Put these events in order. A new selective pressure occurs. A pop. contains genetic variation as a result of mutation. Allele (gene) frequencies within the pop. change Reproduction occurs. Environmental change occurs.

Microevolution The study of how populations change genetically over time.

Individuals don’t evolve; populations do Population – a group of individuals of the same species that are occupying a given area.

Definition of Evolution A change in a population’s frequencies of alleles or genotypes (microevolution) Can you name any microevolutionary processes? In other words, what drives evolution?

What causes allele frequencies to change? 1. Mutations (insertions, deletions, etc.) and crossing over (event in meiosis) 2. Gene flow (Migration) 3. Genetic drift (disasters and random chance) 4. Natural selection

There are 4 forces of change or causes of Microevolution 1.Mutations (insertions, deletions, etc.) and crossing over (event in meiosis) Animation Quiz 4 - Addition and Deletion Mutations 2. Gene flow – The physical movement of alleles into and out of a pop., through migration.

Gene Flow

3. Genetic drift – Random change in allele frequencies brought about by chance alone.

Genetic Drift

Cheetahs, which have very little genetic variation, are presumed to have gone through several genetic bottlenecks.

Genetic Drift The Torrey pine has also reached a genetic bottleneck in the small grove of trees that survives to this day at Torrey Pines State Park. Protein analysis of the pines shows practically no variability between individual trees. This lack of variability could seriously threaten their survival if the climate changes significantly. The population may not contain the genetic variability (gene pool) to adapt to a significant environmental change.

Example of Genetic Drift Flash Tutorial Factors causing allele frequencies to change

Natural Selection Organisms with certain traits are more likely to survive and reproduce than are organisms with other characteristics.