AP Intermediate Zoology (BIEAP) key terms

The two-part scientific naming system in which each species receives a genus name followed by a species epithet, both usually Latinised and italicised, giving every organism a single internationally recognised label.

The branch of biology that identifies, describes, names and arranges organisms into hierarchical groups such as species, genus, family, order, class and phylum, providing the framework for all comparative zoology.

The single preserved individual, designated when a new species is described, that acts as the permanent reference for that name and to which later specimens are compared when identity is disputed.

Similarity of structures or genes arising from shared ancestry rather than from similar function, such as the forelimbs of bats, whales and humans, which is the primary evidence used to build phylogenetic groupings.

Structures that perform similar functions in unrelated groups but differ in embryonic origin and anatomy, such as the wings of insects and birds, showing adaptation rather than common descent.

A body cavity fully lined by mesoderm, lying between the body wall and the gut, which allows organ packing, independent gut movement and, in many animals, a hydrostatic skeleton.

A body cavity present between the body wall and gut but not completely lined by mesoderm, as in nematodes, where it is derived from the blastocoel and functions mainly in support and transport.

The division of the body into a linear series of similar segments, each with its own mesodermal coelomic compartment, seen in annelids and reflected in the segmented trunk of vertebrates.

The fusion and specialisation of groups of body segments into distinct functional units, such as the cephalothorax and abdomen of crustaceans or the head, thorax and abdomen of insects.

A stiff, dorsal, rod-like structure of vacuolated cells that runs beneath the nerve cord in chordate embryos and persists in adult lancelets and lampreys, defining the phylum Chordata.

The animal phylum defined by a notochord, dorsal hollow nerve cord, pharyngeal gill slits and a post-anal tail at some stage of life, comprising tunicates, lancelets and vertebrates.

The network of canals, ampullae and tube feet unique to echinoderms that operates hydraulically for locomotion, feeding, respiration and sensory reception, and opens to the sea through the madreporite.

Hollow, extensible projections of the echinoderm water vascular system, each with a muscular ampulla and a sucker, used for creeping locomotion, prey handling and gas exchange.

The structural and functional unit of the vertebrate kidney, consisting of a renal corpuscle and tubule, which filters blood plasma and adjusts the composition of the fluid that becomes urine.

The arrangement of the loop of Henle with descending and ascending limbs carrying fluid in opposite directions, which builds a steep osmotic gradient in the medulla and allows production of concentrated urine.

The active control of water and dissolved solute concentrations in body fluids so that cells neither swell nor shrink, achieved by excretory organs and behavioural or hormonal adjustments to the environment.

The maintenance of internal conditions such as temperature, pH and glucose concentration within narrow limits through negative feedback loops involving sensors, control centres and effectors.

A regulatory mechanism in which a deviation from a set point triggers responses that reduce that deviation, restoring stability, as in the control of blood glucose by insulin and glucagon.

A chemical messenger secreted by endocrine cells into the blood, which travels to distant target tissues and alters their activity by binding to specific receptors.

The release of hormones by neurons, as when hypothalamic cells secrete releasing factors or when the corpora cardiaca of insects release peptides into the haemolymph, linking nervous and endocrine control.

The steroid moulting hormone of arthropods, secreted by the prothoracic glands under brain and juvenile hormone control, which triggers the shedding of the old cuticle during growth and metamorphosis.

A hormonally controlled change of body form between larval and adult stages, either gradual as in hemimetabolous insects or involving a pupal stage as in holometabolous insects and most amphibians.

A free-living, sexually immature stage that differs in structure and habits from the adult, often serving for dispersal or feeding, as in tadpoles, caterpillars and trochophore larvae.

The embryonic process in which cells rearrange to form the three germ layers, ectoderm, mesoderm and endoderm, establishing the body plan and the future gut opening.

The three primary cell layers of the embryo, ectoderm, mesoderm and endoderm, whose derivatives give rise to the nervous system, muscles and skeleton, and gut lining respectively.

The stage of development in which the dorsal ectoderm folds into a neural tube above the notochord, giving rise to the brain and spinal cord, while neural crest cells migrate away.

The characteristic proportion of phenotypes among offspring of a defined cross, such as 3:1 from a monohybrid F2 or 9:3:3:1 from a dihybrid F2, expected when genes assort independently.

A cross of an individual of unknown genotype with a homozygous recessive partner, used to reveal whether the unknown carries a dominant allele and to detect recombination frequencies.

The tendency of genes located close together on the same chromosome to be inherited together, producing fewer recombinant offspring than independent assortment would predict.

The reciprocal exchange of chromosome segments between homologous chromatids during prophase I of meiosis, which breaks linkage and generates new combinations of alleles.

A cluster of bacterial genes transcribed together from one promoter, regulated by an operator and repressor or activator proteins, as in the lactose utilisation genes of Escherichia coli.

The synthesis of an RNA molecule from a DNA template by RNA polymerase, the first step of gene expression and the stage at which many regulatory controls act.

The whole process by which information in a gene is converted into a functional product, usually a protein, including transcription, RNA processing, translation and later modification.

The differential survival and reproduction of individuals differing in heritable traits, so that alleles conferring advantage in a given environment increase in frequency over generations.

The relative contribution an individual makes to the next generation's gene pool, measured as reproductive success and used to compare the adaptive value of alternative traits or genotypes.

The independent evolution of similar features in distantly related lineages exposed to comparable selection pressures, producing analogous rather than homologous structures such as streamlined bodies in fish and dolphins.

The rapid, irreversible learning that occurs during a sensitive period soon after hatching or birth, in which a young animal fixes its attention on the first moving object it sees.

An innate, stereotyped behaviour pattern performed without prior experience and triggered by a specific sign stimulus, such as the egg-rolling response of a greylag goose.

A graphical representation of numbers, biomass or energy at successive trophic levels, which is always upright for energy because transfer between levels is inefficient.

The feeding position an organism occupies in a food chain, such as producer, primary consumer or secondary consumer, determined by the number of transfer steps from the energy source.

The interconnected network of feeding relationships in a community, in which species may occupy several trophic levels and alternative prey pathways buffer the system against disturbance.

The progressive increase in concentration of a persistent fat-soluble pollutant along a food chain, reaching harmful levels in top predators such as fish-eating birds and humans.

The technique of injecting fish with pituitary extract or synthetic gonadotropin to trigger spawning on demand, widely used in carp hatcheries and developed from the work of Houssay and Chaudhuri.

Induced breeding by administering pituitary gland extract, usually from a mature donor carp, to brood fish so that they spawn in captivity outside the natural breeding season.

The rearing of several fish species with different feeding habits in the same pond, so that food available at different levels is used efficiently and total yield rises.

A bacterial enzyme that recognises a specific DNA sequence and cuts the double helix at or near it, providing the molecular scissors used in cloning and genetic engineering.

A small circular DNA molecule that replicates independently in bacteria and carries an inserted gene into host cells, usually engineered with a selectable marker and a cloning site.

A DNA molecule assembled in vitro from sequences of different origins, such as a plasmid joined to a foreign gene, forming the basis of gene cloning and transgenic technology.

An in vitro method that repeatedly denatures, anneals primers and extends them with a thermostable polymerase, doubling a target DNA sequence each cycle to yield millions of copies.