BCS Written Zoology flashcards

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

Fluid mosaic model

Description of the plasma membrane as a phospholipid bilayer with embedded proteins, cholesterol, and glycoproteins that move laterally, giving the membrane a mosaic, fluid character.

Oxidative phosphorylation

Mitochondrial process where the electron transport chain pumps protons and ATP synthase uses the resulting proton gradient to phosphorylate ADP into ATP.

Km (Michaelis constant)

Substrate concentration at which an enzyme reaches half its maximum velocity; a low Km indicates high substrate affinity of the enzyme.

Semiconservative replication

DNA replication mode in which each daughter double helix contains one original parental strand and one newly synthesized complementary strand.

Hardy-Weinberg equilibrium

Allele and genotype frequencies remain constant across generations in a large, randomly mating population without mutation, migration, or selection.

Lac operon

Inducible bacterial gene system for lactose metabolism; the repressor binds the operator unless lactose is present, while CAP-cAMP activates transcription when glucose is low.

Frameshift mutation

Insertion or deletion of nucleotides not in multiples of three, shifting the reading frame and usually producing a truncated, nonfunctional protein.

Choanocytes

Flagellated collar cells lining sponge cavities; their beating drives water flow and their collar traps food particles for intracellular digestion.

Nematocysts

Stinging organelles within cnidocytes of Cnidaria; discharge a coiled thread and toxin used for prey capture and defense.

Water vascular system

Network of canals and tube feet unique to echinoderms, used for locomotion, feeding, and gas exchange; operates hydraulically.

Biological species concept

Definition of species as groups of interbreeding natural populations that are reproductively isolated from other such groups; not applicable to asexual organisms.

Monophyletic group

A clade consisting of a common ancestor and all of its descendants; recognized by shared derived characters called synapomorphies.

Holotype

The single specimen designated by an author as the name-bearing type of a species; it anchors the application of the scientific name.

Bohr effect

Rightward shift of the hemoglobin-oxygen dissociation curve caused by low pH, high carbon dioxide, or high temperature, promoting oxygen release to tissues.

Countercurrent multiplication

Process in the loop of Henle where opposing fluid flows create an osmotic gradient, enabling concentration of urine in the collecting duct under ADH.

Negative feedback

Regulatory mechanism in which rising levels of a target hormone inhibit hypothalamic or pituitary secretion, stabilizing hormone concentrations.

Cortical reaction

Release of cortical granules after sperm entry that modifies the egg coat, blocking further sperm binding and preventing polyspermy.

Gastrulation

Embryonic process that rearranges the blastula into three germ layers: ectoderm, mesoderm, and endoderm, establishing the body plan.

Spemann organizer

Dorsal blastopore lip region in amphibians that induces surrounding tissue to form the neural axis and dorsal mesoderm during gastrulation.

Logistic growth

Population growth model dN/dt = rN(K-N)/K, where growth slows as population N approaches carrying capacity K, producing an S-shaped curve.

Competitive exclusion principle

Two species competing for the same limiting resource cannot coexist indefinitely; the superior competitor excludes the other unless niches diverge.

Keystone species

A species whose influence on community structure is disproportionately large relative to its abundance; its removal causes major ecosystem change.

Ex-situ conservation

Conservation of species outside their natural habitat, as in zoos, botanical gardens, seed banks, and cryopreservation of gametes or embryos.

Genetic drift

Random change in allele frequencies due to sampling error in finite populations; strongest in small populations and reduces genetic variation.

Allopatric speciation

Formation of new species when populations become geographically isolated, diverge genetically, and later acquire reproductive isolation.

Maximum sustainable yield

The largest catch that can be removed from a fish stock indefinitely without depleting it; theoretically occurs near half the carrying capacity.

Mark-recapture estimate

Population size estimate N = (M x C)/R, where M is marked initially, C is the second sample, and R is marked individuals recaptured.

Hypophysation

Induced breeding technique in which pituitary gland extract or synthetic hormone is injected into brood fish to trigger spawning.

Plasmodium life cycle

Sporozoites from an Anopheles bite infect liver cells, merozoites invade red blood cells causing fever, and gametocytes are taken up by mosquitoes.

Herd immunity

Indirect protection of susceptible individuals when a sufficient proportion of the population is immune, reducing pathogen transmission.

Immunoglobulin structure

Y-shaped antibody of two heavy and two light chains; variable regions bind antigen, constant regions determine class and effector function.

Restriction enzyme

Bacterial enzyme that cuts DNA at specific palindromic recognition sequences, producing sticky or blunt ends used in gene cloning.