Lewis/Life - Glossary

G

G1 phase The gap stage of interphase when proteins, lipids, and carbohydrates are synthesized. 168

G2 phase The gap stage of interphase when membrane components are synthesized and stored. 170

gallbladder GALL-blad-er A structure leading from the liver and toward the small intestine that stores bile. 757

gamete GAM-eet A sex cell. The sperm and ovum. 192

gametogenesis ga-MEET-o-gen-i-sis Meiosis and maturation; making gametes. 196

gametophyte gam-EET-o-fite Haploid stage of the plant life cycle. 192

gastric juice GAS-trik JUICE The fluid that stomach cells secrete that carries out chemical digestion. 760

gastrin GAS-trin A hormone that stomach cells secrete that stimulates secretion of more gastric juice. 760

gastrodermis gas-tro-DERM-is The inner tissue layer of a cnidarian. 517

gastrointestinal tract GAS-tro-in-TES-ti-nal TRAKT A continuous tubule along which food is physically and chemically digested. 757

gastropods GAS-tro-podz Snails and slugs. 519

gastrovascular cavity gas-tro-VASC-yu-lar CAV-it-ee The site of digestion in a cnidarian. 517

gastrula GAS-troo-la A three-layered embryo. 220

gemmae GEM-ay Structures that form asexually from liverworts that give rise to progeny. 494

gemmules GEM-yools Asexual structures in sponges. 516

gene A sequence of DNA that specifies the sequence of amino acids of a particular polypeptide. 51, 262

gene pool All the genes in a population. 404

generative nucleus GEN-er-ah-tiv NU-klee-us A haploid cell resulting from the mitotic division of a microspore in male plant reproduction. 563

genetic code Correspondence between specific DNA base triplets and amino acids. 51, 331

genetic drift Changes in gene frequencies caused by separation of a small group from a larger population. 408

genetic load Collection of deleterious alleles in a population. 410

genetic marker A detectable piece of DNA closely linked to a gene of interest whose precise location is unknown. 289

genotype JEAN-o-type Genetic constitution of an individual. 265

genotypic ratio jean-o-TIP-ik RAY-shee-o Proportions of genotypes among offspring of a genetic cross. 266

geological time scale A division of time into major eras of biological and geological activity, then periods within eras, and epochs within some periods. 359

germ cell Gamete or sex cell. 196

germinal mutation GER-min-al mew-TAY-shun A mutation in a sperm or oocyte. 341

germ layer A layer of the primordial embryo. 220

gibberellins GIB-ah-REL-inz A class of plant hormones that promote cell elongation and division in seeds, roots, shoots, and young leaves. 577

gill A highly folded respiratory surface for gas exchange in aquatic animals. 734

Ginkgo GEENG-ko A division of the gymnosperms; tree type. 499

gizzard The second part of a bird's stomach. 754

glomerular capsule glo-MER-u-lar KAP-sool The cup-shaped proximal end of the renal tubule that surrounds the glomerulus. 781

glomerular filtrate glo-MER-u-ler FIL-trate In a nephron in the kidney, the material that diffuses from the glomerulus to the glomerular capsule. 783

glomerulus glo-MER-u-lus A ball of capillaries between the afferent arterioles and efferent arterioles in the proximal part of a nephron. 780

glottis GLOT-is Opening from the pharynx to the larynx. 736

glucagon GLU-ka-gon A pancreatic hormone that breaks down glycogen into glucose, raising blood sugar levels. 664, 672

glucocorticoid GLU-ko-KOR-tah-koid Hormone that the adrenal cortex secretes that enables the body to survive prolonged stress. 667, 670

glycerol GLI-sir-all A three-carbon alcohol that forms the backbone of triglyceride fats. 45

glycocalyx gli-ko-CAY-lix A sticky layer of a bacterial cell wall that consists of proteins and/or polysaccharides. 446

glycolysis gli-KOL-eh-sis A catabolic pathway occurring in the cytoplasm of all cells. One molecule of glucose splits and rearranges into two molecules of pyruvic acid. 127

Gnetophyta NEE-to-fit-a A division of gymnosperms; tree type. 499

Golgi body GOL-gee bod-ee A system of flat, stacked, membrane-bounded sacs where sugars are polymerized to starches or bonded to proteins or lipids. 71

gonadotropic hormone go-NAD-o-TRO-pik HOR-moan A hormone made in the anterior pituitary that affects the ovaries or testes. 667

gradualism Slow evolutionary change. 415

granum GRAN-um A stack of flattened thylakoid discs that forms the inner membrane of a chloroplast. 74, 151

gravitropism grav-eh-TROP-izm A plant's growth response toward or away from gravity. 578

greenhouse effect Elevation in surface temperature caused by carbon dioxide buildup. 896

gross primary production Total amount of solar or geothermal energy converted to chemical energy in a certain time period by organisms in a given region. 863

ground tissue The tissue that makes up most of the primary body of a plant. 534

growth hormone (GH) A hormone produced in the pituitary gland that promotes growth and development of all tissues by increasing protein synthesis and cell division rates. 667

guanine GWAN-een One of the two purine nitrogenous bases in DNA and RNA. 51

guard cells Cells that control opening and closing of stomata in plants. 536

gymnosperm JIM-no-sperm Naked seed plant. 492

gynoecium guy-no-EE-see-um The second innermost whorl of a flower, consisting of female reproductive structures. 563

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