big bang theory- the theory that states that the universe formed by rapid expansion of matter and energy from an initial infinitely small, dense point
biological species- a group of interbreeding organisms that can produce fertile offspring
eukaryotic cell - a type of cell that has a membrane-bound nucleus and membrane-bound organelles
evolution- the process by which inherited characteristics within a population change over generations
fossil- remains or traces of organisms preserved over long periods of time
geologic time scale- an organizational chart that chronologically divides the natural history of earth into eras and
periods
homologous structures- structures that occur in different species but are similar enough to suggest that the species had a common ancestor
natural selection- the process by which species pass on the beneficial traits that help them survive
prokaryotic cell- a type of cell without a membrane-bound nucleus and without membrane-bound organelles, considered by scientists to be a more primitive type of cell than the more complex eukaryotic cells
selective breeding- the process of breeding organisms with the most desirable traits
speciation- when natural selection leads to an entirely new species
theory- an explanation or model of related natural events that can be tested by observations or experiments
vestigial structures- Â structures that appear to have no function for the organism but probably had a function in an ancestral organism
