UPMSP Intermediate Biology cheat sheet

Asexual reproduction in Amoeba is binary fission; in Hydra it is budding; in Planaria it is regeneration; in Spirogyra it is fragmentation.

Double fertilisation: one male gamete fuses with the egg (syngamy → 2n zygote), the second with two polar nuclei (triple fusion → 3n primary endosperm nucleus).

Microsporogenesis: microspore mother cell (2n) undergoes meiosis to give four microspores, each forming a pollen grain with a generative cell and a vegetative cell.

Megasporogenesis in the ovule produces four megaspores; usually only the chalazal one survives and forms the 8-nucleate, 7-celled embryo sac.

Human spermatogenesis produces four sperm per primary spermatocyte; oogenesis produces one ovum plus three polar bodies from one primary oocyte.

Menstrual cycle: ovulation near day 14 of a 28-day cycle; LH surge triggers ovulation; corpus luteum secretes progesterone; fertilisation window is roughly 2 days before to 1 day after ovulation.

Placenta secretes human chorionic gonadotropin (hCG), which maintains the corpus luteum; hCG is the hormone detected in home pregnancy tests.

Contraceptive classification: barrier (condom, diaphragm), hormonal (oral pills, patches), intrauterine device (CuT, LNG-20), surgical sterilisation (vasectomy, tubectomy).

Mendel's laws: dominance (monohybrid F2 phenotype 3:1, genotype 1:2:1), segregation (two alleles separate in gamete formation), independent assortment (dihybrid F2 phenotype 9:3:3:1).

ABO blood groups: three alleles I^A, I^B, i; I^A and I^B codominant, i recessive; six genotypes give four phenotypes.

Sex-linked recessive inheritance: a carrier mother (X^A X^a) × unaffected father yields 50% of sons affected and 50% of daughters carriers.

Linkage reduces recombinant frequency; recombination frequency between two loci maps to distance in centimorgans (1 cM = 1% recombinants).

Hardy–Weinberg: p + q = 1 and p² + 2pq + q² = 1; allele frequencies stay constant in an ideal population, and 2pq is the carrier frequency.

Chromosomal disorders: Down syndrome trisomy 21 (47 chromosomes), Turner syndrome 45,X, Klinefelter syndrome 47,XXY.

Human evolution sequence: Homo habilis → Homo erectus → Neanderthal man → Homo sapiens; Homo sapiens arose in Africa and migrated worldwide.

Molecular evidence for evolution includes universal genetic code, homologous genes (e.g. cytochrome c), and DNA hybridisation data.

Disease–pathogen pairs: malaria–Plasmodium, amoebiasis–Entamoeba histolytica, typhoid–Salmonella typhi, tuberculosis–Mycobacterium tuberculosis, filariasis–Wuchereria bancrofti.

Malaria vector is the female Anopheles mosquito; the parasite multiplies in liver cells and then red blood cells, causing fever with chills.

Immunity: primary response is slow and antibody titre low; secondary response is fast and large due to memory B and T cells; colostrum supplies IgA to the newborn.

Vaccination uses weakened or killed pathogens or toxoids to generate memory cells; passive immunity uses ready-made antibodies (e.g. antivenom).

Animal husbandry: apiculture (bees, honey and wax), pisciculture (fish), poultry (broilers versus layers), and inbreeding versus outcrossing for hybrid vigour.

Plant breeding steps: germplasm collection → hybridisation → selection → testing and release; green revolution relied on semidwarf wheat and rice varieties.

Biofortification raises micronutrient content (e.g. iron-rich bajra, vitamin A-rich carrot) and differs from food supplementation.

Biocontrol agents: Bacillus thuringiensis against insect larvae, Trichoderma against soil fungi, ladybird and dragonfly against aphids and mosquitoes.

Recombinant DNA steps: isolate DNA → cut with restriction endonuclease (sticky ends) → ligate into vector with DNA ligase → transform host → select recombinants.

Restriction enzymes recognise palindromic sequences; EcoRI cuts GAATTC; the enzyme that cuts DNA is a nuclease, and methylase protects host DNA.

pBR322 carries ampicillin and tetracycline resistance genes; insertional inactivation of one marker allows selection of recombinants.

PCR: denaturation (~94 °C), primer annealing (~50–60 °C), extension by Taq polymerase (~72 °C); each cycle doubles the DNA, so n cycles give about 2^n copies.

Bt cotton carries cry genes from Bacillus thuringiensis; the toxin is inactive in the bacterium and becomes active in the alkaline gut of the insect.

RNA interference (RNAi) uses double-stranded RNA to silence a nematode gene; this gives resistance to Meloidogyne incognita in tobacco.

Human insulin was first produced in E. coli by inserting A and B chain genes separately, then joining the chains; earlier insulin came from slaughtered animals.

Gene therapy corrects a defect by inserting a functional gene; ADA deficiency was an early target using lymphocytes; ELISA and PCR are diagnostic tools.

