Evolutionary theory

Evolutionary theory is how scientists think species change over time. Scientists believe that all species come from a common ancestor and have changed over years. Through a process called natural selection, some animals survive while others don't. The animals that survive become the ones that reproduce and pass their genes on to the next generation. Over time, the traits that help an animal survive better will be passed to more and more animals--so that eventually the species looks and behaves differently than it did before. This is how scientists think species change over time.