Evidence for Evolution Charles Darwin, Age 31

Evolution: The gradual change in a species over time.

Evidences for Evolution: How do scientists know about organisms that lived long ago? What are some evidences that evolution has occurred?

1)The Fossil Record Fossils -- preserved remains or traces of an organism that lived in the past Gives clues about how/when new groups of organisms evolved.

Evolution of the Horse

How fast does evolution occur? There are two theories:

Punctuated Equilibria Gradualism Species undergo slow and steady change over time Punctuated Equilibria Short periods of rapid change separated by long periods of no change

2) Similarities in Body Structure Bones of different organisms have a similar arrangement.

Homologous Structures: Similar structures that related species have inherited from a common ancestor.

3) Similarities in Early Development During early development many different animals look similar >> indicates that animals share a common ancestor.

4)Similarities in DNA All living things use DNA to carry genetic info The more closely related two species are, the more genes they have in common.

Ex. Apes and human share more genes than humans and horses Ex. Apes and human share more genes than humans and horses. In fact, chimps and humans share 99.4% of their DNA!

5) Combining the Evidence Branching Tree -- A diagram that shows how scientists think different groups of organisms are related.