Explain how Natural Selection works. How many species in the world have humans identified? Is 99.9% of life extinct?

Name: Exam 1 Study Guide
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Bio Study guide Exam 1 Natural Selection: - 30-50 million species and we've only identiﬁed 2 million - 99.9% of life is extinct - Earth is 4.6 bill years old, life has been here for 3.8 bill Evolution- descent with modiﬁcation Order —> family —> genus —> species Evolution occurs through: - natural selection - genetic drift - gene ﬂow - mutation Natural Selection: unequal reproductive success (non random) - survival of the ﬁttest 1) individuals vary 2) variation is heritable 3) organisms produce more organisms than will survive 4) better adapted individuals will have more offspring Adaption - a trait that increases an individuals “ﬁtness” - comes from random changes (mutations) -