Descent with Modification – A Darwinian View of Life

1. Descent with Modification – A Darwinian View of Life Chapter 22 A.P. Biology Liberty Senior High School Rick L. Knowles

2. Figure 1.17 • Concept 1.4: Evolution accounts for life’s unity and diversity • The history of life • Is a saga of a changing Earth billions of years old

3. Theodosius Dobzhansky “Nothing in biology makes sense except in the light of evolution.” The American Biology Teacher (1973)

4. Overview: Darwin Introduces a Revolutionary Theory • A new era of biology began on November 24, 1859 • The day Charles Darwin published On the Origin of Species by Means of Natural Selection Charles Darwin, 1831, age 22, starting his voyage on the HMS Beagle

5. Concept 22.1: The Darwinian revolution challenged traditional views of a young Earth inhabited by unchanging species • In order to understand why Darwin’s ideas were revolutionary • We need to examine his views in the context of other Western ideas about Earth and its life

6. The historical context of Darwin’s life and ideas Fig. 22.2

7. The Scale of Nature and Classification of Species • The Greek philosopher Aristotle • Viewed species as fixed and unchanging • The Old Testament of the Bible • Holds that species were individually designed by God and therefore perfect • “Intelligent Design”

8. Carolus Linnaeus • Interpreted organismal adaptations as evidence that the Creator had designed each species for a specific purpose • Was a founder of taxonomy, classifying life’s diversity “for the greater glory of God” • Viewed species similarities not as evolutionary relationship, but as patterns of creation. Carolus Linnaeus, 1707 -1778

9. Figure 22.3 Fossils, Cuvier, and Catastrophism • 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

10. Paleontology, the study of fossils • Was largely developed by French scientist Georges Cuvier • Observed that upper strata were younger and lower strata were older • Noticed that new species would appear in an older strata and then disappear in a newer strata. • Cuvier opposed the idea of gradual evolutionary change • And instead advocated catastrophism, speculating that each boundary between strata represents a catastrophe (flood or drought).

11. Theories of Gradualism • Gradualism • Is the idea that profound change can take place through the cumulative effect of slow but continuous processes. • 1795, James Hutton proposed that Earth’s geologic features could be explained by gradual mechanisms currently operating (ex. valleys are created by rivers)

12. Geologists Hutton and Charles Lyell • Perceived that changes in Earth’s surface can result from slow continuous actions still operating today • Lyell proposed uniformitarianism – same geologic processes are operating today as in the past and at the same rate. • Exerted a strong influence on Darwin’s thinking Charles Lyell, 1797-1875

13. One of the First “Ideas” of Evolution • Lamarck compared species today with the fossil record. • 1809, hypothesized that species evolve through use and disuse and the inheritance of acquired traits. • Organisms have an innate drive to become more complex. • But the mechanisms he proposed are unsupported by evidence Jean-Baptiste de Lamarck, 1744 - 1829

14. Lamarck’s View of Evolution • Plants and animals changed over time through the use and disuse of certain characteristics. • These acquired characteristics were inherited by the next generation. • No support for this notion.

15. Darwin and the HMS Beagle • During his travels • Darwin observed and collected many specimens of South American plants and animals • Darwin observed various adaptations of plants and animals • That inhabited many diverse environments Charles Darwin, 1831, age 22, starting his voyage on the HMS Beagle

16. Fig. 22.5 The Voyage of the HMS Beagle

17. Name Two (2) Observations that Darwin Made Leading to His Theory.Name One (1) Observation We’ve Since Made About the Natural World.

18. Darwin’s Observations about Evolution • 1. Fossil Record: noticed that the fossils of South America resembled living species of that continent. • Example: Glyptodon related to modernarmadillo?

19. Glyptodon Modern Armadillo, Omaha Zoo, 2009

20. Darwin’s Observations of Evolution • 2. Biogeography – plants and animals in temperate regions of South America resemble tropical species in South America than the temperate species in Europe. • The distribution of life across similar climates is not always the same; (climate alone is not causing diversity). • Closely related species are found in same geographic region.

21. NORTH AMERICA Sugar glider AUSTRALIA Flying squirrel Figure 22.17 • Different geographic regions, different mammalian “brands” • Have evolved independently from different ancestors Marsupial Mammal Placental Mammal

22. Charles Darwin, 1835, Galapagos

23. What’s so special about a bunch of islands?National Geographic SeriesGalapagos, Tape #254

25. Darwin’s Finches

26. The Galapagos Archipelago

27. Bartoloma Island

28. Isabela Island

29. Large ground finch Large tree finch Smallground finch Large cactus ground finch Camarhynchuspsitacula Greenwarbler finch Graywarbler finch Geospiza magnirostris Geospizafuliginosa Mediumtree finch Sharp-beaked ground finch Woodpecker finch Mediumground finch Geospiza conirostris Certhideaolivacea Certhideafusca Geospiza difficilis Camarhynchuspauper Cactusground finch Cactospizapallida Mangrovefinch Geospiza fortis Small tree finch Geospizascandens Camarhynchusparvulus Cactospiza heliobates Vegetarianfinch Cactus flowereater Seed eater Seed eater Platyspizacrassirostris Insect eaters Bud eater Ground finches Tree finches Warbler finches Common ancestor fromSouth American mainland Figure 1.23 • Darwin proposed that natural selection • Could enable an ancestral species to “split” into two or more descendant species, resulting in a “tree of life”

