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a group of organisms that are physically similar and can mate with each other and produce offspring that can also mate and reproduce
a behavior or physical characteristic that allows an organism to survive or reproduce in its environment
a process by which individuals that are better adapted to their environment are more likely to survive and reproduce than others of the same species
body parts that are structurally similar in related species and that provide evidence for a common ancestor
a type of fossil formed when a shell or other hard part of an organism dissolves, leaving an empty space in the shape of the part
a technique used to determine the actual age of a fossil on the basis of the amount of a radioactive element it contains
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