Fossils provide the evidence for the history of life on Earth. A fossil is any trace of an animal or plant that was once alive. Fossil evidence indicates that life has changed over time. Fossils help us to identify the relationships among groups of related organisms. Closely related organisms share features inherited from common ancestors.
Scientists use diagrams called cladograms to illustrate evolutionary relationships.
Morphological features, and DNA can provide scientists with information about ancestry. Even though related organisms inherit common features, variations exist within populations. Variation contributes to the process of evolution. Natural selection and variation together cause evolutionary change. Natural selection is not the only mechanism of evolution.