30. Large ground finch Large tree finch Smallground finch Large cactus ground finch Camarhynchuspsitacula Geospiza magnirostris Greenwarbler finch Graywarbler finch Geospizafuliginosa Mediumtree finch Sharp-beaked ground finch Woodpecker finch Geospiza conirostris Mediumground finch Certhideaolivacea Certhideafusca Geospiza difficilis Camarhynchuspauper Cactusground finch Cactospizapallida Mangrovefinch Geospiza fortis Small tree finch Geospizascandens Camarhynchusparvulus Cactospiza heliobates Vegetarianfinch Seed eater Seed eater Cactus flowereater Platyspizacrassirostris Insect eaters Bud eater Ground finches Tree finches Warbler finches Common ancestor fromSouth American mainland Figure 1.23

31. Seen one tortoise, you’ve seen them all? Dome-shaped Carapace Saddle-shaped Carapace

32. Galapagos Tortoise Distribution Galapagos tortoise distribution, Galapagos Islands. Redrawn from Iverson (1992).

33. Galapagos Tortoise-Env. Club 2008, Omaha Zoo

34. Darwin’s Focus on Adaptation • Years later, Darwin reassessed all that he had observed during the voyage of the Beagle • He began to perceive adaptation to the environment and the origin of new species as closely related processes Fig. 22.6

35. Alfred Russel Wallace, 1823-1913 • Explored Indonesia and southeast Asia, from 1854-1861, • Observed Tigers, Orangs, and Rhinos, Oh My!

36. Indian Rhino Sumatran Rhino Javan Rhino

39. Other Observations about Evolution • 3. Artificial Selection - humans have modified other species over many generations by selecting and breeding individuals that possess desired traits Fig. 22.10

40. Figure 1.19 • The Origin of Species articulated two main points… • Descent with modification • Natural selection

41. Population of organisms Overproduction and struggle for existence Hereditary variations Differences in reproductive success Evolution of adaptations in the population Figure 1.20 Natural Selection • Darwin proposed natural selection • As the mechanism for evolutionary adaptation of populations to their environments

42. 1 Populations with varied inherited traits 2 Elimination of individuals with certain traits. 3 Reproduction of survivors. 4 Increasing frequency of traits that enhance survival and reproductive success. Figure 1.21 • Natural selection is the evolutionary process that occurs… • When a population’s heritable variations are exposed to environmental factors that favor the reproductive success of some individuals over others.

43. The Origin of Species • Darwin developed two main ideas • Evolution explains life’s unity and diversity • Natural selection is a cause of adaptive evolution • The phrase descent with modification • Summarized Darwin’s perception of the unity of life • States that all organisms are related through descent from an ancestor that lived in the remote past

44. Elephant Phylogeny Fig. 22.7

45. Summary of Natural Selection • Natural selection is differential success in reproduction • That results from the interaction between individuals that vary in heritable traits and their environment • If an environment changes over time • Natural selection may result in adaptation to these new conditions

46. Over time natural selection can produce an increase • In the adaptation of organisms to their environment Fig. 22.11

47. Concept 22.3: Darwin’s theory explains a wide range of observations • Darwin’s theory of evolution • Continues to be tested by how effectively it can account for additional observations and experimental outcomes • Natural Selection in Action – Evolution continues today! • Guppies • HIV • Humans

48. Reznick and Endler transplanted guppies from pike-cichlid pools to killifish pools and measured the average age and size of guppies at maturity over an 11-year period (30 to 60 generations). EXPERIMENT Pools with killifish, but not guppies prior to transplant Experimental transplant of guppies Predator: Killifish; preys mainly on small guppies Guppies: Larger at sexual maturity than those in “pike-cichlid pools” Predator: Pike-cichlid; preys mainly on large guppies Guppies: Smaller at sexual maturity than those in “killifish pools” Figure 22.12 Differential Predation in Guppy Populations • Researchers have observed natural selection • Leading to adaptive evolution in guppy populations

49. RESULTS After 11 years, the average size and age at maturity of guppies in the transplanted populations increased compared to those of guppies in control populations. Control Population: Guppies from pools with pike-cichlids as predators 185.6 92.3 85.7 161.5 Weight of guppies at maturity (mg) Age of guppies at maturity (days) 58.2 48.5 76.1 67.5 Experimental Population: Guppies transplanted to pools with killifish as predators Males Females Males Females CONCLUSION Reznick and Endler concluded that the change in predator resulted in different variations in the population (larger size and faster maturation) being favored. Over a relatively short time, this altered selection pressure resulted in an observable evolutionary change in the experimental population.

50. The Evolution of Drug-Resistant HIV • In humans, the use of drugs • Selects for pathogens that through chance mutations are resistant to the drugs’ effects • Natural selection is a cause of adaptive evolution