| A | B |
|---|
| microevolution | a change over time in a population by the process of natural selection |
| theory | a well-tested explanation that unifies a broad range of observations |
| fossil | preserved remains or evidence of an ancient organism that usually occurs in sedimentary rock, crystallized sap, or is mummified, or frozen. |
| variation | the differences in a trait among individuals of a species in a population |
| artificial selection | selective breeding of organisms by humans to increase the frequency of desirable traits |
| struggle for existence | the competition among members of a species for food, living space, and the other necessities of life |
| fitness | the ability of an organism to survive in its environment and reproduce |
| adaptation | the inherited characteristic of a favorable trait that increases an organism's chance of survival |
| survival of the fittest | the process by which individuals that are better suited to their environment survive and reproduce most successfully; also called natural selection |
| natural selection | because variations exist in a population, individuals that are better suited to their environment survive and will reproduce most successfully, causing an increase in the favorable trait which will eventually become an adaptation |
| vestigial organ | a organ that serves no useful function in an organism |
| differential reproductive success | the reproduction of more offspring by individuals with a certain variation than by others without the variation in a population |
| macroevolution | process by with modern organisms have descended from ancient organisms |
