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adaptation: A change in an organism that improves its ability, and the ability of its offspring, to survive in an environment.
Cambrian Explosion: a roughly ten-million-year period that began about 542 million years ago, during which all of the most complex life forms appeared.
common ancestor: An ancestor shared by two or more descendant species.
natural selection: An evolutionary mechanism whereby individuals tend to pass on heritable features that enable them to cope better with their environment to future generations. Over time, populations of individuals will exhibit more of the better-adapted features.
primate: A member of the order Primates, which includes lemurs, monkeys, apes, and hominids.
variation: Genetic variation represents differences between individual members of a species. Variation comes from both recombination of parental DNA and genetic mutation

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