Geological dating radioactive isotope
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.
artifact: An object made by humans that has been preserved and can be studied to learn about a particular time period.
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.
ammonoid: Extinct relatives of cephalopods (squid, octopi, and chambered nautiluses), these mollusks had coiled shells and are found in the fossil record of the Cretaceous period.
amniotes: The group of reptiles, birds, and mammals.
Then, even if circumstances change such that it no longer provides any survival or reproductive advantage, the behavior will still tend to be exhibited -- unless it becomes positively disadvantageous in the new environment.
adaptive radiation: The diversification, over evolutionary time, of a species or group of species into several different species or subspecies that are typically adapted to different ecological niches (for example, Darwin's finches).allometry: The relation between the size of an organism and the size of any of its parts.For example, an allometric relation exists between brain size and body size, such that (in this case) animals with bigger bodies tend to have bigger brains.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.In a diploid cell there are usually two alleles of any one gene (one from each parent).