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Evolution

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Natural Selection I.

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BI. 8. a. Students know how natural selection determines the differential survival of groups of organisms. BI.7 a. Students know why natural selection acts on the phenotype rather than the genotype of an organism. BI7. d. Students know variation within a species increases the likelihood that at least some members of a species will survive under changed environmental conditions.

Standards:

SWBAT…  Explain how natural selection determines the differential survival of groups of organisms.  Explain how variation within a species increases the likelihood that at least some members of a species will survive under changed environmental conditions.

Objectives:

Natural variations appear in populations because of genetic variations.  These natural variations can lead to beneficial adaptations.  Beneficial adaptations will appear in future generations because of the principles of natural selection.  These “ natural selections” drive evolution by changing the inherited characteristics of the population. 

Review-What we know so far….

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Natural selection-mechanism by which individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals.

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These adaptations occur over many generations in a population (descent with modification)

What is natural selection’s role in evolution?

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NS explains how evolution can occur

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Natural selection acts on phenotypes (physical traits), not on genetic material.

What is natural selection’s role in evolution?

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Overproduction-jaguar produces more offspring than can survive Variation-some jaguars are born with larger teeth and jaws Adaptation-jaguars with larger teeth and jaws are able to eat shelled reptiles, and leave more offspring Descent with modification-large teeth and jaws are inherited and become more common

The Four Principles of Natural Selection

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What causes the natural variations that occur in a population? Does natural selection act on the genotype or phenotype of organisms? Where do species get their adaptations from? How does natural selection cause evolution?

Summary Questions: