1. Natural Selection

2. What do you think term speciation is referring to?
Monday, March 2nd
What do you think term speciation is referring to?

3. Natural Selection
Process that results in adaptation of a population to the biotic and abiotic environments
Biotic: includes organisms that seek resources through competition, predation, and parasitism
Abiotic: Includes weather conditions dependent upon temperatures and precipitation

4. Evolution by natural selection requires:
Variation: Members of population differ from one another
Inheritance: Many of these differences are heritable genetic differences
Differential Adaptedness: Some of these differences affect how well an organism is adapted to its environment
Differential Reproduction: Individuals better adapted to the environment are more likely to reproduce

5. Types of Selection Directional selection Disruptive selection
Favors individuals at one end of the phenotypic range
Disruptive selection
Favors individuals at both extremes of the phenotypic range
Stabilizing selection
Favors intermediate variants and acts against extreme phenotypes

6. (a) Directional selection shifts the overall makeup of the population by favoring variants at one extreme of the distribution. In this case, darker mice are favored because they live among dark rocks and a darker fur color conceals them from predators.
(b) Disruptive selection favors variants at both ends of the distribution. These mice have colonized a patchy habitat made up of light and dark rocks, with the result that mice of an intermediate color are at a disadvantage.
(c) Stabilizing selection removes extreme variants from the population and preserves intermediate types. If the environment consists of rocks of an intermediate color, both light and dark mice will be selected against.
Phenotypes (fur color)
Original population
Original
population
Evolved
Frequency of individuals

7. The Preservation of Genetic Variation
Various mechanisms help to preserve genetic variation in a population
Diploidy: Maintains genetic variation in the form of hidden recessive alleles
Creates a heterozygous advantage