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Chapter 15

Chapter 15. Darwin’s Theory of Evolution 15.1 Life’s diversity. 0. North America. Great Britain. Europe. Asia. ATLANTIC OCEAN. PACIFIC OCEAN. Africa. PACIFIC OCEAN. Equator. The Galápagos Islands. PACIFIC OCEAN. South America. Pinta. Genovesa. Australia. Marchena. Equator.

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Chapter 15

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  1. Chapter 15 Darwin’s Theory of Evolution 15.1 Life’s diversity 0 NorthAmerica GreatBritain Europe Asia ATLANTICOCEAN PACIFICOCEAN Africa PACIFICOCEAN Equator TheGalápagosIslands PACIFICOCEAN SouthAmerica Pinta Genovesa Australia Marchena Equator Andes Cape ofGood Hope Santiago DaphneIslands Pinzón Fernandina Tasmania NewZealand Cape Horn Isabela SantaCruz SantaFe SanCristobal Tierra del Fuego 40 km 0 Florenza Española 40 miles 0 0

  2. How does a population evolve? What are the conditions for a non-evolving population? What a population looks like after evolution and natural selection? After a population evolves, then what happens? Speciation Definition of species How speciation occurs? Macroevolution: Large-scale evolution occurring over geologic time that results in the formation of new taxonomic groups.

  3. 15.2 DARWIN’S THEORY OF EVOLUTION Darwin’s experiences during the voyage of the Beagle helped him frame his ideas on evolution While on the voyage of the HMS Beagle in the 1830s, Charles Darwin observed similarities between living and fossil organisms and the diversity of life on the Galápagos Islands In the century prior to Darwin, the study of fossils suggested that life forms change Geologists proposed that a very old Earth is changed by gradual processes 0 • Darwin’s ideas can be traced back to the ancient Greeks • Western philosophy dates back to Plato (427-347 B.C.) and Aristotle (384-322 B.C.), and Genesis, which accepts that God created everything in its present form over the course of six day.

  4. Darwin had personal knowledge of and interest in artificial selection and found convincing evidence for his ideas in the results of artificial selection The selective breeding of domesticated plants and animals 15-3 Darwin proposed natural selection as the mechanism of evolution • Darwin observed that organisms • -- Produce more offspring than the environment can support • -- that the expression of traits varies among the individuals of a population, and that many of these traits are heritable Hundreds to thousandsof years of breeding(artificial selection) Ancestral dog (wolf) Figure 13.2B Figure 13.2A 0

  5. Two important points can be drawn from Darwin’s theory of natural selection: Ancestral species gave rise to the diverse life forms by transfer of heritable traits to offspring that best promote reproduction. He called this “descent with modification.” Over vast amounts of time, the gradual accumulation of changes in the characteristics among the individuals in a population occurs. African wild dog Coyote Jackal Wolf Fox Thousands tomillions of yearsof natural selection Ancestral canine Figure 13.2C 0

  6. 15.3 The study of fossils provides strong evidence for evolution The fossil record reveals that organisms have evolved in a historical sequence H. The fossil record is an array of fossils appearing within the layers (strata) of sedimentary rocks. Sedimentary rocks form from accumulations of waterborne sediments. Sedimentary deposits occur in strata. Each layer contains fossils of organisms among the deposits, with younger strata on top of older strata. 0 Preserved bones Plants and reptile fossils Marine fossils Primitive fish bones Shell fossils

  7. Many fossils link early extinct species with species living today The fossil record shows a historical sequence of organisms from the oldest known fossils, prokaryotes, dating from more than 3.5 billion years ago, through the subsequent appearance of eukaryotes, on through many intermediate steps to modern forms—a sequence that has an overall pattern of change from simple to more complex forms. Figure 13.3I 0

  8. Biogeography makes observations about the distribution of different but obviously related life forms around the world and in neighboring geographical regions. The geographic distribution of species suggested to Darwin that organisms evolve from common ancestors Darwin noted that Galápagos animals (e.g., finches) resembled species of the closest South American mainland more than animals on ecologically similar but distant islands A mass of other evidence reinforces the evolutionary view of life 0 Comparative Anatomy: the comparison of body structures in different species • Homology is the similarity in characteristics that result from common ancestry. • Homologous structures are features that often have different functions but are structurally similar because of common ancestry

  9. 0 Pharyngealpouches Post-analtail Human embryo Chick embryo Figure 13.4B Comparative Embryology The comparison of early stages of development among different organisms -- shows that different organisms go through similar embryonic stages. For example, all vertebrates gill pouches appear in the throat region. In addition to all vertebrates have in common the presence of, at some point in their life cycle, a notochord (a cartilaginous supporting rod), a dorsal hollow nerve cord (spinal cord), and a post-anal tail.

  10. Molecular Biology -- demonstrates the universality of the genetic code, the conservation of amino acid sequences in proteins such as hemoglobin, and the presence of very similar homeotic genes in very different species. Table 13.4 0 Darwin’s most daring hypothesis, that all living organisms are related, is supported by the findings from molecular biology studies.

  11. Evidence and complications in the study of Evolution:Homologous Structures Flying Swimming Running Grasping

  12. Analogous structures: An organ or structure that is similar in function to one in another kind of organism but is of dissimilar evolutionary origin. 0 Vestigal organs is another line of evidence of common ancestry

  13. A review: Homologous vs. Analogous Structures Not homologous;analogous Not homologous;not analogous Homologous;not analogous Homologous;analogous

  14. Populations are the units of evolution A population: Is a group of individuals of the same species living in the same place at the same time A species is a group of populations whose individuals can interbreed and produce fertile offspring Population genetics: Studies how populations change genetically over time The modern synthesis: Connects Darwin’s theory with population genetics A gene pool : Is the total collection of genes in a population at any one time Microevolution: Is a change in the relative frequencies of alleles in a gene pool POPULATION GENETICS AND THE MODERN SYNTHESIS 0

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