1. Drill Define Define TheoryTheory LawLaw HypothesisHypothesis

2. How did life begin?

3. Ideas as to the Origin of Life Extraterrestrials Extraterrestrials Divine Intervention (God) Divine Intervention (God) Oparin Hypothesis Oparin Hypothesis

4. Oparin Hypothesized about conditions on early earthHypothesized about conditions on early earth Known as primordial stew or soupKnown as primordial stew or soup No OxygenNo Oxygen Lots of NitrogenLots of Nitrogen MethaneMethane LightningLightning Ozone from lightningOzone from lightning Formed amino acids from his experimentFormed amino acids from his experiment

6. Background What is an organism? What is an organism? A living thing is an organism.A living thing is an organism. What is an offspring? What is an offspring? Your kids are your offspring. (babies)Your kids are your offspring. (babies) What is a species? What is a species? Two organism are the same species when they can have fertile offspringTwo organism are the same species when they can have fertile offspring Grizzly and a polar bearGrizzly and a polar bear What is a population? What is a population? Group of organisms of the same species.Group of organisms of the same species.

7. Where do new species come from?

8. Evolution Evolution is a set of ideas which explain how populations change over time. Evolution is a set of ideas which explain how populations change over time.

9. Evolution is NOT Origin of life Origin of life A law A law Opinion Opinion A hypothesis A hypothesis Directional Directional

10. Ideas Relating to Evolution Aristotle Aristotle Things are unchangingThings are unchanging Couvier Couvier Deeper Fossils are olderDeeper Fossils are older Deeper you go the more dissimilar fossils areDeeper you go the more dissimilar fossils are Lamarke Lamarke Use Disuse TheoryUse Disuse Theory GiraffeGiraffe Malthus Malthus Organisms make a lot of offspring (babies)Organisms make a lot of offspring (babies) Some will not survive.Some will not survive.

11. Nothing in biology makes sense except in the light of evolution. – Theodosius Dobzhansky Evolution as the Cornerstone of Biology Charles Darwin in later years

12. Darwin’s Global Circumnavigation of the Globe on the HMS Beagle Provided a Rich Source of Observations and Experiences A reconstruction of the HMS Beagle sailing off Patagonia.

14. Darwin’s Observations for Natural Selection 1: The number of organisms of each species will increase, generation to generation. (Malthus) 2: In nature, populations tend to remain stable in size. (Darwin) Production of more individuals than can be supported by the environment leads competition. Not everyone will live 3: Environmental resources are limited.

15. Darwin’s Observations and Inferences 4: Individuals of a population vary extensively in their characteristics with no two individuals being exactly alike. 5: Much of this variation between individuals is heritable.

16. Darwin’s Observations and Inferences So… Survival is not random, but depends the heritable characteristics of individuals. Individuals who inherit characteristics that make them good enough to survive are likely to leave more offspring.

17. Natural Selection Those best suited to the environment will survive. Those best suited to the environment will survive. Survival of the fit enough Survival of the fit enough

18. Forms of Natural Selection

19. Microevolution Change in the frequency of alleles in a population over generations (short time period) Change in the frequency of alleles in a population over generations (short time period)

20. Ketterwells Moths Industrial Revolution Industrial Revolution Darkened TreesDarkened Trees City moths observed to be darkerCity moths observed to be darker Country moths observed to be lighterCountry moths observed to be lighter Selection Pressure Selection Pressure Trees Darker in the city by Soot.Trees Darker in the city by Soot.

23. Evolutionary Time Scales Microevolution: Short time scale events (generation-to-generation) that change the genotypes and phenotypes of populations.

24. Initial population has rare resistant mutant Most cells are resistant Population expands in absence of antibiotic Surviving cells are all resistant After second round of antibiotic treatment population expands and all cells are resistant First round of incomplete antibiotic treatment Antibiotic treatment discontinued Second round of antibiotic treatment Evolution in Action - Antibiotic Resistance in “TB Bacteria”

25. Population Genetics Human phenotypic variation. Microevolution A population is a group of interbreeding organisms present in a location at a time.

26. Forces Which Cause Microevolution Natural Selection Natural Selection Mutation Mutation Gene Flow (Migration) Gene Flow (Migration) Genetic Drift Genetic Drift Non-Random Mating Non-Random Mating

27. Mutation Mutation is the only source of new alleles in a species. Mutation provides the raw material of evolution. Mutation acting alone works too slowly to drive evolution. With an average mutation rate, it takes ~ 70,000 generations, far more than the existence of modern humans, to reduce allele frequency by 50%.

28. Gene Flow or Migration Gene flow makes separate populations more similar genetically. The effects of gene flow are seen in many human populations. Gene flow in plants – wind-dispersed pollen moving between Monterey pines.

