G - Zoological Terms

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

gamete

(Gr. gamos, marriage). A mature haploid sex cell; usually, male and female gametes can be distinguished. An egg or a sperm.

gametic meiosis

Meiosis that occurs during formation of the gametes, as in humans and other metazoa.

gametocyte

(Gr. gametes, spouse, + kytos, hollow vessel). The mother cell of a gamete, that is, immature gamete.

ganglion

pl. ganglia (Gr. little tumor). An aggregation of nerve tissue containing nerve cells.

ganoid scales

(Gr. ganos, brightness). Thick, bony, rhombic scales of some primitive bony fishes; not overlapping.

gap junction

An area of tiny canals communicating the cytoplasm between two cells.

gastrodermis

(Gr. gaster, stomach, + derma, skin). Lining of the digestive cavity of cnidarians.

gastrolith

(Gr. gaster, stomach, + lithos, stone). Calcareous body in the wall of the cardiac stomach of crayfish and other Malacostraca, preceding the molt.

gastrovascular cavity

(Gr. gaster , stomach, + L. vasculum, small vessel). Body cavity in certain lower invertebrates that functions in both digestion and circulation and has a single opening serving as both mouth and anus.

gastrozooid

(Gr. gaster, stomach, + zoon, animal). The feeding polyp of a hydroid, a hydranth.

gastrula

(Gr. gaster, stomach, + L. ula, dim.). Embryonic stage, usually cap or sac shaped, with walls of two layers of cells surrounding a cavity (archenteron) with one opening (blastopore).

gastrulation

(Gr. gaster, stomach). Process by which an early metazoan embryo becomes a gastrula, acquiring first two and then three layers of cells.

gel

(jel) (from gelatin, from L. gelare, to freeze). That state of a colloidal system in which the solid particles form the continuous phase and the fluid medium the discontinuous phase.

gemmule

(L. gemma, bud, + ula, dim.). Asexual, cystlike reproductive unit in freshwater sponges; formed in summer or autumn and capable of overwintering.

gene

(Gr. genos, descent). A nucleic acid sequence (usually DNA) that encodes a functional polypeptide or RNA sequence.

gene pool

A collection of all of the alleles of all of the genes in a population.

genetic drift

Random change in allelic frequencies in a population occurring by chance. In small populations, genetic variation at a locus may be lost by chance fixation of a single allelic variant.

genome

(Gr. genos, offspring, + oma, abstract group). All the DNA in a haploid set of chromosomes (nuclear genome), organelle (mitochondrial genome, chloroplast genome) or virus (viral genome, which in some viruses consists of RNA rather than DNA).

genomics

(je-no+miks). Mapping and sequencing of genomes (= structural genomics). Functional genomics is development and application of genome or systemwide experimental approaches to assess gene function. Functional genomics uses information derived from structural genomics.

genotype

(Gr. genos, offspring, + typos, form). The genetic constitution, expressed and latent, of an organism; the total set of genes present in the cells of an organism; contrasts with phenotype.

genus

(je-nus), pl. genera (L. race). A group of related species with taxonomic rank between family and species.

germ layer

In the animal embryo, one of three basic layers (ectoderm, endoderm, mesoderm) from which the various organs and tissues arise in the multicellular animal.

germ plasm

Cell lineages giving rise to the germ cells of a multicellular organism, as distinct from the somatoplasm.

germovitellarium

(L. germen, a bud, offshoot, + vitellus, yolk). Closely associated ovary (germarium) and yolk-producing structure (vitellarium) in rotifers.

gestation

(L. gestare, to bear). The period in which offspring are carried in the uterus.

globulins

(L. globus, a globe, ball, + -ulus, ending denoting tendency). A large group of compact proteins with high molecular weight; includes immunoglobulins (antibodies).

glochidium

(Gr. glochis, point, + idion, dim.). Bivalved larval stage of freshwater mussels.

glomerulus

(L. glomus, ball). A tuft of capillaries projecting into a renal corpuscle in a kidney. Also, a small spongy mass of tissue in the proboscis of hemichordates, presumed to have an excretory function. Also, a concentration of nerve fibers situated in the olfactory bulb.

gluconeogenesis

(Gr. glykys, sweet, + neos, new, + genesis, origin). Synthesis of glucose from protein or lipid precursors.

glycogen

(Gr. glykys, sweet, + genes, produced). A polysaccharide constituting the principal form in which carbohydrate is stored in animals; animal starch.

glycolysis

(Gr. glykys, sweet, + lysis, a loosening). Enzymatic breakdown of glucose (especially) or glycogen into phosphate derivatives with release of energy.

gnathobase

(Gr. gnathos, jaw, + base). A median basic process on certain appendages in some arthropods, usually for biting or crushing food.

gnathostomes

(Gr. gnathos, jaw, + stoma, mouth). Vertebrates with jaws.

Golgi complex

(after Golgi, Italian histologist). An organelle in cells that serves as a collecting and packaging center for secretory products.

gonad

(N.L. gonas, primary sex organ). An organ that produces gametes (ovary in the female and testis in the male).

gonangium

(N.L. gonas, primary sex organ, + angeion, dim. of vessel). Reproductive zooid of hydroid colony (Cnidaria).

gonoduct

(Gr. gonos, seed, progeny, + duct). Duct leading from a gonad to the exterior.

gonopore

(Gr. gonos, seed, progeny, + poros, an opening). A genital pore found in many invertebrates.

grade

(L. gradus, step). A level of organismal complexity or adaptive zone characteristic of a group of evolutionarily related organisms.

gradualism

A component of Darwin’s evolutionary theory postulating that evolution occurs by the temporal accumulation of small, incremental changes, usually across very long periods of geological time; it opposes claims that evolution can occur by large, discontinuous or macromutational changes.

granulocytes

(L. granulus, small grain, + Gr. kytos, hollow vessel). White blood cells (neutrophils, eosinophils, and basophils) bearing “granules” (vacuoles) in their cytoplasm that stain deeply.

green gland

Excretory gland of certain Crustacea; the antennal gland.

gregarious

(L. grex, herd). Living in groups or flocks.

guanine

(Sp. from Quechua, huanu, dung). A white crystalline purine base, C5H5N5O, occurring in various animal tissues and in guano and other animal excrements.

guild

(gild) (M.E. gilde, payment, tribute). In ecology, a group of species that exploit the same class of environment in a similar way.

gynandromorph

(Gr. gyn, female, + andr, male, + morphe, form). An abnormal individual exhibiting characteristics of both sexes in different parts of the body; for example the left side of a bilateral organism may show characteristics of one sex and the right side those of the other sex.

gynocophoric canal

(Gr. gyne, woman, + pherein, to carry). Groove in male schistosomes (certain trematodes) that carries the female.

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

Support our developers

Buy Us A Coffee