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Published byMariah Cain Modified over 9 years ago
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Natural Variation Even within a species individuals vary from each other
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Discussion Question These are the same species of moth. The two are naturally occurring variations. Describe situations where the coloration would be an advantage for the moth.
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How We Use Variation Artificial selection – nature provides the variation and humans select the variations they find useful
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Evolution by Natural Selection Natural Selection – the traits being selected (which therefore increase over time) contribute to an organism’s fitness in its environment
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Natural Selection The struggle for existence Survival of the fittest Descent with modification
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Struggle for Existence Members of each species compete regularly to obtain food, living space, and other necessities of life Run fast, behavioral tactics, camouflage
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Survival of the Fittest Individuals better designed for the environment where they live will survive and reproduce most successfully Fitness is the result of successful adaptations
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Survival of the Fittest Fitness – the ability to survive and reproduce in a specific environment Adaptation – an inherited characteristic that increases an organism’s chance of survival
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Discussion Question Give three examples of animals with designs that help their survival.
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Tale of the Peacock Online Video Clip http://www.pbs.org/wgbh/evolution/educ ators/course/session4/explain_a.html http://www.pbs.org/wgbh/evolution/educ ators/course/session4/explain_a.html Or: “Why Sex?” (PBS Evolution Series) minutes 17:00 – 28:00
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KEY CONCEPT Over time, natural selection results in changes in the inherited characteristics of a population. These changes increase a species’ fitness in its environment.
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Common Descent
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Evidence for Evolution 1) Fossil record 2) Animals with similar selection pressures evolve similar features 3) Homologous structures 4) Similarities in early development
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Genetic Toolkit Online Video Clip http://www.pbs.org/wgbh/evolution/educ ators/course/session4/engage_a.html http://www.pbs.org/wgbh/evolution/educ ators/course/session4/engage_a.html (5 min)
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similar habitats & similar structures
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homologous structures
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similarities in embryology
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