Evolutionary Evidence Chapter 1.3

Theory A widely accepted statement based on scientific evidence that help explain a group of facts. Theories can change if new evidence is found.

Three different types of evidence provide a bigger picture of evolution fossil genetic biological

Ancestor An early form of an organism from which later form descended.

Fossil Show that organisms that lived in the past are similar to species living today. Two species with a common ancestor can develop differently in different locations.

Biological: Similarities in Structure Vestigial Structures Organs that were fully functional in an ancestral group, but are unused in later species. Whales and snakes have small leg bones Similar structures with different functions. Indicates common ancestor. Page 31

Biological: Similarities In development The study of embryos shows that animals that appear to be very different as adults are similar during early development. Page 32

Genetic Scientists can tell how closely organisms are related by comparing DNA. Compare human gene to a mouse gene.