484 Glossary Apomixis (plural apomixes) A mode of clonal propagation by seeds, the embryos of which are totally genetic copies of the source plant Seeds are produced without fertilization, but often pollination is required to induce apomictic seed production Apomictic plants can also reproduce sexually, but this is very rare Apomorphic Describing derived characteristics, relative to a sister group Apomorphy A derived character or character state Aposematic Describing an organism that is rendered less susceptible to predation by somehow making known its obvious unpalatability, as by conspicuous odors, sounds, or coloration The fact of doing this is aposematism Apparent competition An indirect interaction between two prey species in which one experiences more intense predation, because the presence of the other brings about a change in predator abundance or behavior Aquaculture The commercial farming of aquatic organisms, including fish, mollusks, crustaceans, and aquatic plants Aquifer A geological formation that contains groundwater and allows its movement Arboreal Having to with or involving trees Living in or on trees Arboricolous Growing on or living in trees, or off the ground in large woody shrubs or on fallen tree trunks Archaea Microorganisms that are similar to bacteria in size and simplicity of structure but very different in molecular organization, often living in extreme environments They comprise (in addition to eukaryotes and bacteria) one of the three domains of life Archaic ungulate One of an extinct group or grade of mammals that possibly gave rise to hoofed mammals Also known as a CONDYLARTH Area cladogram A branching diagram that uses phylogenetic relationships to trace geographical changes (either dispersal events or barriers to dispersal) Area of endemism An area characterized by the congruent distributions of two or more groups of organisms Arid Describing a climate lacking in moisture, especially one having insufficient rainfall to support many trees or woody plants Such a condition is aridity Arrhenotokous Describing a reproductive mode in which unfertilized eggs develop into haploid males and fertilized eggs develop into diploid females This mode is Arrhenotoky Arthropod One of the Arthropoda, the phylum of jointlegged animals including insects, spiders, crustaceans, and others; the most species-rich phylum existing today Artificial ecosystem An ecosystem dominated by human artifacts and human-induced materials and energy flows Assemblage The collection of animals and plants found together in a patch of habitat Assisted colonization The translocation of species outside of their native range to allow them to track changes in climate Associational refuge A situation in which a potential prey escapes or deters a consumer by associating with another organism, thus interfering with the ability of the consumer to locate or attack the prey Assortative mating The tendency of like to mate with like, whether it is based on similarities in genotypes or similarities in phenotypes ATBI All taxa biodiversity inventory; the thesis, first suggested by D H Janzen, that it might be feasible to produce a complete species list for all the organisms living in one place; e.g., a hectare of tropical forest This goal has thus far proved elusive Atlantic Multidecadal Oscillation (AMO) A mode of variability occurring in the North Atlantic Ocean, principal expressed in the sea surface temperature (SST) Atmospheric deposition The process by which materials are deposited from the atmosphere to the Earth’s surface Atmospheric lifetime A time scale describing the rate of removal of a gas from the atmosphere, generally defined as the time for a 63.2% decrease (the e-folding time) in the global atmospheric burden of the gas; a period of many years for major greenhouse gases ATP synthetase A membrane-associated protein complex that couples exergonic fluxes of H þ across the membrane to ADP phosphorylation, or vice versa AUM Animal unit month Australasian One of the major zoogeographical regions of the world See ZOOGEOGRAPHICAL REGION Autapomorphy An advanced or derived character state unique to an individual taxon (of any rank) Autocatalysis The self-acceleration of certain chemical reactions that yield catalytically active products The reaction rate of autocatalytic processes increases exponentially Autochthonous Referring to the production of organic matter within an ecosystem, for example, primary production by aquatic plants Autogenic Describing a species that creates habitat for other organisms, in a habitat that would not exist for them if the autogenic species were not present Autotroph Literally, a self-feeder; an organism that is able to utilize inorganic carbon (carbon dioxide) as the sole carbon source for growth; for example, green plants and certain bacteria Such an organism is autotrophic Autotrophy The ability of organisms to grow and reproduce independent of external sources of organic carbon compounds Compare HETEROTROPHY Avirulent Not virulent; describing a parasite that has little impact on its host’s fitness AZA Association of Zoos and Aquariums, a North American professional organization Background extinction (rate) The natural rate of extinction over geological time, measured from the fossil record and independent of anthropogenic influence; characteristic of the major part of the evolution of life Background selection Selection that takes place at loci other than that of interest Such events can strongly increase the intensity of genetic drift as well as hinder the action of selection at a locus of interest These effects are normally modeled by reducing the effective population size applicable to the locus of interest Bacteria (singular bacterium) An entirely microbial domain of single-celled organisms, existing in various shapes and generally found throughout the Earth as well as in organic matter and the living bodies of humans and other organisms They are evolutionarily distinct from Archaea, and one of the three domains of life along with Archaea and Eukaryota Bacteriophage A virus that infects bacteria