1. The document summarizes key ideas and evidence related to Charles Darwin's theory of evolution by natural selection, including his observations and ideas that led to developing the theory in his 1859 book On the Origin of Species. 2. Darwin noted that species are related through common ancestry (descent with modification) and proposed that natural selection is a mechanism driving adaptive evolution as individuals with heritable traits better suited to their environment tend to leave more offspring. 3. Evidence that has accumulated in support of evolution includes observations of natural selection today, the fossil record showing changes over time, anatomical and genetic similarities between organisms, and patterns of species distributions.

1. Mechanisms of Evolution AP Biology Chapter 22

2. Endless Forms Most Beautiful A new era of biology began in 1859 when Charles Darwin published The Origin of Species The Origin of Species focused biologists’ attention on the great diversity of organisms Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

3. Darwin noted that current species are descendants of ancestral species Evolution can be defined by Darwin’s phrase descent with modification Evolution can be viewed as both a pattern and a process pattern - data accumulated process - mechanisms in place to cause change

4. Fig. 22-2 American Revolution French Revolution U.S. Civil War 1900 1850 1800 1750 1795 1809 1798 1830 1831–1836 1837 1859 1837 1844 1858 The Origin of Species is published. Wallace sends his hypothesis to Darwin. Darwin begins his notebooks. Darwin writes essay on descent with modification. Darwin travels around the world on HMS Beagle . Malthus publishes “Essay on the Principle of Population.” Lyell publishes Principles of Geology . Lamarck publishes his hypothesis of evolution. Hutton proposes his theory of gradualism. Linnaeus (classification) Cuvier (fossils, extinction) Malthus (population limits) Lamarck (species can change) Hutton (gradual geologic change) Lyell (modern geology) Darwin (evolution, natural selection) Wallace (evolution, natural selection)

5. The Greek philosopher Aristotle viewed species as fixed and arranged them on a scala naturae The Old Testament holds that species were individually designed by God and therefore perfect

6. Carolus Linnaeus interpreted organismal adaptations as evidence that the Creator had designed each species for a specific purpose Linnaeus was the founder of taxonomy , the branch of biology concerned with classifying organisms

7. The study of fossils helped to lay the groundwork for Darwin’s ideas Fossils are remains or traces of organisms from the past, usually found in sedimentary rock, which appears in layers or strata

8. Fig. 22-3 Younger stratum with more recent fossils Layers of deposited sediment Older stratum with older fossils

9. Paleontology, the study of fossils, was largely developed by French scientist Georges Cuvier Cuvier advocated catastrophism, speculating that each boundary between strata represents a catastrophe

10. Geologists James Hutton and Charles Lyell perceived that changes in Earth’s surface can result from slow continuous actions still operating today. He called his ideas gradualism. Lyell’s principle of uniformitarianism states that the mechanisms of change are constant over time This view strongly influenced Darwin’s thinking

11. Lamarck hypothesized that species evolve through use and disuse of body parts and the inheritance of acquired characteristics The mechanisms he proposed are unsupported by evidence However, he did come up with a mechanism for evolution.

12. About Darwin As a boy and into adulthood, Charles Darwin had a consuming interest in nature Darwin first studied medicine (unsuccessfully), and then theology at Cambridge University After graduating, he took an unpaid position as naturalist and companion to Captain Robert FitzRoy for a 5-year around the world voyage on the Beagle

13. His interest in geographic distribution of species was kindled by a stop at the Galápagos Islands near the equator west of South America

14. Fig. 22-5 NORTH AMERICA EUROPE AFRICA AUSTRALIA GREAT BRITAIN SOUTH AMERICA ATLANTIC OCEAN PACIFIC OCEAN Cape of Good Hope Tierra del Fuego Cape Horn Tasmania New Zealand Andes Equator The Galápagos Islands Pinta Marchena Genovesa Santiago Daphne Islands Pinzón Fernandina Isabela San Cristobal Santa Fe Santa Cruz Florenza Española

15. Fig. 22-6 (a) Cactus-eater (c) Seed-eater (b) Insect-eater

16. In 1844, Darwin wrote an essay on the origin of species and natural selection but did not introduce his theory publicly, anticipating an uproar In June 1858, Darwin received a manuscript from Alfred Russell Wallace , who had developed a theory of natural selection similar to Darwin’s Darwin quickly finished The Origin of Species and published it the next year

