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Evolution: Natural Selection

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Presentation on theme: "Evolution: Natural Selection"— Presentation transcript:

1 Evolution: Natural Selection
Diane Philip

2 I. Definition of Evolution
Evolution is an inherited change in a group of organisms through time. This changes the phenotypic ratio of a population over time. Inherited: genetic transmission of information Group: no such thing as an individual evolving Time: evolution is a process occurring over generations

3 II. Differential Reproduction
Observation 1: Populations over-reproduce even though resources are limited. Conclusion 1: There will be competition over these resources and some organisms will survive to reproduce, while some will not.

4 II. Differential Reproduction
Observation 2: Individuals in a population vary and some of that variation is heritable. (ex. color of fur) Conclusion 2: Organisms that are well-suited to the environment will be more likely to reproduce than others, passing on these well-suited traits (if the trait is heritable). The next generation will most likely have a higher proportion of those traits. This is known as differential reproduction.

5 Differential Survival and Reproduction among the chickens

6 III. Evidence Homologous structures are shared traits the result from common ancestry. This means they evolved from the same structure and have a similar function.

7 III. Evidence Analogous structures are shared traits that result from similar environmental demands, not from common ancestry (convergent evolution). This means that they have a similar function but evolved separately.


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