Evolution and the History of Life

1. Evolution and the History of Life MLK Fall 2005 M.Elizabeth www.marric.us/teaching

2. Chapter 8.1 Change Over Time • Differences Among Organisms • Do Species Change Over Time • Evidence of Evolution: The Fossil Record • Fossils • Reading the Fossil Record • Gaps in the Fossil Record • Vestigial Structures • Case Study: Evolution of the Whale • Evidence of Evolution: Comparing Organisms • Comparing Skeletal Structures • Comparing DNA from Different Species • Comparing Embryonic Structures

3. Changes Over Time • Differences between species relate to adaptations. • Adaptations – a hereditary characteristic (attribute) that helps an organism survive and reproduce in its environment. • Physical adaptations are heredity. Which means that the organism has no choice about the characteristics. • Emotional, cultural, and behavioral adaptations are choices that humans can make.

4. It’s all about Species • What is a Species? • A population of organisms that can mate with one another produces fertile offspring. • Example: Horses, Donkeys, and Mules • Breeding a male donkey to a female horse results in a mule; • Breeding a male horse to a female donkey produces a hinny = + Sterile Mule Horses and Donkeys are separate species

5. Do Species Change Over Time The Earth is very old – 4.6 Billion Years • The Earth was formed approx. 4.6 bya • The oldest rock is 3.5 Billion years • Fossil evidence suggests that species have changed over time because younger fossils are different, yet similar to older fossils.

6. Evolution • Evolution is the process by which populations of organisms acquire and pass on unique traits from generation to generation, affecting the overall makeup of the population and potentially leading to new species.

7. Four distinct mechanisms generate evolution (change in allelic frequency in populations over time): 1. mutation 2. gene flow 3. genetic drift 4. selection (natural and “artificial”)

8. Gene flow = movement of alleles from one population to another, which may change the allele frequencies • Gene flow can happen in several ways; in reality, usually a combination of them • individuals leave a population, taking their alleles with them • individuals join a population, introducing new alleles (or more copies of ones already present) • individuals in the population mate with outsiders, but the offspring stay in the population • this introduces new alleles (or additional copies of ones already present), because half of the offspring's alleles are from the outsider

9. Gene flow essentially moves alleles between populations • this tends to make neighboring populations similar to each other • because they exchange alleles and individuals in each have ancestors from the other • gene flow can take a mutation in one population and spread it throughout the world

10. the more migration or interbreeding occurs between two population, the more rapidly they become similar gene flow is important because it explains how a species like humans can be essentially the same all around the world Gene Flow

11. Genetic Drift • Genetic drift = change in allele frequencies due to chance • how it works • in any random process, like flipping a coin, we can predict the odds of any given outcome, but we can't predict which specific outcome will occur in any given case • Genetic Drift has a greater effect on smaller populations than larger populations.

12. In large populations, drift will not have much effect • just as when you flip a coin 1000 times, you expect to get fairly close to 500 heads • but the smaller the population, the more this random sampling error will change allele frequencies every generation • just as when you flip a coin only 4 times, you are not surprised at all to get 75% heads, or even 100% heads

13. Geologic Time Notations ya – Years Ago mya – Million of years ago bya – Billion years ago Precambrian Paleozoic ERA Mesozoic ERA Cenozoic ERA

14. Era word roots • Geologist use the clues in some of these words. • For example: • zoic refers to animal life • paleo means ancient • meso means middle, • ceno means recent. • So the relative order of the three youngest eras, first Paleoozoic, then Mesozoic, then Cenoozoic, is straightforward.

15. Evidence of Evolution: The Fossil Record • Fossils • Reading the Fossil Record • Gaps in the Fossil Record • Vestigial Structures

16. Fossils • Are found in the earth’s crust – the very uppermost part of the earth that is exposed to the surface or lying immediately below the oceans.

17. The Best Crust for Fossils • Sedimentary Rocks are the best crust for fossil formations; Example: The Grand Canyon. Strata = Layers of sediment so its called sedimentary rock

18. Rocks contain clues to the Earth’s past.

19. What are Fossils • Fossils are the mineralized remains of animals or plants or other traces such as footprints. • All of the fossils and their placement in rock formations and sedimentary layers (strata) is known as the fossil record. • The study of fossils is called paleontology.

