Mechanisms of Evolution. Chapter 16 and Chapter 17. How Does Evolution Work?. Individual organisms cannot evolve. Populations of a particular species evolve. Natural selection acts on the range of phenotypes in a population.
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Chapter 16 and Chapter 17
1. Geneflow: Transport of genes by migrating individuals.
2. Nonrandom Mating: Mating based on preferences
Example: a female may choose a mate based on male size, color, or ability to gather food.
3. Mutation: Change in DNA
4. Genetic Drift: chance event changes allelic frequencies – Greatly affect small populations such as the animals of the Galapagos Islands or Amish.
Diane Dodd’s fruit fly lab, 1989
A physical barrier that separates a population into groups.
Similar species have different breeding seasons
Eastern Spotted Western Spotted
Similar species may have different courtship or mating behaviors.
Ex: Eastern & Western meadowlarks almost identical in color shape and habitat, but difference in courtship rituals differ different species
Ex: Stickleback fish one is a bottom feeder, one spends time in the top open layers of lakes in British Columbia, Canada
2. Convergent Evolution– Unrelated species occupy similar environments in different parts of the world.
Similar pressures of natural selection lead to similar adaptations.
Example of Convergent America, and the elephant, still found in Asia and Africa are presumed to have evolved from a common ancestor.
A Hummingbird Moth
A Humming Bird
Rhea America, and the elephant, still found in Asia and Africa are presumed to have evolved from a common ancestor.
The End America, and the elephant, still found in Asia and Africa are presumed to have evolved from a common ancestor.