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Natural selection
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This means No Change or No Evolution.

Slide 22

Macroevolution

Macroevolution

The origin of taxonomic groups higher than the species level.

Slide 23

Microevolution

Microevolution

A change in a populations gene pool over a secession of generations.

Evolutionary changes in species over relatively brief periods of geological time.

Slide 24

Five Mechanisms of Microevolution

Five Mechanisms of Microevolution

1. Genetic drift:

Change in the gene pool of a small population due to chance.

Two examples:

a. Bottleneck effect

b. Founder effect

Slide 25

a. Bottleneck Effect

a. Bottleneck Effect

Genetic drift (reduction of alleles in a population) resulting from a disaster that drastically reduces population size.

Examples:

1. Earthquakes

2. Volcanos

Slide 26

b. Founder Effect

b. Founder Effect

Genetic drift resulting from the colonization of a new location by a small number of individuals.

Results in random change of the gene pool.

Example:

1. Islands (first Darwin finch)

Slide 27

Five Mechanisms of Microevolution

Five Mechanisms of Microevolution

2. Gene Flow:

The gain or loss of alleles from a population by the movement of individuals or gametes.

Immigration or emigration.

Slide 28

Five Mechanisms of Microevolution

Five Mechanisms of Microevolution

3. Mutation:

Change in an organisms DNA that creates a new allele.

4. Non-random mating:

The selection of mates other than by chance.

5. Natural selection:

Differential reproduction.

Slide 29

Modes of Action

Modes of Action

Natural selection has three modes of action:

1. Stabilizing selection

2. Directional selection

3. Diversifying selection

Slide 30

1. Stabilizing Selection

1. Stabilizing Selection

Acts upon extremes and favors the intermediate.

Slide 31

2. Directional Selection

2. Directional Selection

Favors variants of one extreme.

Slide 32

3. Diversifying Selection

3. Diversifying Selection

Favors variants of opposite extremes.

Slide 33

Speciation

Speciation

The evolution of new species.

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