What Darwin Never Knew

1. What Darwin Never Knew How Genetics influences Evolutionary Thought

2. Video Clip Variation Darwin got right Darwin's idea has stood the test of time Recombination & Mutation

3. Natural selection

4. Sources of Variation Mutation Asexual or sexual reproducing organisms Can be beneficial, negative or neutral depending on environmental conditions the organism finds itself Recombination Gene shuffling through sexual reproduction This provides MOST of the heritable differences between generations In humans: 8.4 million different combinations of genes w/ 23 chromosomes

5. Evolution in terms of Genetics Species = individuals that can interbreed with viable offspring Share a common group of genes = gene pool Gene pool = all genes, all different alleles that are present in a population Relative frequency = number of times that allele occurs in a gene pool Usually a percentage NOTHING TO DO WITH DOMINANCE

6. Evolution in Genetic Terms Evolution = ANY change in relative frequency of alleles in a population

7. Traits Single gene = controlled by a single gene (two alleles) Remember that most genes have more than two options, so still a lot of variability Polygeneic = controlled by two or more genes (four or more alleles) Many possible genotypes

8. Traits Single Gene Natural selection on a single gene can lead to changes in allele frequencies –> industrial melanism Polygenic Effects of natural selection are more complex, affect the DISTRIBUTION of phenotypes

9. Selective Pressure Recall that selection causes some traits to survive and spread, while others are lost A selective pressure determines which traits are successful

10. Types of Selection

11. Selection pressures

12. Human Activity as Selective Pressure Human activity provides some of the strongest selection pressure in the world today Examples: Antibiotic Use & Resistance Habitat Destruction Over Hunting

13. Genetic Drift & Gene Flow Natural Selection is NOT the only source of change Alleles can become more or less common by chance Remember that genetics is a game of chance & probability Smaller populations are more affected by this (smaller gene pool)

14. Genetic drift

15. Factors affecting the gene pool

16. Random Changes in Genetic Drift Founder Effect When a new population is formed from a subset of a larger one, there will be changes in allele frequency See example slide.

17. The founder effect

18. Random Changes in Genetic Drift Bottleneck Effect Occurs when a large, genetically diverse population is drastically reduced by a catastrophic, non-selective event. Genetic diversity of survivors is likely to be much lower than that of the original population, even as a population reestablishes itself this low diversity is maintained Cheetahs

19. Speciation Natural selection CAN change the relative frequencies of alleles Can lead to speciation = changes in a species' gene pool that can create a reproductive isolation between the groups; creating a separate species

20. Types of Speciation Behavioral Isolation 2 populations can interbreed but have differences in courtship or other reproductive strategies

21. Types of Speciation Geographic Isolation 2 populations are separated by geographic barriers Mountains, rives, etc.

22. Types of Speciation Temporal Isolation 2 populations reproduce at different times

23. Types of Evolution Microevolution Any change in allele frequency over a long period of time Macroevolution Large scale evolutionary pattern or process change over a longer period of time

24. Patterns of Macroevolution Divergent Evolution Convergent Evolution Coevolution

25. Patterns: Divergent Evolution Two or more related species become more and more dissimilar

26. Patterns: Convergent Evolution Unrelated species become more and more similar as they become adapted to similar environments Recall analogous structures

27. Patterns: Coevolution 2 species evolve in response to changes in each other over time Insects & flowering Plants Mammals & Flowering Plants Predator & Prey – CLIP Parasites & Hosts