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.
Amphibian larvae are aquatic, and have gills for respiration; they undergo metamorphosis to the adult form.
Most amphibians are found in damp environments and they occur on all continents except Antarctica.
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.
amphibians: The class of vertebrates that contains the frogs, toads, newts, and salamanders.
amniotes: The group of reptiles, birds, and mammals.
agnostic: A person who believes that the existence of a god or creator and the nature of the universe is unknowable.
algae: An umbrella term for various simple organisms that contain chlorophyll (and can therefore carry out photosynthesis) and live in aquatic habitats and in moist situations on land. Algae range from macroscopic seaweeds such as giant kelp, which frequently exceeds 30 m in length, to microscopic filamentous and single-celled forms such as Spirogyra and Chlorella. For example, if a gene determines the seed color of peas, one allele of that gene may produce green seeds and another allele produce yellow seeds.
These all develop through an embryo that is enclosed within a membrane called an amnion.
The amnion surrounds the embryo with a watery substance, and is probably an adaptation for breeding on land.