Lewis/Life - Glossary

B

bacilli ba-SILL-i Rod-shaped bacteria. 443

Bacteria bac-TEAR-e-a One of the three domains of life, prokaryotes. 430

balanced polymorphism BAL-anced POL-ee-MORF-iz-um Stabilizing selection that maintains a genetic disease in a population because heterozygotes resist an infectious disease. 411

bark Tissues outside the vascular cambium. 551

Barr body BAR BOD-ee The dark-staining body in the nucleus of a female mammal's cell, corresponding to the inactivated X chromosome. 294

base A molecule that releases hydroxide ions into water. 40

basement membrane A thin layer in human skin that separates the epidermis from the dermis. 599

basidia bass-ID-ee-a Spore-bearing structures in basidiomycetes. 482

basidiomycete bass-ID-eo-mi-SEET Fungus that has club-shaped hyphae tips that contain spore-bearing basidia. 478

basilar membrane BA-sill-ar MEM-brane The membrane beneath hair cells in the cochlea of the inner ear that vibrates in response to sound. 653

B cells Lymphocytes that produce antibodies. 716, 791

benign tumor bee-NINE TOO-mer A noncancerous tumor. 180

benthic zone BEN-thick ZONE The bottom of the ocean. 883

bilaterally symmetrical bi-LAT-er-a-lee sim-MET-rik-al An animal body form in which only one plane divides the animal into mirror image halves. 512

bile A digestive biochemical that emulsifies fats. 757

binary fission BI-nair-ee FISH-en A type of asexual reproduction in which a cell divides into two identical cells. 192, 448

bioaccumulation bi-o-a-cume-u-LAY-shun Higher concentration of a chemical in cells than in the nonliving surroundings. 866

biodiversity bi-o-di-VER-city The spectrum of different life-forms. 12

bioenergetics bi-o-n-er-JET-ix The study of energy in life. 110

biogeochemical cycles bi-o-gee-o-kem-i-kal SI-kulls Geological and biological processes that recycle chemicals vital to life. 864

biogeography bi-o-gee-OG-grah-fee The physical distribution of organisms. 374

biological evolution The process by which the genetic structure of populations changes over time. 374

bioluminescence bi-o-loom-in-ES-ents A chemical reaction that causes an organism to glow. 118

biomagnification bi-o-mag-nif-i-KAY-shun Increasing concentrations of a chemical with higher trophic levels. 866

biomes BI-ohms Major types of communities and ecosystems that are recognizable in large geographic areas. 859, 872

bioremediation bi-o-ree-meed-e-AY-shun Using organisms that metabolize toxins to clean the environment. 454, 890

biosphere BI-o-sfere The ecosystem of the entire planet. 9, 858

biotic community bi-OT-ik cum-MUNE-it-ee All the organisms in an area. 854

biotic succession bi-ot-ik suk-SESH-in Change among the populations in a biotic community. 856

bipedalism by-PEED-a-liz-m Walking upright on two limbs. 368

biramous bi-RAYM-us A double-branched arthropod appendage. 522

bivalve BI-valv A mollusk that has a two-part shell. 519

blade The flattened region of a leaf. 541

blastocyst BLAS-toe-syst Stage of human prenatal development that is a hollow, fluid-filled ball of cells. 218

blastomere BLAS-toe-mere A cell in a preembryonic organism resulting from cleavage divisions. 218

blastopore BLAS-toe-pour An indentation in a protostome embryo that develops into a mouth. 513

blood A complex mixture of cells suspended in a liquid matrix that delivers nutrients to cells and removes wastes. 594

blood-brain barrier Close knit cells of blood vessels in the brain, which limit substances that can enter the brain. 635

blood pressure The force blood exerts against blood vessel walls. 725

bolus BO-lus Food rolled into a lump by the tongue. 760

bond energy The energy required to form a particular chemical bond. 115

bone A connective tissue consisting of bone-building osteoblasts, stationary osteocytes, and bone-destroying osteoclasts, embedded in a mineralized matrix infused with spaces and canals. 594

boom and bust cycle A population that repeatedly and regularly increases and decreases in size. 844

braced framework A skeleton built of solid structural components strong enough to resist collapsing. 683

bracts BRAKS Floral leaves that protect developing flowers. 544

brain stem Part of the human brain closest to the spinal cord; controls vital functions. 625

bronchi BRON-ki Two tubules that branch from the trachea as it reaches the lungs. 737

bronchiole BRON-ki-ol Microscopic branch of the bronchi within the lungs. 737

bryophyte BRI-o-fite Plant that lacks vessels, including the mosses, liverworts, and hornworts. 492

budding Formation of a small progeny cell from a protozoan cell. 459

buffer system Pairs of weak acids and bases that maintain body fluid pH. 41

bulbourethral glands BUL-bo-u-REE-thral GLANZ Small glands near the male urethra that secrete mucus. 197

bulk element An element that an animal requires in large amounts. 32

bundle-sheath cell BUN-dull SHEETH SEL Thick-walled plant cell surrounding veins that functions in C4 photosynthesis. 160

bursae BURR-say Small packets in joints that secrete lubricating fluid. 700

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