species
a group of similar organisms that can mate with each other and produce fertile offspring
fossil
the preserved remains or traces of an organism that lived in the past
adaptation
a trait that helps an organism survive and reproduce
evolution
the gradual change in a species over time
scientific theory
a well-tested concept that explains a wide range of observations
natural selection
the process by which individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species
variation
any difference between individuals of the same species
homologous structures
parts that are similar in related species; provide evidence of inheritance from common ancestor
branching tree
a diagram that shows how scientists think different groups of organisms are related
vestigial structures
parts of an organism that have no apparent use, inherited from an ancestor with a usable form of the part
embryology
the branch of biology that deals with early development of organisms
selective breeding
the process by which humans breed plants and animals to develop particular characteristics
trait
a characteristic that an organism can pass on to its offspring
inheritance
the passing of traits from parents to biological offspring
ancestor
a deceased organism from which other organisms are descended, usually by many generations
DNA
the genetic material, found in an organism's cells, that carries information about an organism and is passed from parent to offspring
extinct
a species that does not have any living members