| A | B |
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| adaptation | a characteristic that improves an individual's ability to survive and reproduce in a particular environment |
| species | a group of organisms that are closely related and can mate to produce fertile offspring |
| evolution | the process in which inherited characteristics within a population change over generations such that new species sometimes arise |
| fossil | the trace or remains of an organism that lived long ago, most commonly preserved in sedimentary rock |
| fossil record | a historical sequence of life indicated by fossils found in layers of the Earth's crust |
| trait | a genetically determined characteristic |
| selective breeding | the human practice of breeding animals or plants that have certain desired traits |
| natural selection | the process by which individuals that are better adapted to their environment survive and reproduce more successfully than less well adapted individuals do; a theory to explain the mechanism of evolution |
| generation time | the period between the birth of one generation and the birth of the next generation |
| speciation | the formation of new species as a result of evolution |
