (ATP-driven pumps).

Cell cycle phases: interphase (G1, S, G2) and M phase (karyokinesis + cytokinesis); DNA replicates in S phase.

Mitosis stages: prophase (chromosome condensation), metaphase (chromosomes align at equator), anaphase (sister chromatids separate), telophase (nuclear envelope reforms).

Meiosis I: homologous chromosomes pair (synapsis), crossing over occurs in pachytene, homologues separate in anaphase I; meiosis II separates sister chromatids.

Prophase I substages: leptotene, zygotene, pachytene, diplotene, diakinesis; chiasmata are visible in diplotene.

Enzymes of DNA replication: helicase unwinds, DNA polymerase synthesises, ligase joins Okazaki fragments; replication is semi-conservative (Meselson–Stahl).

Cell theory: all organisms are composed of cells; the cell is the basic unit of life; cells arise from pre-existing cells (Virchow).

Photosynthesis: light reactions in thylakoid membranes (PSII, PSI, ATP and NADPH); Calvin cycle in stroma fixes CO₂ via RuBisCO.

C3 plants: first stable product is 3-phosphoglycerate; C4 plants: first product is oxaloacetate (PEP carboxylase), with Kranz anatomy; C4 reduces photorespiration.

Photorespiration: RuBisCO binds O₂ instead of CO₂; wasteful of energy and carbon; higher at high temperature and high O₂.

Limiting factors: Blackman's law of limiting factors; CO₂ is usually the limiting factor for photosynthesis in nature.

Plant hormones: auxin (cell elongation, apical dominance), gibberellin (stem elongation, seed germination), cytokinin (cell division), abscisic acid (stress hormone, stomatal closure), ethylene (fruit ripening).

Photoperiodism: short-day plants flower when day length is below a critical value; long-day plants flower above it; phytochrome mediates the response.

Water potential: pure water at atmospheric pressure = 0; solutes lower it; water moves from higher to lower water potential (osmosis).

Transpiration pull–cohesion–tension theory explains water ascent in xylem; root pressure contributes at night.

Mineral nutrition: macroelements (N, P, K, Ca, Mg, S) and microelements (Fe, Mn, Zn, Cu, B, Mo, Cl, Ni); deficiency causes specific symptoms.

Nitrogen fixation: symbiotic (Rhizobium in root nodules) and free-living (Azotobacter, Anabaena); nitrogenase is oxygen-sensitive.

Digestion: carbohydrates begin in mouth (salivary amylase), proteins in stomach (pepsin), fats in small intestine (lipase, bile emulsifies); absorption mainly in ileum.

Breathing: inspiration is active (diaphragm and external intercostals contract); expiration is passive; respiratory centres are in the medulla oblongata.

Gas transport: about 97% of O₂ carried by haemoglobin; CO₂ carried as bicarbonate (~70%), carbaminohaemoglobin (~23%), and dissolved (~7%).

Heart: SA node is the pacemaker; cardiac cycle includes atrial systole, ventricular systole, and joint diastole; normal rate 72 beats/min.

Blood pressure: systolic/diastolic ~120/80 mm Hg; hypertension is persistently above 140/90 mm Hg.

Nephron: filtration in glomerulus (Bowman's capsule), reabsorption in proximal tubule, loop of Henle (counter-current), distal tubule, collecting duct; urine formation = filtration + reabsorption + secretion.

Nerve impulse: resting potential about −70 mV (Na⁺/K⁺ pump); depolarisation by Na⁺ influx; repolarisation by K⁺ efflux; conduction is saltatory in myelinated axons.

Muscle contraction: sliding filament theory; Ca²⁺ binds troponin, exposing actin-binding sites; myosin heads form cross-bridges using ATP.

Endocrine glands: pituitary (master gland), thyroid (thyroxine, regulates BMR), adrenal (cortisol, adrenaline), pancreas (insulin, glucagon), gonads (sex hormones).

Homeostasis: regulation of temperature, blood glucose, water and electrolyte balance; negative feedback maintains set points.