| Evolution | Gradual change over time due to mutations. |
| Charles Darwin | Scientist who came up with the theory of natural selection. |
| Natural selection | Idea that organisms with the best traits will live to reproduce and pass on their genetic information. |
| Homologous Structures | Structures from two different organisms that look similar because organisms came from a common ancestor. |
| Vestigial Structure | A structure that is no longer in use but was useful at one time; ex. snakes have remnants of a pelvis and femur |
| Adaptation | A trait that helps an organism survive in the wild. |
| Galapagos Island | Island off the coast of South America where Darwin studied organisms. |
| Gene pool | Sum of all genes in a population. |
| Geographic isolation | Occurs when a species is separated by distance and may evolve into two different species over time; break up of pangea led to geographic isolation of many animals |
| Mutation | A change in one of the nitrogen bases in DNA. |