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. During the process of evolution, only a small percentage of species has survived. Though all living things are related through a common ancestry, life continues to change resulting in the biodiversity we see today.