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.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).These all develop through an embryo that is enclosed within a membrane called an amnion.
Within a population there may be many different alleles of a gene; each has a unique nucleotide sequence.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.Also used to describe the process of genetic change within a population, as influenced by natural selection.adaptive landscape: A graph of the average fitness of a population in relation to the frequencies of genotypes in it.They have moist scaleless skin which is used to supplement the lungs in gas exchange.