| A | B |
|---|
| species | a group of organisms that share similar characteristics and can reproduce among thensilves to produce fertile offspring |
| evolution | change in inherited characteristics over time |
| natural selection | organisms with traits best suited to their environment are more likely to survive and reproduce |
| variation | an ingerited trait that makes an individual different from other members of the same species |
| adaptation | any variation that makes an organism better suited for its environment |
| gradualism | model that describes evolution as a slow, ongoing process by which one species changes to a new species |
| punctuated equilibrium | the model of evolution in which rapid evolution comes about when the mutation of a few genes results in a new species suddenly changing into a new species |
| sedimentary rock | formed when layers of sand, silt, clay, or mud are compacted and cemented together, or when minerals are deposited from a solution |
| radioactive element | gives off steady amounts of radiation as it slowly changes to a nonradioactive element |
| embryology | the study of embryos and their development |
| homologous | body parts that are similar in structure and function |
| vestigial structures | structures that don't seem to have a function |
| primates | group of mammals including humans, monkeys, and apes that share characteristics such as opposable thumbs, binocular vision, and flexible shoulders |
| hominids | humanlike primate that appeared about 4 million to 6 million years ago, ate both plants and meat, and walked upright on two legs |
| Homo sapiens | early humans that likely evolved from Cro-Magnons |
