Theory of Evolution

1. Theory of Evolution Chapter 15

2. The Old Testament Traditional Christian beliefs state that all organisms resulted from the direct actions of a creator • Each organism has a specific role to play • Each was individually created by God • Each organism is such a perfect fit in its environment because it was “hand-crafted” for that environment. • The earth is about 6,000 years old • The universe is about 13,000 years old

3. Cuvier (1769-1832) 1. founder of paleontology (studied fossils – anatomist) 2. observed that different strata of sedimentary layers contained different fossils. 3. catastrophism--explained changes in animal world in terms of catastrophes that had destroyed whole populations of living things in prehistoric times (floods etc.)

4. Hutton(1726-1797) and Lyell (1797-1875) both were influential geologists Lyell a. Theory of uniformitarianism small forces acting over long periods of time can result in major changes e.g. destruction of mountains. b. great champion of Hutton's work c. historical and physical continuity of nature d. Principles of Geology (1830)--greatly influenced Darwin even though he himself did not admit biological evolution A COMBINATION OF LYELL’S AND HUTTON’S IDEAS IS EMPLOYED TODAY

5. Lamarck (1744-1829) • Believed that life appears from inanimate matter by spontaneous generation, and becomes more complex over time • changing environment alters the needs of the organisms • use and disuse alter morphology and is transmited to subsequent generations (inheritance of acquired characteristics) • Believed the earth was very old

7. Charles Darwin (1809-1882) Voyage of the H. M. S. Beagle (1831-1836) Made observations in Galapagos Islands and South America.

8. So What is Natural Selection?

9. What Darwin inferred from his observations • Overproduction of offspring: When there are more organisms than an environment’s carrying capacity… • Struggle for existence: there will be a struggle for survival a.k.a COMPETITION • Genetic Variation: The organisms that possess a variation that will help them in this struggle, will survive to reproduce. • Differential survival and reproduction: These favorable traits will be passed on to their offspring, giving them the same benefit.

10. Summing it up In the end, only those members of the population that are best adaptedto their environment will be successful. THIS WAS HIS THEORY OF NATURAL SELECTION http://www.pbs.org/wgbh/evolution/library/11/2/e_s_4.html

11. Lamarck versus Darwin / Wallace

12. Artificial Selection • Animal husbandry • Pet breeding Human beings select desired traits

13. Sexual Selection • A form of natural selection where individuals with certain inherited traits are more likely to finds mates. • Sexual selection causes sexual dimorphism, where there are clear differences between the two sexes (Like in human males and females)

14. Intrasexual Selection – Individuals of the same sex compete actively and sometimes aggressively for a mate from the opposite sex. Usually males display this behavior. Intersexual Selection – Individual selects a mate based on certain physical characteristics such as showy feathers, muscles, etc. Females usually follow this route.

15. Evidence of Evolution • Fossil Evidence • Anatomical Homologies • Embryological Homologies • Molecular Homologies • Vestigial Organs

16. Fossil Record • Sedimentary rocks are the richest source of fossils • As a result of these sedimentation periods, sedimentary rocks form strata • The deeper the stratum, the older and simple the organisms • The higher the stratum, the newer and more complex the organisms.

18. Anatomical Homologies Homologous structures indicate evolutionary ties

19. Analogy vs. Homology • Structures that are similar due to evolutionary origin, such as the forearm bones of humans, birds, porpoises, and elephants, are called homologous. • Structures that evolve separately to perform a similar function are analogous. The wings of birds, bats, and insects, for example, have different embryological origins but are all designed for flight.

20. The bones in the three flying animals (not the insect) are homologous, but the wing structures of all 4 flying animals are analogous

21. Embryological Homologies

22. Molecular Homologies • All life has DNA, RNA and the genetic code is universal • So all animals could have descended from a common ancestor • Even animals as dissimilar as bacteria and humans, share common genes inherited from a distant ancestor.

23. Vestigial Organs

24. Approximately 50 million years ago, this wolf-size pakicetid—an ancestor of the whale—lived on land but may have waded into streams to feed on fish. Fossil Record (basically anatomical homology) • Transitional fossils that link the past with the present Read article on origin of whales

25. When a population diverges from an original population and fills many parts of a new environment, it is called adaptive radiation. • Coevolution – when one species evolves, the other species that depends on it must also evolve to survive.

26. Adaptive Radiation

27. Population Genetics and Speciation Chapter 16

28. A population is a group of individuals in a certain time and place that belong to the same species – that is: they can interbreed and produce viable offspring • A Gene Pool is the total number of genes within a population at a particular time and place.

29. What causes variations? • Mutations in an original gene will give rise to new alleles. • Alleles will create the variations in a population that Darwin talked about • Some alleles will help an organism, others will harm it • The alleles that contribute to the survival of a species in a particular environment, will be passed on

30. Gene Pool • All the alleles in a population are collectively called the gene pool of that population

31. Get Out! The Pool is Closed! • The Amish for example – the only variations in the population arise from independent assortment and crossing over during meiosis and random fertilization within the community • No external agents – immigration, for example

32. Gene Flow • When alleles are introduced in or removed from a population it is called gene flow. This can happen due to: • Immigration • Emigration

33. Types of Natural Selection

34. Speciation • Speciation – the formation of a new species - Geographical isolation – when some members of a population become separated from the main population and eventually accumulated enough mutations to become a separate species. -Reproductive isolation – when 2 individuals can no longer reproduce together, they become separate species.

35. Allopatric Speciation Allopatric speciation of squirrels in the Grand Canyon (see Campbell fig. 24.7, p. 451). The canyon is a barrier to dispersal by small mammals, and as a consequence the isolated populations can diverge. •  First geographic isolation... • Unless populations are geographically isolated they will continue to interbreed • ...then genetic isolation • Populations diverge to the point where they no longer interbreed • This may be due to adaptation to different environments, or genetic drift

36. Gradualism vs. Punctuated Equilibrium

37. THE END