1. Descent with Modification Chapter 22

2. Rise of Modern Biology A. Pre-Darwin Ideas Geology Larmark B. Charles Darwin Darwin Wallace

3. Evolution: Change over time A new era of biology began when Charles Darwin published On the Origin of Species by Means of Natural Selection He made two points in The Origin of Species:  Today’s organisms descended from ancestral species  Natural selection provided a mechanism for evolutionary change in populations Natural Selection: individuals with certain heritable traits leave more offspring EvolutionaryAdaptations : characteristics that enhance survival

4. Pre-Darwin Ideas Aristotle believed that all living forms could be arranged on a ladder (scala naturae) of increasing complexity with every rung taken with perfect, permanent species. In the 1700’s, the dominant philosophy, natural theology  the Creator had designed each species for a purpose. Carolus Linnaeus, a Swedish botanist, developed taxonomy, a system for naming species and grouping species into a hierarchy of increasingly complex categories

5. Geology and the Gift of Time Idea that the earth is young (6000yrs)  never go anywhere Geologists  can’t get young earth Georges Cuvier (1769-1832) James Hutton (1726-1796) Charles Lyell (1797-1875)

6. Georges Cuvier(1769-1832) Paleontology  the study of fossils, Documented the succession of fossil species in the Paris Basin  Recognized that extinction had been a common occurrence in the history of life Catastrophism  instead of evolution that boundaries between strata were due to local flood or drought that destroyed the species then present  Later, this area would be repopulated by species immigrating from other unaffected areas

7. James Hutton (1726-1796) Scottish geologist Proposed that the diversity of land forms (e.g., canyons) could be explained by mechanisms currently operating A theory of gradualism  profound change results from slow, continuous processes  Same forces have always been there  erosion

8. Strata of sedimentary rock at the Grand Canyon From 1.25 BY to 250my

9. Charles Lyell (1797-1875) Scottish, friend of Darwin, good writer Proposed a Theory of Uniformitarianism  The geological processes had not changed throughout Earth’s history  Same processes are operating today as in the past

10. Jeane Baptiste Lamarck (1744- 1829) 1 st comprehensive idea of evolution Came up with the mechanisms for evolution  Use and Disuse  Inheritance of Acquired Characteristics  Stressed adaptation

11. Influence on Darwin Hutton’s and Lyell’s observations and theories had a strong influence on Darwin First, if geological changes result from slow, continuous processes, rather than sudden events, then the Earth must be far older than the 6000 years Second, slow and subtle processes persisting for long periods of time can add up to substantial change

12. The historical context of Darwin’s life and ideas

13. Charles Darwin Son of a wealthy physician Sent to become one Decided it was not for him Entered the clergy  studied natural theology-imprint of God in nature Professor recommends to go on a trip around the world Journey on the HMS Beagle  Mission was to chart the poorly known stretches of the South American coastline  He collected thousands of specimens of the exotic and diverse flora and fauna of South America

14. Darwin’s Observations The plants and animals of South America were very distinct from those of Europe Organisms from temperate regions of South America were more similar to those from the tropics of South America than to those from temperate regions of Europe South American fossils more closely resembled modern species from that continent than those from Europe. While on the Beagle, Darwin read Lyell’s Principles of Geology  Lead him to doubt the church’s position that the Earth was static and only a few thousand years old  He came to the conclusion that the Earth was very old and constantly changing By 1840, he had worked out the major features of a theory based on his observations from his journey Was hesitant to publish his ideas and was scared of the backlash that they would cause It wasn’t until he heard that another scientist, Alfred Russell Wallace, was developing a theory very similar to his own that he decided to publish.

15. Darwin and Wallace Alfred Wallace  independently developed a theory of evolution by natural selection Both share the idea of Natural selection as a Mechanism of evolution “It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is the most adaptable to change.”-Charles Darwin

16. Information that influenced Darwin Charles Lyell  geologist proposed that the Earth was very old and had slowly been changing for millions of years Thomas Malthus  economist  social problems as a result of the exponential growth of the human population Artificial selection by breeders

17. Artificial Selection

18. Darwin’ Two Main Ideas Descent with Modification Natural Selection and Adaptation

19. Descent with Modification All present day organisms are related through descent from unknown ancestors in the past Descendents of these ancestors accumulated diverse modifications or adaptations that fit them to specific ways of life and habitats The history of life is like a tree with multiple branches from a common trunk Closely related species, the twigs of the tree, shared the same line of descent until their recent divergence from a common ancestor

20. This evolutionary tree of the elephant family is based on evidence from fossils. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

21. Darwin’s Key Observations 1. Fossils & fossil records show that organisms  simpler  complex 2. Overproduction of offspring 3. Limited supply of resources in an environment 4. Survival in a limited environment depends in part on features inherited from parents

22. Natural Selection Individuals whose inherited characteristics adapt them best to their environment are most likely to survive and reproduce Basic Mechanism of Evolution  Natural Selection

23. Natural Selection and Adaptation Variations exist Many of these variations are heritable

25. Camouflage  Evolutionary Adaptation A heritable trait that increases an organism’s likelihood of surviving and reproducing in its environment

26. Evolution by Natural Selection Natural selection is the differential reproductive success of among individuals Variations exist; some represent adaptive traits that increase reproductive success Many of these are heritable Over time, this can increase the adaptation of organisms to their environment Environmental changes may result in adaptation of a species to these new conditions.

27. Fitness Individual organisms are selected Populations evolve! Remember, individuals live or die. They do not evolve!

28. Natural Selection in Action

29. Biston betularia : peppered moth

32. Evolution of Drug Resistant HIV 3TC interferes w/ reverse transcriptase

33. Evolution of Drug Resistance A drug does not create a resistant pathogen It selects for existing resistant pathogens And so with evolution: Evolution does not create novel life forms Nature selects from existing variants

34. Evidence of Evolution

35. 1. Fossil Records 2. Comparative Anatomy 3. Embryonic Structures 4. DNA Homology 5. Biogeography

36. Fossils Remains, traces or imprints of an organism preserved in the earth’s crust  Imprint  Mold  Cast  Petrified

37. Fossil Records 1. Fossils & the order in which they appear in layers of rocks 2. Fossil records show that animals & plants have appeared in a historical sequence, fossils found in rocks of different ages differ because life on Earth has changed through time

38. Each Layer represents a particular time period

39. Comparative Anatomy The comparison of body structures in different species Homologous Structures Analogous Structures Vestigial Structures Ex: common descent  evident in anatomical similarities between species in the same taxonomic group

40. Homologous Structures Structures that are similar & have been derived from a common ancestor, but have been adapted to different functions. ex: humans, cats, whales, bats  all mammals Whales’ flipper does not have the same function as a bat’s wing

41. Homologous Structures

42. Analogous Structures Body parts similar in function but have different structures Ex: wings of insects and birds

43. Vestigial Structures Body parts reduced in size & appear to serve no function

44. Embryonic Structures Embryos of closely related organisms often have similar stages in development

45. DNA Homology Comparison of genes and proteins shows the relationships between species

46. Biogeography Closely related species tend to be found in the same region  The geographical distribution of species only makes sense in light of evolutionary past What are specific examples?  Marsupial Mammals in Australia  Finches in Galapagos  Fruit flies in Hawaii

47. Different geographic regions, different mammalian “brands”