Population growth: exponential is dN/dt = rN (J-shaped); logistic is dN/dt = rN(K − N)/K (S-shaped), where K is carrying capacity.

Species interactions: mutualism (+,+), commensalism (+,0), parasitism (+,−), predation (+,−), competition (−,−); mycorrhiza is mutualistic.

Energy flow follows the 10% law: only about 10% of energy transfers to the next trophic level, so food chains rarely exceed 4–5 links.

Ecological pyramids can be upright (numbers in grassland, energy), inverted (numbers in a single tree), or spindle-shaped (biomass in a pond).

Primary succession on bare rock: lichens → mosses → herbs → shrubs → trees; primary succession is slow because soil must first form.

Nutrient cycles: carbon and nitrogen are gaseous; phosphorus is sedimentary; nitrogen fixation uses nitrogenase (N2 → NH3) in Rhizobium and cyanobacteria.

Biodiversity hotspots in India include the Western Ghats, Himalaya, Indo-Burma, and Sundaland; India has about 2.4% of global land area and 8.1% of species.

Conservation: in situ (national parks, biosphere reserves) versus ex situ (zoos, seed banks, botanical gardens); the Red Data Book lists threatened species.

Prokaryotic cell lacks a nuclear membrane and membrane-bound organelles; it has a 70S ribosome, nucleoid, and often a cell wall with peptidoglycan.

Eukaryotic organelles: mitochondria (ATP, cristae, own DNA), chloroplast (photosynthesis, thylakoids, own DNA), lysosome (hydrolytic enzymes, acidic pH), Golgi (packaging and secretion).

Fluid mosaic model: the plasma membrane is a phospholipid bilayer with embedded proteins; the hydrophobic tails face inward and hydrophilic heads outward.

Mitochondrial electron transport chain complexes I–IV pump protons; ATP synthase (complex V) makes ATP; oxygen is the final electron acceptor.

Glycolysis in cytoplasm yields 2 ATP and 2 NADH per glucose; the Krebs cycle and oxidative phosphorylation in mitochondria give most ATP.

Cell cycle: interphase (G1, S, and G2) precedes mitosis; DNA replicates in S phase; mitosis has prophase, metaphase, anaphase, telophase; cytokinesis follows.

Meiosis has two divisions; crossing over occurs in prophase I (pachytene); homologous chromosomes separate in anaphase I; sister chromatids separate in anaphase II.

Enzyme kinetics: Michaelis–Menten relation v = Vmax[S]/(Km + [S]); Km is the substrate concentration at half Vmax; competitive inhibitors raise apparent Km.

Photosynthesis: light reaction in thylakoids (PSII → PSI, water split, O2 released, ATP and NADPH formed); Calvin cycle in stroma fixes CO2 via RuBisCO.

C3 plants fix CO2 into 3-PGA; C4 plants (maize, sugarcane) use PEP carboxylase and bundle-sheath cells to reduce photorespiration; CAM plants fix CO2 at night.

Chlorophyll a and b absorb mainly blue-violet and red light; green light is largely reflected, which is why leaves look green.

Transpiration pull and cohesion-tension theory explain water ascent in xylem; root pressure contributes mainly at night.

Stomatal opening: guard cells take up K+ and water, become turgid, and open the pore; ABA causes closure under water stress.

Mineral deficiency symptoms: N and Mg cause chlorosis (yellowing); Fe causes interveinal chlorosis; Ca causes tip necrosis; B causes poor pollen and fruit set.

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

Photoperiodism: short-day plants flower when night exceeds a critical length; long-day plants flower when night is shorter; phytochrome mediates the response.

Nephron: filtration in the glomerulus, reabsorption of glucose and amino acids in the proximal tubule, and water reabsorption in the loop of Henle and collecting duct under ADH control.

Blood: plasma ~55%, formed elements ~45%; erythrocytes carry O2 via haemoglobin, leucocytes defend, platelets clot; normal human RBC count about 5 million per µL.

Cardiac cycle: SA node sets the rhythm; systole and diastole; the ECG has P (atrial depolarisation), QRS (ventricular depolarisation), and T (ventricular repolarisation) waves.

Gas transport: about 97% of O2 carried as oxyhaemoglobin; CO2 carried mainly as bicarbonate; the Bohr effect shifts the dissociation curve right with lower pH.

Digestion: salivary amylase digests starch; pepsin digests protein in acid stomach; pancreatic lipase, amylase, and trypsin act in the small intestine; bile emulsifies fat.

Neuron: resting potential about −70 mV; depolarisation opens Na+ channels; repolarisation opens K+ channels; the impulse travels to the synapse, where a neurotransmitter is released.

Hormones: insulin lowers blood glucose; glucagon raises it; thyroxine controls basal metabolic rate; ADH retains water; aldosterone retains Na+.

Muscle contraction: sliding filament model; Ca2+ binds troponin, exposing actin sites; myosin heads bind actin, use ATP, and pull the filaments together.