UPMSP Intermediate Biology flashcards

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

Binary fission

Asexual reproduction in which one parent cell divides into two identical daughter cells, as in Amoeba and bacteria; it is the simplest mode of asexual reproduction.

Double fertilisation

In angiosperms, one male gamete fuses with the egg to form the diploid zygote, and the second fuses with two polar nuclei to form the triploid endosperm nucleus.

Embryo sac

The female gametophyte of a flowering plant, typically 8-nucleate and 7-celled, containing the egg, two synergids, three antipodals, and a central cell with two polar nuclei.

Corpus luteum

A temporary gland formed from the ruptured follicle after ovulation; it secretes progesterone, which maintains the endometrium and supports early pregnancy.

hCG

Human chorionic gonadotropin, a hormone secreted by the developing placenta; it maintains the corpus luteum and is the molecule detected by home pregnancy tests.

Law of segregation

Mendel's principle that the two alleles of a gene separate during gamete formation, so each gamete receives only one allele of each pair.

Codominance

A condition in which both alleles are fully expressed in the heterozygote, as in AB blood group, where I^A and I^B alleles are both visible.

Linkage

The tendency of genes located close together on the same chromosome to be inherited together, reducing the frequency of recombinant offspring below independent assortment expectations.

Hardy–Weinberg equilibrium

In an ideal, non-evolving population, allele frequencies remain constant across generations, so genotype frequencies are p², 2pq, and q² for two alleles.

Down syndrome

A chromosomal disorder caused by an extra copy of chromosome 21 (trisomy 21), giving 47 chromosomes and features such as intellectual disability and a characteristic facial appearance.

Malaria

A disease caused by Plasmodium species, transmitted by the bite of an infected female Anopheles mosquito, producing cycles of fever and chills as parasites destroy red blood cells.

Secondary immune response

A rapid, strong antibody response on second exposure to an antigen, produced by memory B and T cells; it is the basis of long-lasting immunity after vaccination.

Colostrum

The first milk secreted after childbirth, rich in antibodies, especially IgA, which gives the newborn passive immunity against infections.

Biofortification

Breeding crops to increase their content of vitamins and minerals, such as iron-rich pearl millet, improving nutrition without requiring supplements.

Restriction endonuclease

An enzyme that recognises a specific palindromic DNA sequence and cuts it, producing sticky or blunt ends used in recombinant DNA technology.

pBR322

A widely used cloning vector containing an origin of replication and ampicillin and tetracycline resistance genes, allowing selection of transformed bacteria.

PCR

A technique that amplifies DNA in vitro through repeated cycles of denaturation, primer annealing, and extension by Taq polymerase, doubling copies each cycle.

Bt cotton

A genetically modified cotton carrying cry genes from Bacillus thuringiensis; its toxin becomes active in the alkaline insect gut and kills bollworm larvae.

RNA interference

A gene-silencing process in which double-stranded RNA binds to complementary mRNA and prevents its translation, used to engineer nematode resistance in plants.

Logistic growth

Population growth that slows as density approaches the carrying capacity K, producing an S-shaped curve; described by dN/dt = rN(K − N)/K.

Ten percent law

The rule that only about 10% of the energy at one trophic level is transferred to the next, so food chains are short and top predators need large areas.

Ecological succession

The orderly, predictable change in species composition of a community over time, from pioneer species to a stable climax community.

Nitrogen fixation

Conversion of atmospheric N2 into ammonia by nitrogenase, carried out by symbiotic Rhizobium in root nodules and by free-living cyanobacteria such as Anabaena.

Fluid mosaic model

The description of the plasma membrane as a phospholipid bilayer with proteins embedded or attached, forming a fluid, dynamic structure that controls transport.

Mitochondrial cristae

Folds of the inner mitochondrial membrane that increase surface area for the electron transport chain and ATP synthase, where oxidative phosphorylation produces most cellular ATP.

Crossing over

Exchange of segments between homologous chromosomes during pachytene of prophase I of meiosis, producing new allele combinations and genetic variation.

Light reaction

The thylakoid reactions of photosynthesis in which water is split, oxygen is released, and ATP and NADPH are produced for the Calvin cycle.

RuBisCO

The enzyme that catalyses CO2 fixation in the Calvin cycle by attaching CO2 to ribulose bisphosphate; it is the most abundant enzyme on Earth.

Transpiration pull

The negative pressure created by water loss from leaves that draws water upward through xylem, explained together with cohesion by the cohesion-tension theory.

Apical dominance

The suppression of lateral bud growth by auxin produced in the shoot apex, which keeps the main shoot growing and is reduced by pruning.

Glomerular filtration

The pressure-driven movement of water and small solutes from blood in the glomerulus into the nephron capsule, forming the filtrate that becomes urine.

Bohr effect

The shift of the haemoglobin–oxygen dissociation curve to the right at lower pH or higher CO2, which reduces oxygen affinity and improves oxygen delivery to tissues.