bacteria: Tiny, single-celled, prokaryotic organisms that can survive in a wide variety of environments. Some cause serious infectious diseases in humans, other animals, and plants.
base: The DNA molecule is a chain of nucleotide units; each unit consists of a backbone made of a sugar and a phosphate group, with a nitrogenous base attached. The base in a unit is one of adenine (A), guanine (G), cytosine (C),or thymine (T). In RNA, uracil (U) is used instead of thymine. A and G belong to the chemical class called purines; C, T, and U are pyrimidines.
Batesian mimicry: A kind of mimicry in which one non-poisonous species (the Batesian mimic) mimics another poisonous species.
belemnite: An extinct marine invertebrate that was related to squid, octopi, and chambered nautiluses. We know from the fossil record that belemnites were common in the Jurassic period and had bullet-shaped internal skeletons.
big bang theory: The theory that states that the universe began in a state of compression to infinite density, and that in one instant all matter and energy began expanding and have continued expanding ever since.
biodiversity (or biological diversity): A measure of the variety of life, biodiversity is often described on three levels. Ecosystem diversity describes the variety of habitats present; species diversity is a measure of the number of species and the number of individuals of each species present; genetic diversity refers to the total amount of genetic variability present.
bioengineered food: Food that has been produced through genetic modification using techniques of genetic engineering.
biogenetic law: Name given by Haeckel to recapitulation.
biogeography: The study of patterns of geographical distribution of plants and animals across Earth, and the changes in those distributions over time.
biological species concept: The concept of species, according to which a species is a set of organisms that can interbreed among each other. Compare with cladistic species concept, ecological species concept, phenetic species concept, and recognition species concept.
biometrics: The quantitative study of characters of organisms.
biosphere: The part of Earth and its atmosphere capable of sustaining life.
bipedalism: Of hominids, walking upright on two hind legs; more generally, using two legs for locomotion.
bivalve: A mollusk that has a two-part hinged shell. Bivalves include clams, oysters, scallops, mussels, and other shellfish.
Blackmore, Susan: A psychologist interested in memes and the theory of memetics, evolutionary theory, consciousness, the effects of meditation, and why people believe in the paranormal. A recent book, The Meme Machine, offers an introduction to the subject of memes.
blending inheritance: The historically influential but factually erroneous theory that organisms contain a blend of their parents' hereditary factors and pass that blend on to their offspring. Compare with Mendelian inheritance.
botanist: A scientist who studies plants.
brachiopod: Commonly known as "lamp shells," these marine invertebrates resemble bivalve mollusks because of their hinged shells. Brachiopods were at their greatest abundance during the Paleozoic and Mesozoic eras.
Brodie, Edmund D., III: A biologist who studies the causes and evolutionary implications of interactions among traits in predators and their prey. Much of his work concentrates on the coevolutionary arms race between newts that posess tetrodotoxin, one of the most potent known toxins, and the resistant garter snakes who prey on them.
Brodie, Edmund D., Jr.: A biologist recognized internationally for his work on the evolution of mechanisms in amphibians that allow them to avoid predators. These mechanisms include toxins carried in skin secretions, coloration, and behavior.
Bruner, Jerome: A psychologist and professor at Harvard and Oxford Universities, and a prolific author whose book, The Process of Education, encouraged curriculum innovation based on theories of cognitive development.
bryozoan: A tiny marine invertebrate that forms a crust-like colony; colonies ofbryozoans may look like scaly sheets on seaweed.
Burney, David: A biologist whose research has focused on endangered species, paleoenvironmental studies, and causes of extinction in North America, Africa, Madagascar, Hawaii, and the West Indies.