Natural Selection & Evolution

1. Natural Selection & Evolution

2. Evolution • Evolution is defined as the change in a population over time • This is not a change in an individual (like weight loss) but in a population due to inherited factors • A population is a group of members of the same species living in the same area, reproducing together

3. Macroevolution—how different species are related (and how new species can be created) “descent with modification” As evidenced by tracing homologous and vestigial structures Microevolution—evolution within a species (small group) Kettlewell’s moths would be an example of this Types of Evolution

4. Fossil Record Comparative Anatomy Comparative Embryology Molecular Biology Law of superposition Homologous structures Vestigial structures Stages of fetal life Gene sequencing Amino acid sequencing Evidence for Evolution

5. Can tell us how old things are relative to other fossils Not everything makes a good fossil Not every environment is good for fossil preservation Gaps in the fossil record hold questions Because there is so much fossil evidence, it is basis for evolutionary thought Fossil Record

6. Trilobites: an extinct arthropod • Diverse group of extinct arthropods (exoskeleton and joint appendages) • Used to date rock formations • First appeared in the fossil record 521 mya and lived for 270 million years.

7. Show us how things may have evolved from one basic plan/blueprint geared toward a function Called descent with modification Homologous Structures

8. Can show us connections to other organisms with similar functional organs Can help us trace our evolutionary history (what we once were like) Ex: human tailbones, wings on flightless birds, wisdom teeth, human appendix http://www.livescience.com/11317-top-10-useless-limbs-vestigial-organs.html Vestigial Structures

9. Can show us how a variety of organisms are more distantly related Even if they don’t look alike as adults, they may have stages as embryos/fetuses that show a common link/ancestor Comparative Embryology

10. Includes comparing the gene sequencing and amino acid sequencing of proteins of organisms to see how much they have in common This is one of the strongest types of evidence for evolution theory Molecular Biology

11. A branched diagram representing ancestral relationships between organisms A visual evolutionary tree of life Is now often based on molecular biology evidence (gene and amino acid sequencing) Cladograms

12. Cladograms

13. Gradualism Small amounts of change over a very long period of time Darwin’s theory (‘descent with modification’) Fossil record Punctuated Equilibrium Dramatically large amounts of change over a very short period of time Explains unusual gaps in the fossil record (dinosaur/asteroid) Macroevolution

14. Gradualism vs. Punctuated Eq.

15. Convergent evolution When two populations living in similar conditions become more and more similar Cactus in deserts across the globe look similar due to similar conditions and survival needs Divergent evolution When two populations living in very different conditions become increasingly different Darwin’s finches that migrated to different coastal islands, all required slightly different beaks to get food Microevolution

16. The evolutionary process by which new species arise Species are groups of individuals that successfully mate together Can be due to a variety factors, either physical or behavioral barriers Geographic Isolation Reproductive Isolation Speciation

17. When members of a group are physically isolated and therefore no longer reproduce together It can also be that the two subgroups are still physically close to each other, but do not interbreed due to subtle differences in their habitats Geographic Isolation

18. Temporal isolation: members have different breeding times Behavioral Isolation: members are not attracted to other members for mating (ex. Courtship ritual) Mechanical Isolation: the members are not physically able to mate Reproductive failure: members do mate and a pregnancy occurs/offspring is created BUT the offspring are sterile (ex. A mule) Reproductive Isolation

19. Wrote On The Origin of Species Is credited with the theory of natural selection as the primary way we explain how evolution occurs Shares partial credit with Alfred Wallace Darwin

20. He was greatly influenced by his trip to the Galapagos Islands off the coast of S. America He collected many specimens and detailed notes/made diagrams His 20 years of data is why he receives more credit than Wallace Lyell’s book detailing how land forms gradually change over time (Principles of Geology) and Malthus’ essay On the Principal of Population describing how populations competed for food and shelter Both books impacted Darwin’s work Darwin

21. Contacted Darwin about jointly presenting a paper describing the theory of natural selection He had arrived at the theory of natural selection independently (on his own) Darwin agreed so that he would not be forgotten in the development of this theory They both had taken trips to S. America and had read the same influential books Darwin receives more credit due to the detailed notes/evidence he had collected over many decades of study Wallace

22. The Theory of Natural Selection • Within every population exists variation • Positive variations are called adaptations • Individuals with beneficial adaptations live longer and therefore produce more offspring • More offspring will show the beneficial adaptation in the following generations “Survival of the Fittest”

23. Kettlewell’s Moths • Kettlewell studied the effects of pollution on typically light colored trees on a moth population • The moth population included light and dark colored moths

24. The term describes how the moth population changed over generations to adjust to the changing tree color environment This ‘current’ example of natural selection in action added to the strength of Darwin’s argument (not just fossils as evidence) Industrial Melanism

25. Directional selection involves the selection of one extreme of any given trait over the other forms of the trait. It occurs when an organism experiences a change in its environmental conditions. Types of Natural Selection

27. Stabilizing selection is the exact opposite of disruptive selection, as it favors the intermediate form of a trait against the extreme forms. It causes a reduction in the variation observed in the expression of that trait and allows the propagation of the intermediate, most adapted trait in the population. Over the course of time, this intermediate form becomes more and more common in the population, while the extreme forms become less common, till they are eventually lost. Types of Natural Selection

29. Disruptive selection, on the other hand, involves favoring the extreme forms of a trait against the intermediate forms, thereby dividing the overall population into two distinct groups. Its occurrence depends on various factors involved in the species-habitat interaction. Types of Natural Selection

31. You decide!

33. Gene flow—a change in a population due to migration of individuals in and out of the area https://evolution.berkeley.edu/evolibrary/article/evo_21 Non-random mating—how reproductive choices by individual members impact a population over time Genetic Drift--Bottleneck effect and Founder’s effect—how random chance impacts a small population Mutation—when a widespread genetic mutation impacts many members of a population (rare) Other mechanisms of evolution

34. Genetic Drift • Bottleneck and founder events are similar: they reduce the genetic diversity in a population. • The only difference between the two is the type of event that causes these effects. https://www.youtube.com/watch?v=W0TM4LQmoZY

35. Bottleneck Effect • Bottleneck Effect – a change in allele frequency due to a natural disaster that reduces the size of the population. • Earthquake • Tsunami • Fires • The original population has three types of alleles. • A bottleneck event occurred and the red alleles did not survive the natural disaster. • The surviving population now has only two types of alleles. There’s less genetic variation.

36. Founders Effect • Founder Effect – allele frequency changes due to a small group of the population migrating. • This small population makes up the founders of the new genetic pool. The founding individuals may carry alleles in a higher frequency than in the general population just by chance.