Mechanisms of Evolution

1. Mechanisms of Evolution

2. The Galapagos Islands: Darwin notes: • Island species varied from the mainland species, and island-to-island • Each island had either long or short necked tortoises depending on the island's vegetation

3. The Galapagos Islands: • Darwin noted: • Finches: Bill shapes are adaptations to different means of gathering food.

4. Galapagos finch species varied by nesting site, beak size, and eating habits

5. Outine: 4 Mechanisms of Evolution Natural Selection Mutation Migration/Gene Flow Genetic Drift, Founder effect, and Bottlenecking

7. #1 Natural Selection: Natural Selection – A gradual, non-random process by which biological traits become either more or less common in a population

8. Genetic Variation: Genetic differences within a population. The genetic variation in this scenario are the genes that code for the color of the beetle.

9. The logic of natural selection on graphic form

10. In these next few slides: Red=before natural selection Blue=after natural selection

11. 3 Types of Natural Selection that Act on Variation: 1. Stabilizing – natural selection that favors average individuals

12. 3 Types of Natural Selection that Act on Variation: 2. Directional selection – natural selection that favors an extreme form of a trait

13. 3 Types of Natural Selection that Act on Variation: 3. Disruptive selection – individuals w/ either extreme form of a trait

14. What is the bird going to eat?

15. Which butterflies will be selected against?

16. Summary:

17. Deep in the ocean there are many sea horses being hunted by dangerous fish with a strong hunger for large sea horses. Small seahorses are also being consumed by the thousands. What would the natural selection graph look like for this scenario? a. What size organism is being favored as the most fit for this enviornment? b. Draw the natural selection graph for this scenario? c. What type of natural selection is this considered?

18. #2 Mutation EX: A mutation causes two green beetle parents to have a brown beetle Mutation: change in a gene; alteration of a nucleotide sequence.

19. #3 Migration Gene Flow – transfer of alleles from one population to another. This increases genetic variation within populations Migration: Movement of some individuals to another population

20. #4 Genetic Drift Genetic Drift: some individuals may by chance (random) and not because of “fitness” leave more descendants and therefore pass on their genes.

21. Bottle Necking: quick reduction of a population that can affect gene frequency.

22. Founder effect: loss of genetic variation when a new population is started.

23. Genetic Driftsome individuals may by chance, and not because of “fitness,” leave more descendants and therefore pass on their genes Founder Effect Bottleneck • a new colony is formed by a few members of the original population • having an event that kills off members of a species randomly by chance.

24. So how do new species come about?

25. The Evolution of Species: • Species – group of organisms that can interbreed and produce fertile offspring. • Speciation – evolution of a new species. *NOTE: Organisms within the same species have reproductive success (ability to pass genes onto the next generation in a way that they too can pass on those genes.) Mule He can not have offspring because his parents are two different species  Donkey Horse + =

26. Physical Barriers Cause Speciation: 1. Allopatric Speciation aka Geographic Isolation – a physical barrier divides a population

27. Common ancestor of all canines (wolves, dogs, foxes) believed to have been part of a single population on Pangaea. After the continents split, isolated populations adapted in various ways that coincided with their habitats. This process known as geographic isolation can lead to new evolved species (or speciation!) Geographic Isolation

28. 2. Sympatric Speciation aka Reproductive Isolation – developing different mating seasons, mating rituals, and reproductive structures These Bowerbirds have different mating seasons and rituals. These 2 factors contribute to Reproductive Isolation

29. Does evolution happen fast or slow?

30. Both!

31. Rate of Speciation • Gradualism: – idea that species originate through a gradual change of adaptations • Punctuated Equilibrium : things staying the same for a period of time then rapidly changing due to a catastrophic event

32. Punctuated Equilibrium

33. Gradualism

35. Genetics Determines Evolution: • Gene Pool – All the alleles in a populations genes. In other words every form of a trait

36. Genetic Equilibrium – allele frequency remains the same over generations • Populations in genetic equilibrium are not evolving • Factors that affects genes can affect equilibrium 1. Mutations [negative, positive] • Negative more than likely causes death • Positive may be beneficial

37. Trait Variations – differences in Organisms • Increases or decreases an organisms chance of survival • Inherited and controlled by alleles • Allelic frequencies in a populations gene pool will change due to natural selection

39. Patterns of Evolution

40. Patterns of Evolution • Divergent Evolution: one species turns into many new species in a relatively short time • Ex: Adaptive Radiation: ancestral species evolves into different species due to their different environments (niches).

41. Patterns of Evolution cont’d • 2. Convergent Evolution – distant related organisms evolve and share similar traits due to similar environments.

42. Patterns of Evolution cont’d • 2. Convergent Evolution – distant related organisms evolve and share similar traits.

43. Cladograms: used to show evolutionary history of traits

44. Cladograms continued…