The diameter of the aperture determines the intensity of light admitted. archeology: The study of human history and prehistory through the excavation of sites and the analysis of physical remains, such as graves, tools, pottery, and other artifacts.
The pupil of a human eye is a self-adjusting aperture. archetype: The original form or body plan from which a group of organisms develops.
allopatric speciation: Speciation that occurs when two or more populations of a species are geographically isolated from one another sufficiently that they do not interbreed. There are 20 main amino acids in the proteins of living things, and the properties of a protein are determined by its particular amino acid sequence.analogous structures: Structures in different species that look alike or perform similar functions (e.g., the wings of butterflies and the wings of birds) that have evolved convergently but do not develop from similar groups of embryological tissues, and that have not evolved from similar structures known to be shared by common ancestors. Note: The recent discovery of deep genetic homologies has brought new interest, new information, and discussion to the classical concepts of analogous and homologous structures.anatomy: (1) The structure of an organism or one of its parts. ancestral homology: Homology that evolved before the common ancestor of a set of species, and which is present in other species outside that set of species. anthropoid: A member of the group of primates made up of monkeys, apes, and humans.The term can also be applied to larger groups of organisms, as in "the adaptive radiation of mammals." adaptive strategies: A mode of coping with competition or environmental conditions on an evolutionary time scale.Species adapt when succeeding generations emphasize beneficial characteristics.