Chapter+15

**__Chapter 15__** **__Section 1__**  fossil: the remains or traces of a once-living organism

biogeography: the study of the geographical distribution of fossials and living organisms

sediment: dust, sand, or mud deposited over time by wind or water.

mold: a type of fossil formed from an impression of the shape or tracks of an organism

cast: a type of fossil formed when sediments fill in the cavity left by a decomposing organism

law of superpostition: a law that states that successive layers of rock or soil were deposited on top of one another & the lowest level is oldest

stratum: in geology, a layer of soil or rock in a cross-section of the earth

relative age: if a given fossil was younger or older than another fossil

absolute age: its age in years

extinct: the dying out of species

mass extinction: one of the brie periods of time during which large numbers of species disappeared

acquired trait: one that is not determined by genes
 * __Section 2__**

natural selection: the process by which organisms with favorable variations reproduce at higher rates than those without such variables.

population: all the members of a species that live in the same area and make up a breeding group

uniformitarianism: a principle that states that the geological structure of earth resulted from cycles of observable processes and that these processes operate continuously

adapt: in populations, to change genetically over generations to become more suited to the environment

fitness: a measurment of the ability of a species to respond to the pressures of natural selection: the ability of individuals to survive to propagate their genes

adaptive advantage: a favorable trait

homologous: similar features that originated in a shared ancestor
 * __Section 3:__**

analogous: in evolution, structures in more than one organism that have similar appearance & function but different embryological origin

vestigial: referring to a functionless structure that was functional in an ancestrol species

conserved: remained unchanged

coevolution: the mutual evolution of two different species interacting with each other

convergent evolution: the process by which unrelated species become more similar as they adapt to the same kind of enviorment

divergent evolution: the process of two or more related species becoming more and more dissimilar

adaptive radiation:an evolutionary pattern in which many species evolve from a single ancestral species

artificial selection: breeding of organisms by humans for specific phenotypic characteristics