Evolution of Populations

1. Evolution of Populations

2. Mutation Gene Flow Non-random mating Genetic Drift Selection Title: Types of Evolutionary Change

3. 1. Mutation & Variation • Mutation creates variation • Mutation changes DNA sequence, changes amino acid sequence, and changes proteins.

4. 2. Gene Flow • Movement of individuals and their alleles in & out of populations • Causes genetic mixingacross regions • seed & pollen distribution by wind & insect • migration of animals • sub-populations may have different allele frequencies • reduce differences between populations

5. 3. Non-random mating • Sexual selection • Organisms may prefer to mate with others of the same genotype or of different genotypes.

6. Warbler finch Tree finches Ground finches 4. Genetic drift • 2 types: • founder effect • small group splinters off & starts a new colony • bottleneck • some factor (disaster) reduces population to small number & then population recovers & expands again

7. 4. Genetic drift • Founder Effect- When a new population is started by only a few individuals. • some rare alleles may be at high frequency; others may be missing • skew the gene pool of new population • human populations that started from small group of colonists • example: colonization of New World

8. Bajau People • https://www.youtube.com/watch?v=T3fOf5YZI-Q

9. 4. Genetic drift • Bottleneck Effect- When large population is drastically reduced by a disaster and lowers variation. Also narrows the gene pool. • famine, natural disaster, loss of habitat… • loss of variation by chance event • alleles lost from gene pool • not due to fitness

10. 5. Natural selection • Survival & reproduction due to changing environmental conditions. • climate change • food source availability • predators, parasites, diseases • toxins • combinations of allelesthat provide “fitness” increase in the population • adaptive evolutionary change

11. Mutation Gene Flow Non-random mating Genetic Drift Selection 5 Agents of evolutionary change