Industrial Melanism and Microevolution

1. Industrial Melanism and Microevolution

2. Microevolution of the fruit fly (Drosophila) species on the Hawaiian archipelago

3. Hierarchical Classification

4. Gene Flow additions to and/or subtractions from a population resulting in the movement of fertile individuals or gametes (rat snakes)

5. Gene Flow and Human Evolution Increasing migra- tion of people throughout the world has contributed to an increase in gene flow

6. Out of Africa Likely migration paths of humans out of Africa 10-20,000ya 10-20,000ya 50,000ya Many patterns of human traits reflect this migration

7. Variation & Natural Selection • Variation is the raw material for natural selection • there have to be differences within population • some individuals must be more fit than others

8. Mutation Gene Flow Non-random mating Genetic Drift Selection Five Agents of Evolutionary Change

9. Mutation & Variation • Mutation creates variation • new mutations are constantly appearing • Mutation changes DNA sequence • changes amino acid sequence • changes protein’s: • Structure • function • changes in protein may change phenotype & therefore change fitness

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

11. Genetic Drift occurs by chance when only certain members of a population reproduce and pass on their genes

12. Bottleneck Effect • When large population is drastically reduced by a disaster • famine, natural disaster, loss of habitat… • loss of variation by chance event • alleles lost from gene pool • not due to fitness • narrows the gene pool

13. Cheetahs • All cheetahs share a small number of alleles • less than 1% diversity • as if all cheetahs are identical twins • 2 bottlenecks • 10,000 years ago • Ice Age • last 100 years • poaching & loss of habitat

14. Northern Elephant Seals Hunted to nearly extinction in the late 1800s for their oil.

15. Polydactylism in the Amish Population Founder Effect: migration of a small subgroup of the population; a type of genetic drift

16. Amish Country: Lancaster County, Pennsylvania

17. One Room Schoolhouse -Amish Country: Lancaster County, PA

20. Founder Effect in Amish Ellis-van Creveld Syndrome Causes dwarfism and polydactyly

21. 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

22. The evolution of fruit fly (Drosophila) species on the Hawaiian archipelago (Founder Effect)

23. Natural Selection is the primary mechanism of adaptive evolution • Out of all the factors that can affect a gene pool only natural selection is likely to adapt a population to its environment

24. Mapping Malaria and the Sickle-Cell Allele This is a good example of heterozygote advantage.

25. Modes of Selection

26. Directional Selection

27. Evolution of the Horse over 50 million yrs

28. Hyracotherium American Museum of Natural History

29. Orohippus Note the toes!

30. Directional selection for beak size in a Galápagos population of the medium ground finch

31. Stabilizing Selection

33. Cepaea Snails Disruptive Selection

34. Disruptive Selection The curve has two peaks; dark shells appear in most forested areas whereas light-banded shells appear in areas of low lying vegetation Ex – When Cepaea snails vary because a wide geographic range causes selection to vary

35. Disruptive or Diversifying Selection Small-billed birds feed on soft seeds; large- billed birds feed on hard seeds (Black- bellied Seed Crackers – Cameroon, Africa)

36. The Two-Fold Disadvantage of Sex

37. Types of Selection • Most traits are polygenic - variations in the trait result in a bell-shaped curve • Three types of selection occur: • Directional Selection – the curve shifts in one direction ex: resistance to antibiotics by bacteria

38. Why Natural Selection Cannot Fashion Perfect Organisms • Evolution is limited by historical constraints. 2) Adaptations are often compromises. 3) Chance and natural selection interact. 4) Selection can only edit existing variations.

39. Natural selection can affect the distribution of phenotypes in three ways. They are: _______________ selection _______________ selection and _______________ selection.

40. A small population of organisms is suddenly cut off from the others in the population. This is knownas the _____________ effect. A small group of organisms migrates from one area to another. There is not a wide variation in the gene pool. This is known as the ___________ effect.

41. Types of Selection • (2) Stabilizing Selection • Ex - when human babies with low or high birth weight are less likely to survive