Evolution

1. Evolution

2. Spontaneous Generation living things come from nonliving things Disproven by: Redi Spallanzani Pasteur Where does life come from?

3. Francesco Redi’s Experiment Uncovered Flask = Maggots & Flies

4. Lazzaro Spallanzani’s Experiment

5. Louis Pasteur

6. So Then, How Did Life Begin On Earth? • Oparin’s Hypothesis • CH4 + NH3+ CO2 + H2O vapor + heat and light energy organic compounds

7. The Miller-Urey Experiment • Created conditions of Oparin’s hypothesis in a lab setting • Organic compounds, including amino acids, were formed

8. Isn’t That The Same As Spontaneous Generation? • No • Formation of life took a billion years • Spontaneous generation took 1-2 weeks • Formation of life required extreme heat and energy

9. How old is the Earth? • Earth = approximately 4.6 billion years old • Life began approximately 3.6 billion years ago

10. How Do We Know The Age of the Earth? • Radioactive Dating of Fossils & Rocks • Ex: Carbon-14, Uranium 238

11. Fossils • 2 methods of determining age – • Relative age – based on position in rock strata (layers) • Absolute age – based on radioactive dating

12. OK, so what were the first organisms on Earth? • Archaebacteria • Chemosynthetic (due to where they lived) – use inorganic molecules as source of energy instead of sunlight

13. The appearance of eukaryotes; or, the story of endosymbiosis • Endosymbiosis • Proposed by Lynn Margulis • Led to cells w/chloroplasts and mitochondria

14. Mass Extinctions • Throughout history, there have been five mass extinctions (mass extinction = over 50% of species on Earth died rapidly, due to meteor impact, Ice Age, etc.) • Some mass extinctions allowed new life forms to dominate the Earth • The last mass extinction allowed mammals to dominate the land.

15. How do organisms evolve? • 2 proposed hypotheses • Lamarck – acquired traits – use and disuse • Darwin – descent with modification due to natural selection

16. Jean Baptiste de Lamarck • Acquired traits are passed on to offspring Long necks from reaching for trees - passed on to offspring.

17. A Common Misconception

18. Charles Darwin

19. Two Important Influences On Darwin • Thomas Malthus • Human population growth is controlled by limited resources • Charles Lyell • Uniformitarianism – geologic processes occuring today are the same as they were millions and billions of years ago

20. Darwin’s Theory #1: Descent With Modification • New forms in fossil record = modified forms of ancestral species

21. Darwin’s Theory #2: Natural Selection • Environment limits growth of populations • Due to variations among individuals in a species, some members of a population compete better for limited resources, so they survive and reproduce, while others do not.

22. Notice The Variation In These Individuals Of A House Finch Population Some are more likely to survive and/or mate due to differences in coloration

23. Stabilizing Selection Directional Selection Disruptive Selection Nature selects the average form of a trait (human baby size) Nature selects one extreme form of a trait (e.g. only the very long tongue in anteaters, not the short tongue) Nature selects both the extreme forms of a trait (e.g. very bright shell and very dull shell) 3 General Types of Natural Selection

24. The 3 Types of Natural Selection Disruptive Selection Stabilizing Selection Directional Selection

25. Sexual Selection: A Special Type of Directional Selection • Individuals of one sex (usually males) of a species are more likely to get picked as partners by the other sex if their characteristics are bolder, brighter, louder or stronger than other members of the same sex.

26. Sexual Selection in Peacocks

27. Of Course, Being More Noticeable Does Have Its Disadvantages . . .

28. Other Factors Can Affect Genetic Variation In A Population • Other factors besides meiosis/sexual reproduction and mutations create the variation in the genetic material (gene pool) of a population on which natural selection acts • Migration • Assortative (nonrandom) mating = sexual selection • Genetic Drift

29. Genetic Drift • Change In Allele Frequency Caused By Random Chance • Random chance = natural disasters, disease, hunting, etc. • Has a greater affect on small populations • Often causes reduction in alleles (not always the weakest alleles) present in the gene pool.

30. The Bottleneck Effect • A direct result of genetic drift • As a result of some random event, several alleles are lost from a population when only a small number of individuals in the population survive to reproduce. • Northern Elephant Seals – pop. reduced to 20 individuals due to hunting in 1890’s. • Pop. rebounded to 30,000 now • Very little genetic variation

31. Hardy-Weinberg Equation • Mathematical equations used to determine if a population is evolving. • In order for no evolution (change in gene pool) 5 conditions: • Large population • No mutations • No genetic drift/natural selection • No migration • Random Mating • p = frequency of dominant allele • q = frequency of recessive allele • p + q = 1

32. Hardy-Weinberg • p2 = frequency of homozygous dominant individuals • 2pq = frequency of heterozygous individuals • q2 = frequency of homozygous recessive individuals • p2+ 2pq + q2 = 1 • In a population of 1000 individuals, 360 cannot taste PTC paper. Which value in the equation is that?

33. Evidence Of Evolution • Homologous Structures • Analogous Structures • Vestigial Structures • Embryological Similarities • Macromolecule (DNA, RNA, Proteins) Similarities

34. Homologous Structures • Similar features from a shared common ancestor

35. Analogous Structures • Similar features, but no shared common ancestor • Show that the environment selects for certain abilities.

36. Vestigial Structures • Show that organisms carry genes for structures that were useful in ancestors, but genes for these structures have been turned off in modern day organism. Human Vestigial Structures

37. Embryological similarities • Show genes organisms have in common. • These genes are used early in development, but turned “off” later.

38. Macromolecule Similarity • The more similar the DNA, RNA or proteins between two organisms, the more recently they shared a common ancestor.

41. Before We Go On, An Important Question: What is a species? • Members of a species are morphologically (physically) similar, and can successfully interbreed (produce fertile offspring).

42. How Do New Species Form? Speciation • Isolation • Isolating Mechanisms • Prezygotic Isolation • Postzygotic Isolation

43. Geographic Isolation • Physical separation of members of a population (by formation of a canyon, mountain, river, etc.) • Leads to different adaptations on each side of barrier, and eventually new species (allopatric speciation)

44. Geographic Isolation = New Species: An Example 2 Species of Squirrels Formed When They Were Separated By The Grand Canyon

45. Prezygotic Isolating Mechanism #1:Temporal Isolation • Species isolated because they reproduce in different seasons or times of day • Prevents species from ever breeding together – keeps two species separate but usually arises after species have formed.

46. Prezygotic Isolating Mechanism #2:Behavioral Isolation • Species Differ In Their Mating Rituals (e.g. different bird songs, mating colors, dances, pheromones, etc.)

47. Prezygotic Isolating Mechanism #3Ecological Isolation • Ecological Isolation • Species inhabit the same area, but different habitats, so they don’t encounter each other

48. Prezygotic Isolating Mechanism #4: • Mechanical Isolation • Body structure prevents mating • In layman’s terms - the parts don’t fit Bush Baby

49. Bush Baby Isolating Mechanism

50. Prezygotic Isolating Mechanism #5 • Gametic Isolation • The sperm is unable to fuse with the egg.