Chapter22

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Chapter22

  1. 1. Chapter 22Descent with Modification: ADarwinian View of LifePowerPoint Lectures forBiology, Seventh Edition Neil Campbell and Jane ReeceLectures by Chris RomeroCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  2. 2. • 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 SelectionCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  3. 3. • The Origin of Species – Focused biologists’ attention on the great diversity of organisms Figure 22.1Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  4. 4. • Darwin made two major points in his book – He presented evidence that the many species of organisms presently inhabiting the Earth are descendants of ancestral species – He proposed a mechanism for the evolutionary process, natural selectionCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  5. 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 lifeCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  6. 6. • The historical context of Darwin’s life and ideas Linnaeus (classification) Hutton (gradual geologic change) Lamarck (species can change) Malthus (population limits) Cuvier (fossils, extinction) Lyell (modern geology) Darwin (evolution, nutural selection) Mendel (inheritance) Wallace (evolution, natural selection) American Revolution French Revolution U.S. Civil War 1750 1800 1850 1900 1795 Hutton proposes his theory of gradualism. 1798 Malthus publishes “Essay on the Principle of Population.” 1809 Lamarck publishes his theory of evolution. 1830 Lyell publishes Principles of Geology. 1831–1836 Darwin travels around the world on HMS Beagle. 1837 Darwin begins his notebooks on the origin of species. 1844 Darwin writes his essay on the origin of species. 1858 Wallace sends his theory to Darwin. 1859 The Origin of Species is published. 1865 Mendel publishes inheritance papers. Figure 22.2Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  7. 7. Resistance to the Idea of Evolution • The Origin of Species – Shook the deepest roots of Western culture – Challenged a worldview that had been prevalent for centuriesCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  8. 8. 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 perfectCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  9. 9. • 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”Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  10. 10. 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 Figure 22.3Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  11. 11. • Paleontology, the study of fossils – Was largely developed by French scientist Georges Cuvier • Cuvier opposed the idea of gradual evolutionary change – And instead advocated catastrophism, speculating that each boundary between strata represents a catastropheCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  12. 12. Theories of Gradualism • Gradualism – Is the idea that profound change can take place through the cumulative effect of slow but continuous processesCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  13. 13. • Geologists Hutton and Lyell – Perceived that changes in Earth’s surface can result from slow continuous actions still operating today – Exerted a strong influence on Darwin’s thinkingCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  14. 14. Lamarck’s Theory of Evolution • Lamarck hypothesized that species evolve – Through use and disuse and the inheritance of acquired traits – But the mechanisms he proposed are unsupported by evidence Figure 22.4Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  15. 15. • Concept 22.2: In The Origin of Species, Darwin proposed that species change through natural selection • As the 19th century dawned – It was generally believed that species had remained unchanged since their creation, but a major change would challenge this thinkingCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  16. 16. Darwin’s Research • As a boy and into adulthood, Charles Darwin – Had a consuming interest in nature • Soon after Darwin received his B.A. degree – He was accepted on board the HMS Beagle, which was about to embark on a voyage around the worldCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  17. 17. The Voyage of the Beagle • During his travels on the Beagle – Darwin observed and collected many specimens of South American plants and animals • Darwin observed various adaptations of plants and animals – That inhabited many diverse environmentsCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  18. 18. • Darwin’s interest in the geographic distribution of species – Was kindled by the Beagle’s stop at the Galápagos Islands near the equator west of South America England EUROPE NORTH AMERICA PACIFIC ATLANTIC OCEAN OCEAN Galápagos AFRICA HMS Beagle in port Islands SOUTH Darwin in 1840, AMERICA after his return AUSTRALIA Andes Cape of Good Hope Tasmania Cape Horn New Tierra del Fuego Zealand Figure 22.5Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  19. 19. Darwin’s Focus on Adaptation • As 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 processesCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  20. 20. • From studies made years after Darwin’s voyage – Biologists have concluded that this is indeed what happened to the Galápagos finches (a) Cactus eater. The long, (c) Seed eater. The large ground sharp beak of the cactus finch (Geospiza magnirostris) ground finch (Geospiza has a large beak adapted for scandens) helps it tear cracking seeds that fall from and eat cactus flowers plants to the ground. and pulp. Figure 22.6a–c (b) Insect eater. The green warbler finch (Certhidea olivacea) uses its narrow, pointed beak to grasp insects.Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  21. 21. • In 1844, Darwin wrote a long essay on the origin of species and natural selection – But he was reluctant to introduce his theory publicly, anticipating the uproar it would cause • 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 yearCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  22. 22. The Origin of Species • Darwin developed two main ideas – Evolution explains life’s unity and diversity – Natural selection is a cause of adaptive evolutionCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  23. 23. Descent with Modification • 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 pastCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  24. 24. • In the Darwinian view, the history of life is like a tree – With multiple branchings from a common trunk to the tips of the youngest twigs that represent the diversity of living organisms Sirenia Elephas Loxodonta Loxodonta Hyracoidea (Manatees maximus africana cyclotis Years ago (Hyraxes) and relatives) (Africa) (Asia) (Africa) Mammuthus Stegodon Mammut Deinotherium Platybelodon Millions of years ago Barytherium Moeritherium Figure 22.7Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  25. 25. Natural Selection and Adaptation • Evolutionary biologist Ernst Mayr – Has dissected the logic of Darwin’s theory into three inferences based on five observationsCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  26. 26. • Observation #1: For any species, population sizes would increase exponentially – If all individuals that are born reproduced successfully Figure 22.8Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  27. 