29. Genetic Drift Genetic drift is random fluctuation in allele frequency between generations. Its effects are pronounced in small populations.

30. Non-Random Mating If people over 6 feet tall only have offspring with people 6 feet tall a change in alleles is likely to happen If people over 6 feet tall only have offspring with people 6 feet tall a change in alleles is likely to happen

31. A Genetic Bottleneck Animals known to be affected by genetic bottlenecks include the northern elephant seal, cheetah, and some human populations. A genetic bottleneck is one form of genetic drift in which a population “crashes” then rebounds.

32. The Founder Effect The founder effect is another form of genetic drift in which a small portion of a population migrates to a new area then expands in number. The Founder effect accounts for the high frequency of Ellis-van Crevald syndrome in Amish, retinitis pigmentosa on Tristan da Cunha, and colorblindness on Pingelap. In this case, the allele frequencies in the expanded population are often very different from those of the founder population.

33. Inbreeding – One Form of Non-Random Mating Inbreeding occurs when related individuals mate. Inbreeding reduces the proportion of heterozygotes and increases the proportion of homozygotes in a population. This is a bad idea when considering recessive genetic disorders. Example: A mating between first cousins increases the risk of albinism 10-fold. Albinism – a recessive genetic condition. Inbreeding, genetic bottlenecks and founder effects all come into play in conservation genetics.

34. Evidence for Evoltuion

35. Evidence for Evolution? The fossil record Transitional forms in the evolution of whales.

37. Evidence for Evolution? Comparative anatomy Homologous structures in vertebrate limbs

38. Evidence for Evolution? Comparative embryology

39. What’s the Evidence for Evolution? Molecular biology

40. To be continued….

41. Darwin’s Observations and Inferences Inference 3: The unequal ability of individuals to survive and reproduce leads to a gradual change in a population, with favorable characteristics accumulating over generations. These three inferences are a statement of Darwin’s Theory of Evolution.

42. What is Evolution? The kind we’re talking about is sometimes called organic evolution to distinguish it from non-biological changes over time. Working definition: Evolution is the progressive change in organisms over time.

43. Natural selection produces organisms better adapted (more fit) to particular environments. What is Natural Selection? Natural selection is the process in which more fit organisms produce more offspring than less fit organisms. For natural selection to be of evolutionary significance, at least some of the superior fitness of parents must be heritable.

44. Evolution in Action - An Increase in DTT-Resistance Following the Institution of Spraying Programs

45. Evolutionary Time Scales Macroevolution: Long time scale events that create and destroy species.

46. Population Genetics and Microevolution The weak link in Darwin’s theory was understanding how traits were transmitted. The rediscovery of Mendel’s work and the development of population genetics in the first decades of the 20 th century greatly strengthened evolutionary theory, leading to the so-called synthetic theory of evolution.

47. Population Genetics and Evolution Taking a reductionist approach, evolution can be considered as changes in allele frequencies over time. What causes allele frequency change?

49. “Forces” of Allele Frequency Change Natural Selection The force that changes allele frequency so that a population becomes better adapted The force that changes allele frequency so that a population becomes better adapted

50. One force changes genotype frequency without changing allele frequency. This is: Non-random mating An Evolutionary Force That Does Not Change Allele Frequency

51. Natural Selection Natural selection leads to adaptation – an increase in the fitness of a population in a particular environment. Natural selection works because some genotypes are more successful in a given environment than others. Successful (adaptive) genotypes become more common in subsequent generations, causing an alteration in allele frequency over time and a consequent increase in fitness.

52. Stabilizing Selection of Human Birth Weight

53. Stabilizing Selection for the Sickle Cell Allele In heterozygous form, the sickle cell allele of  -globin confers resistance to malaria. Therefore, the allele is maintained, even though it’s harmful in homozygous form.

54. Directional Selection Hominid Brain Size

55. An Outcome of Strong Artificial Selection

56. Does Selection Create the Perfect Organism? No, only better organisms as evolution is constrained by history and buffeted by random events.

57. What is a species? The definition we’ll use – A species is a group of individuals capable of interbreeding to produce fertile offspring. This is the biological species concept. Like all attempts to define a species, it has many problems. Macroevolution and Speciation

58. How Do Species Arise? One important way is initiated by geographic separation of populations. This leads to reproductive isolation, which is the key force driving speciation.

59. Geographic Separation and Reproductive Isolation Two species of ground squirrel descended from a common ancestral population separated by the formation of the Grand Canyon.

60. There Are Many Different Mechanisms of Reproductive Isolation

62. Mass Extinctions Have Been a “Fact of Life” on Earth

63. The Dynamics of Speciation - Gradualism or Punctuated Equilibrium? A current debate is whether new species arise gradually at a constant rate or in bursts of speciation that may coincide with environmental change.