17. Let’s get together on this so we can both be famous!

19. The Origin of Species Darwin developed two main ideas: Descent with modification explains life’s unity and diversity Natural selection is a cause of adaptive evolution In the Darwinian view, the history of life is like a tree with branches representing life’s diversity Darwin’s theory meshed well with the hierarchy of Linnaeus

20. Fig. 22-7

21. Fig. 22-8 Hyracoidea (Hyraxes) Sirenia (Manatees and relatives) Moeritherium Barytherium Deinotherium Mammut Elephas maximus (Asia) Stegodon Mammuthus Loxodonta africana (Africa) Loxodonta cyclotis (Africa) 0 10 4 2 5.5 24 34 Millions of years ago Years ago Platybelodon

22. Adaptations Darwin noted that humans have modified other species by selecting and breeding individuals with desired traits, a process called artificial selection Darwin then described four observations of nature and from these drew two inferences

23. Observation #1: Members of a population often vary greatly in their traits

24. Observation #2: Traits are inherited from parents to offspring Observation #3: All species are capable of producing more offspring than the environment can support

25. Observation #4: Owing to lack of food or other resources, many of these offspring do not survive My idea Precisely!

26. Inference #1: Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals Inference #2: This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations Favorable – NOT BEST NECESSARILY

27. Darwin was influenced by Thomas Malthus who noted the potential for human population to increase faster than food supplies and other resources

28. Individuals with certain heritable characteristics survive and reproduce at a higher rate than other individuals Natural selection increases the adaptation of organisms to their environment over time If an environment changes over time, natural selection may result in adaptation to these new conditions and may give rise to new species

29. Fig. 22-12 (b) A stick mantid in Africa (a) A flower mantid in Malaysia

30. Evidences for Evolution Direct observations The Fossil Record Homology Biogeography

31. 1. Direct Evidences Today Ex- Evidence of Drug-resistant HIV Ex – Evidence of Drug-resistant bacteria such as MRSA Ex – Evidence of Pesticide-resistant insects Coloration patterns in guppies due to predation

32. Fig. 22-14 Weeks Patient No. 3 Patient No. 2 Patient No. 1 Percent of HIV resistant to 3TC 0 0 25 50 75 100 2 4 6 8 10 12

33. 2. Fossil Evidence The fossil record provides evidence of the extinction of species, the origin of new groups, and changes within groups over time

34. Fig. 22-15 Bristolia insolens Bristolia bristolensis Bristolia harringtoni Bristolia mohavensis Latham Shale dig site, San Bernardino County, California Depth (meters) 0 2 4 6 8 10 12 14 16 18 1 2 3 3 3 1 2 4 4

35. Fig. 22-16 (a) Pakicetus (terrestrial) (b) Rhodocetus (predominantly aquatic) (c) Dorudon (fully aquatic) Pelvis and hind limb Pelvis and hind limb (d) Balaena (recent whale ancestor)

36. 3. Homology Homology is similarity resulting from common ancestry Can be both anatomical and molecular Anatomical similarities seen in comparative embryology suggest common ancestry

37. Homologous structures are anatomical resemblances that represent variations on a structural theme present in a common ancestor Fig. 22-17 Humerus Radius Ulna Carpals Metacarpals Phalanges Human Whale Cat Bat

38. Fig. 22-18 Human embryo Chick embryo (LM) Pharyngeal pouches Post-anal tail

39. Vestigial structures are remnants of features that served important functions in the organism’s ancestors Examples of homologies at the molecular level are genes shared among organisms inherited from a common ancestor

40. Examples of homologies at the molecular level are genes shared among organisms inherited from a common ancestor

41. Convergent evolution is the evolution of similar, or analogous, features in distantly related groups Analogous - having the same function but not necessarily evolutionarily related.

42. Fig. 22-20 Sugar glider Flying squirrel AUSTRALIA NORTH AMERICA

43. 4. Biogeography Darwin’s observations of biogeography , the geographic distribution of species, formed an important part of his theory of evolution Islands have many endemic species that are often closely related to species on the nearest mainland or island

44. Bird Biogeography

45. Is natural selection the ONLY mechanism responsible for evolution?