the gradual change in a species over time
Differences between members of the same species.
A characteristic that helps an organism survive or reproduce in its environment.
A natural process resulting in the evolution of organisms best adapted to the environment
the disappearance of a species when the last of its members dies.
the remains (or an impression) of a plant or animal that existed in a past geological age and that has been excavated from the soil
chronological collection of life's remains in sedimentary rock layers