21. What kind of rock is this? Sedimentary Rock

22. Law of Superposition:Youngest on Top • An undeformed sedimentary rock layer is older than the layers above it and younger than the layers below it D C B A

23. Law of Superposition • In terms of Relative Age • Rock Layer B must be younger than Rock Layer A • but Rock Layer B is older than Rock Layers C and D. D C B A

24. Once the order of formation is known, a RELATIVE AGE can be determined for each rock layer http://pubs.usgs.gov/gip/fossils/

25. Gaps in the Fossil Record • Occur because specific conditions are needed for fossils to form • Organisms with hard body parts (skeletons) are more likely to form fossils than organisms with soft body parts. Basic to this is the organisms cannot be eaten before fossilization • Find shells and bones • Fossils form best without oxygen – why peat bogs and tar pits have great fossils. Burial by sediments reduce oxygen exposure. • Freezing also allows fossil formation – Mammoth that Japanese scientists are trying to clone from DNA extracted from frozen Mammoth fossil. • Fossils once formed must not be destroyed.

26. Sea shells embedded in marine rock near Santa Cruz Ammonites near Redding

27. Human Remains

28. Vestigial Structures • Mammals are warm blooded vertebrates • Vestigial structures are organs that have no apparent function. • Examples: • Human appendix – narrow tube attached to the large intestines • Chimpanzee, gorilla, and orangutan appendix is functional and used to help digest tough plant material

29. Appendix

30. Whale evolution(terrestrial to aquatic in ~ 8 Myr) 8 million years total

31. PBS Whale Evolution http://www.pbs.org/wgbh/evolution/library/03/4/l_034_05.html One structural remnant (remaining part) of this evolutionary process are hind limb bones. These bones are called vestigial structures.

32. Evidence of Evolution: Comparing Organisms • Comparing Skeletal Structures • Comparing DNA from Different Species • Comparing Embryonic Structures

33. Comparing Skeletal Structures • Homologous Structures • Having similar origins and anatomical patterns • Examples – bird wings, human arms, whale flippers, bat wings, cat legs.

34. Homologous Structures

35. Analogous Structures • Analogous structures do the same thing – similar function, but different anatomy. • Wings (butterfly external skeleton, bat internal skeleton • Analogous structures: wing of an insect, bird, bat and pterosaur

36. Comparing DNA from Different Species • The actual molecular characteristics of DNA is measured and compared to other organisms. • There are four different nucleotides in DNA (Adenine, Guanine, Cytosine, and Thymine). • Gene sequencing – sections of DNA are sequenced for the order of nucleotide bases (ATCG or ATGC or ACTG, etc).

39. What We've Learned So Far • By the Numbers:What Does the Draft Human Genome Sequence Tell Us? • The human genome contains 3164.7 million chemical nucleotide bases (A, C, T, and G). • The average gene consists of 3000 bases, but sizes vary greatly, with the largest known human gene being dystrophin at 2.4 million bases. • The total number of genes is estimated at 30,000 —much lower than previous estimates of 80,000 to 140,000. • Almost all (99.9%) nucleotide bases are exactly the same in all people. • The functions are unknown for over 50% of discovered genes.

40. Looking for Relatedness

41. Crime Solving: The COmbined DNA Index System, CODIS, blends computer and DNA technologies into a tool for fighting violent crime.

42. Comparing Embryonic Structures • Ontogeny: Development of the Individual from conception to death. • Phylogeny: Development of the Species. • Vertebrate organisms (those having a backbone) have similar stages of life as an embryo

43. Open Court Publishing Company

44. Chapter 8.2 How Does Evolution Occur • Charles Darwin • Darwin’s Excellent Adventure • Darwin’s Finches • Darwin Does Some Thinking • Darwin Learned from Farmers and Animal and Plant Breeders • Darwin Learned from Geologists • Darwin Learned from the Work of Thomas Malthaus • Natural Selection • More Evidence of Evolution (DNA Mutation)

45. Darwin’s Excellent Adventure • HMS Beagle – Galapagos Island Travels • Galapagos Islands are part of the country of Ecuador though the islands are about 1,000 kilometers west of the continent of South America in the Pacific Ocean. There are 19 volcanic islands with a land area of 8,000 km2 in an area of the Pacific Ocean over 60,000 km2 About Darwin http://www.aboutdarwin.com/timeline/time_01.html

46. Darwin’s Finches

47. Diversity • Darwin saw finches that were very different from each other as he traveled to the various islands of the Galapagos. • Because of their physiological differences (beak shapes), the finches had very different diets

48. The diversity of life… Although there is unity in life there is also a great deal of diversity! Estimates of Diversity: ~1.7 million cataloged species 50,000 vertebrates 260,000 species of plants 750,000 species of insects Total diversity  5-30 million species !

49. Darwin Does Some Thinking • Darwin wonders how did the finches become so different. He thought maybe there was a storm that separated the original population resulting in geographic isolation (one of the ways that speciation can occur)

50. Darwin Learned from Farmers and Animal and Plant Breeders • Darwin was very familiar with artificial selection or better known as selective breeding. • Certain traits are determined by the breeder to be favorable. If only those organisms with the favorable traits are breed then the trait will occur more often in the population. By isolated certain individuals the differences can grow.