| A | B |
|---|
| genetic variation | not all organisms within a species are alike |
| embryo | organism before it's born |
| relatedness | how to organisms are similar |
| homologous structure | structures that are similar |
| natural selection | helping the species survive through choices |
| descent with modification | organism changed descendent of earlier org. |
| vestigial structure | part seems useless but useful to ancestor |
| radioactive mineral | gives off energy over time |
| extinct | no longer existing |
| evolution | process of change over time |
