Tamil Nadu HSE Second Year Biology flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Double fertilization

In angiosperms, one male gamete fuses with the egg to form a diploid zygote; the other fuses with two polar nuclei to form a triploid primary endosperm nucleus.

Apomixis

Asexual production of seeds without fertilization, resulting in genetically identical offspring; examples include Citrus and mango.

Menstrual cycle phases

The reproductive cycle in human females: menstrual phase (days 1–5), follicular phase (6–13), ovulation (~14), luteal phase (15–28), regulated by FSH, LH, estrogen, and progesterone.

Vegetative propagation

Asexual reproduction in plants using vegetative parts such as runners, rhizomes, tubers, bulbs, and leaf buds, producing clones.

Mendel's law of segregation

Alleles of a gene separate during gamete formation, so each gamete receives only one allele; observed in monohybrid crosses.

Incomplete dominance

A pattern where the heterozygous phenotype is intermediate between the two homozygous phenotypes, as in pink flowers of Snapdragon.

Lac operon

An inducible operon in E. coli regulated by lactose; lactose binds the repressor, allowing transcription of genes for lactose metabolism.

Hardy-Weinberg principle

In a large, randomly mating population without evolutionary forces, allele and genotype frequencies remain constant; p² + 2pq + q² = 1.

Restriction enzymes

Enzymes that recognize specific DNA sequences and cut DNA at or near those sites, producing sticky or blunt ends; used in genetic engineering.

PCR

Polymerase Chain Reaction: in vitro amplification of DNA using denaturation, annealing of primers, and extension by Taq polymerase, repeated in cycles.

Bt toxin

Insecticidal protein produced by Bacillus thuringiensis; cry genes encode it; activated in the alkaline gut of insects, causing cell lysis and death.

Gene therapy

A technique that introduces a functional gene into a patient's cells to treat a genetic disorder, such as ADA deficiency.

Ecological pyramid

A graphical representation of trophic levels showing number, biomass, or energy; energy pyramids are always upright due to the 10% law.

Eutrophication

Nutrient enrichment of water bodies causing algal blooms, oxygen depletion, and death of aquatic organisms.

Biodiversity hotspot

A region with high species richness and endemism that is under significant threat; examples include Western Ghats and Eastern Himalayas.

Biomagnification

The increase in concentration of a persistent pollutant at successive trophic levels, e.g., DDT in food chains.

Mitosis

Cell division producing two genetically identical diploid daughter cells; stages: prophase, metaphase, anaphase, telophase.

Meiosis

Reduction division producing four haploid cells; includes crossing over in prophase I, generating genetic variation.

Oxidative phosphorylation

ATP production in mitochondria via electron transport chain and chemiosmosis, using NADH and FADH2 as electron donors.

Calvin cycle

Light-independent reactions of photosynthesis where RuBisCO fixes CO2 into glucose using ATP and NADPH.

Water potential

The potential energy of water per unit volume; water moves from higher to lower water potential; Ψ = Ψs + Ψp.

Transpiration

Loss of water vapor from plant leaves through stomata, driven by transpirational pull and cohesion-tension.

Photoperiodism

Response of plants to the relative length of day and night, controlling flowering in short-day and long-day plants.

Vernalization

Promotion of flowering by exposure to cold temperature, as seen in winter wheat.

Binomial nomenclature

System of naming organisms with two Latinized names: genus and species, e.g., Homo sapiens; introduced by Linnaeus.

Five kingdom classification

Whittaker's system dividing organisms into Monera, Protista, Fungi, Plantae, and Animalia based on cell structure, nutrition, and phylogeny.

Lichen

Symbiotic association between a fungus and an alga or cyanobacterium; used as pollution indicators.

Mycorrhiza

Symbiotic association between a fungus and plant roots, enhancing nutrient and water uptake.

Active immunity

Immunity produced by the body's own immune response after exposure to an antigen, e.g., after vaccination or infection.

Biofortification

Breeding crops to increase their nutritional value, such as golden rice enriched with vitamin A.

Single Cell Protein

Protein extracted from microorganisms such as Spirulina and Methylophilus, used as a food supplement.

Sewage treatment

Process of removing contaminants from wastewater through primary (physical), secondary (biological), and tertiary (chemical) stages.