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Evolution and Genetic Variation

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Submitted By bconcepcion
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Review - For natural selection to occur individuals in a population must vary from one another. The variations may be visible (Eye color) or on the molecular level (Blood type). Only those traits that can be inherited are relevant to natural selection.
Where does genetic variation come from? 1. Genetic variation is random and caused by mutation. Random changes in a gene can result in a new allele. This new allele may be helpful or detrimental. 2. Sexual reproduction results in a unique combination of alleles that each individual inherits. Unique genetic combinations are the result of independent assortment in meiosis, random fertilization and crossing over
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Genetic variation is caused by random processes but natural selection is not random!!!

Mechanisms of Evolution
Evolution is a change in a population’s genetic makeup from generation to generation. What causes a gene pool to change over time? 1. Natural Selection (we already discussed)
Individuals that function best in an environment have the most offspring. More of their genes are represented in subsequent generations. These individuals are said to be “fit”. Not necessarily the biggest, fastest, or strongest. Good enough to survive and reproduce. Relative fitness compares the fitness of different individuals.

Examples of natural selection: Panda’s Thumb, Foxes

Sexual selection is a form of natural selection in which individuals with certain traits are more likely than other individuals to obtain mates. Secondary sex characteristics may be used to compete with members of the same sex. Examples: Physical combat or ritualized displays. One sex may be choosy in selecting their mates. Peacock tail sexually selected. Sexual selection often accounts for male/female differences in many animal species. There is some evidence that sexual selection accounts for differences in human male/female...

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