MATSEC IM Biology flashcards

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

Semi-conservative replication

Each new DNA molecule contains one original parental strand and one newly synthesised strand, because complementary base pairing directs the addition of nucleotides during replication.

Hardy-Weinberg equation

p + q = 1 and p² + 2pq + q² = 1 describe allele and genotype frequencies in a population not evolving at a locus, where q² is the homozygous recessive frequency.

Water potential

The tendency of water to move from one place to another, measured in kPa, equal to solute potential plus pressure potential; water moves from higher to lower water potential.

Competitive inhibitor

A molecule with a shape similar to the substrate that binds the active site and blocks substrate entry, raising the substrate concentration needed to reach a given rate.

Transpiration pull

The upward movement of water through xylem driven by evaporation at the leaves, maintained by cohesion between water molecules and adhesion to xylem walls.

Cardiac output

The volume of blood pumped by one ventricle per minute, calculated as heart rate multiplied by stroke volume and increased during exercise by both factors.

Negative feedback

A control mechanism in which a detected deviation from a set point triggers an effector response that reverses the change, restoring the internal condition towards normal.

Eutrophication

Nutrient enrichment of water causing algal blooms; decomposers then deplete oxygen, killing aerobic organisms such as fish and invertebrates.

Net primary productivity

The energy or biomass fixed by producers that remains after respiratory losses, calculated as gross primary productivity minus respiration, and available to consumers.

Simpson's index of diversity

D = 1 − Σ(n/N)², where n is the number of individuals of each species and N is the total; values near 1 indicate high diversity.

Mitotic index

The proportion of cells in a sample showing visible chromosomes, calculated as dividing cells divided by total cells counted, used to compare tissue growth rates.

Osmosis

The net movement of water molecules across a partially permeable membrane from a region of higher water potential to a region of lower water potential.

Test cross

A cross between an individual showing a dominant phenotype and a homozygous recessive individual, used to reveal whether the unknown genotype is homozygous or heterozygous.

Sex-linked inheritance

Inheritance of genes located on sex chromosomes; recessive X-linked disorders appear more frequently in males because they carry only one X chromosome.

Chi-squared test

A statistical test using χ² = Σ((O − E)² ÷ E) to compare observed and expected frequencies, with degrees of freedom equal to classes minus one.

Restriction enzyme

An enzyme that cuts DNA at a specific recognition sequence, producing fragments with sticky ends used in gene cloning and DNA analysis.

Gel electrophoresis

A technique separating DNA fragments by size; negatively charged DNA moves towards the positive electrode, with smaller fragments travelling further through the gel.

Translocation in phloem

The movement of sucrose and amino acids from source to sink, driven by pressure flow generated when sucrose loading draws water into sieve tubes.

Phototropism

Growth of a plant shoot towards light caused by auxin redistribution to the shaded side, where increased cell elongation bends the shoot towards the light.

ADH action

Antidiuretic hormone increases the permeability of the collecting duct to water, so more water is reabsorbed and a smaller volume of concentrated urine is produced.

Reflex arc

The pathway of a reflex response: receptor, sensory neurone, relay neurone in the spinal cord, motor neurone and effector, producing a rapid automatic reaction.

Bohr shift

A rightward shift of the haemoglobin oxygen dissociation curve caused by higher carbon dioxide concentration, reducing affinity and releasing more oxygen to active tissues.

Antibiotic resistance

Bacteria with mutations conferring resistance survive antibiotic treatment and multiply, so resistance spreads through populations and by transfer of resistance plasmids.

Mark-recapture estimate

Population size estimated as N = (M × C) ÷ R, where M is marked initially, C is the total recaptured and R is the number recaptured that were marked.

Indicator species

An organism whose presence or abundance reveals environmental conditions, such as lichens indicating sulfur dioxide levels or mayfly larvae indicating clean water.

Herd immunity

Protection of unvaccinated individuals that arises when a high proportion of the population is immune, reducing pathogen transmission and outbreak risk.

Glycolysis

The first stage of respiration in the cytoplasm, splitting glucose into pyruvate and yielding a net gain of two ATP and two reduced NAD per glucose.

Oxidative phosphorylation

ATP synthesis on the inner mitochondrial membrane driven by a proton gradient established by the electron transport chain using reduced NAD and FAD.

Calvin cycle

The light-independent stage of photosynthesis in the stroma, where rubisco fixes carbon dioxide onto ribulose bisphosphate using ATP and reduced NADP to form triose phosphate.

Limiting factor

The factor in shortest supply that restricts the rate of a process such as photosynthesis, so increasing other factors has no effect until it is relieved.

Magnification formula

Magnification equals image size divided by actual size; both measurements must be converted to the same unit before the division is carried out.

Species definition

A group of organisms with similar characteristics that can interbreed to produce fertile offspring, forming the basic unit of classification and biodiversity.