27. • Observation #2: Nonetheless, populations tend to be stable in size – Except for seasonal fluctuations • Observation #3: Resources are limited • Inference #1: Production of more individuals than the environment can support – Leads to a struggle for existence among individuals of a population, with only a fraction of their offspring survivingCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  28. 28. • Observation #4: Members of a population vary extensively in their characteristics – No two individuals are exactly alike Figure 22.9Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  29. 29. • Observation #5: Much of this variation is heritable • Inference #2: Survival depends in part on inherited traits – Individuals whose inherited traits give them a high probability of surviving and reproducing are likely to leave more offspring than other individualsCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  30. 30. • Inference #3: This unequal ability of individuals to survive and reproduce – Will lead to a gradual change in a population, with favorable characteristics accumulating over generationsCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  31. 31. Artificial Selection • In the process of artificial selection – Humans have modified other species over many generations by selecting and breeding individuals that possess desired traits Terminal Lateral bud buds Cabbage Brussels sprouts Flower Leaves cluster Cauliflower Kale Flower Stem and stems Broccoli Wild mustard Kohlrabi Figure 22.10Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  32. 32. 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 environmentCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  33. 33. • Natural selection can produce an increase over time – In the adaptation of organisms to their environment (a) A flower mantid in Malaysia (b) A stick mantid in Africa Figure 22.11Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  34. 34. • If an environment changes over time – Natural selection may result in adaptation to these new conditionsCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  35. 35. • 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 outcomesCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  36. 36. Natural Selection in Action • Two examples – Provide evidence for natural selectionCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  37. 37. Differential Predation in Guppy Populations • Researchers have observed natural selection – Leading to adaptive evolution in guppy populations EXPERIMENT 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). Pools with killifish, but not guppies prior to transplant Experimental transplant of Predator: Killifish; preys guppies 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 22.12Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  38. 38. 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. Weight of guppies at maturity (mg) at maturity (days) Control Population: Guppies Age of guppies 185.6 161.5 85.7 92.3 from pools with pike-cichlids 58.2 as predators 48.5 67.5 76.1 Experimental Population: Guppies transplanted to Males Females Males Females pools with killifish as predators 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.Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  39. 39. 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 evolutionCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  40. 40. • Researchers have developed numerous drugs to combat HIV – But using these medications selects for viruses resistant to the drugs Patient Percent of HIV resistant to 3TC No. 1 Patient No. 2 Patient No. 3 Weeks Figure 22.13Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  41. 41. • The ability of bacteria and viruses to evolve rapidly – Poses a challenge to our societyCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  42. 42. Homology, Biogeography, and the Fossil Record • Evolutionary theory – Provides a cohesive explanation for many kinds of observationsCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  43. 43. Homology • Homology – Is similarity resulting from common ancestryCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  44. 44. Anatomical Homologies • Homologous structures between organisms – Are anatomical resemblances that represent variations on a structural theme that was present in a common ancestor Human Cat Whale Bat Figure 22.14Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  45. 45. • Comparative embryology – Reveals additional anatomical homologies not visible in adult organisms Pharyngeal pouches Post-anal tail Chick embryo Human embryo Figure 22.15Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  46. 46. • Vestigial organs – Are some of the most intriguing homologous structures – Are remnants of structures that served important functions in the organism’s ancestorsCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  47. 47. Molecular Homologies • Biologists also observe homologies among organisms at the molecular level – Such as genes that are shared among organisms inherited from a common ancestorCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  48. 48. Homologies and the Tree of Life • The Darwinian concept of an evolutionary tree of life – Can explain the homologies that researchers have observedCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  49. 49. • Anatomical resemblances among species – Are generally reflected in their molecules, their genes, and their gene products Percent of Amino Acids That Are Identical to the Amino Acids in a Species Human Hemoglobin Polypeptide Human 100% Rhesus monkey 95% Mouse 87% Chicken 69% Frog 54% 14% Figure 22.16 LampreyCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  50. 50. Biogeography • Darwin’s observations of the geographic distribution of species, biogeography – Formed an important part of his theory of evolutionCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  51. 51. • Some similar mammals that have adapted to similar environments – Have evolved independently from different ancestors NORTH AMERICA Sugar glider AUSTRALIA Flying squirrel Figure 22.17Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  52. 52. The Fossil Record • The succession of forms observed in the fossil record – Is consistent with other inferences about the major branches of descent in the tree of lifeCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  53. 53. • The Darwinian view of life – Predicts that evolutionary transitions should leave signs in the fossil record • Paleontologists – Have discovered fossils of many such transitional forms Figure 22.18Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  54. 54. What Is Theoretical about the Darwinian View of Life? • In science, a theory – Accounts for many observations and data and attempts to explain and integrate a great variety of phenomenaCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
  55. 55. • Darwin’s theory of evolution by natural selection – Integrates diverse areas of biological study and stimulates many new research questionsCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

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