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Evolution

Evolution. Social Theory. Thomas Malthus (1798) Describes role of competition for limited resources in human societies. Not everyone will compete successfully. Historical Viewpoints. Historically, Earth and all organisms have always existed in current state. Creation by higher authority

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Evolution

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  1. Evolution

  2. Social Theory Thomas Malthus (1798) • Describes role of competition for limited resources in human societies. • Not everyone will compete successfully.

  3. Historical Viewpoints • Historically, Earth and all organisms have always existed in current state. • Creation by higher authority • 18th-19th centuries, scientists began to realize that things may be much different than originally thought.

  4. Darwin and Evolution • Who was Charles Darwin? • English scientist born in 1809 • Gave up medical studies, went to seminary. • Performed 30 years of observation on various species • Wrote “On the Origin of Species by Means of Natural Selection, or the Preservation of Favored Races in the Struggle for Life”

  5. Darwin and Evolution • Who was Charles Darwin? • Theory of Evolution: One type of organism can gradually evolve into another. • Proposed natural selection as the mechanism of evolution that produced the diversity of life on Earth.

  6. Evidence Used by Darwin • Fossils (armadillo) • Geographical distribution • Oceanic island observations

  7. Evidence Used by Darwin • Fossils: • Extinct species resemble current species. • Rock strata studies: Progressive changes in characteristics can be seen in fossils found in varying layers.

  8. Evidence Used by Darwin • Geographical Distribution: • Lands with similar climates have unrelated plant and animal life. • Diversity is not entirely influenced by climate and the environment.

  9. Evolutionary Thinking Before Darwin • Jean-Baptiste de Lamarck: Evolution (1809) • French naturalist • Organisms changed forms over generations through the inheritance of acquired characteristics • He believed that, over time, an animal would acquire enough changes that one species would diverge into two • Falsifiable: Animals don’t pass traits in accordance to behavior…how?

  10. Evolutionary Thinking Before Darwin • Charles Lyell: Geologist • “Principles of Geology” (1830) • Geological forces still operating could account for the changes geologists could see in the Earth’s surface. • Earth had not been placed into final form at the moment of creation, but was undergoing steady change. • If it is possible for the Earth to evolve, why not the living organisms?

  11. Evolutionary Thinking Before Darwin • LaMarck: • Got this idea correct: • Organisms can evolve…one kind of organism can be ancestral to a different kind of organism.

  12. Evolutionary Thinking Before Darwin • Georges Cuvier: Extinction • French scientist • Examined fossils in rock formations and found conclusive evidence of the extinction of species.

  13. Evolutionary Thinking Before Darwin • Alfred Russell Wallace: Natural selection • English naturalist • Two years after Darwin had began his work…half a world away. • Collected bird and butterfly specimens from South America and Southeast Asia • Natural selection was the force that shapes evolution.

  14. Natural Processes Underlying Evolution • Genetic variation among members of a population. • Inheritance of variations by offspring • Natural selection

  15. What is Natural Selection? • Organisms that possess superior physical, behavioral, or other attributes are more likely to survive than those that do not possess them. • Survival allows the favorable attributes to be passed on to offspring. • As the frequency of these attributes increases in a population, the population as a whole gradually changes (Survival of the fittest)

  16. Evidence for Evolution • Radiometric dating; • Fossil placement; • Comparative morphology and embryology: • Homologous structures owing to inheritance from a common ancestor (forelimb structure in a diverse group of mammals, bats, whales, cats, gorilla…one large upper bone, joined to two intermediate bones, joined to five digits.)

  17. Natural Selection: differential success in reproduction; only form of microevolution that adapts a population to its environment

  18. Evidence for Evolution • Evidence from Molecular Biology • DNA (nucleotide bases) • Experimental Evidence • Brighter male guppies attracted more females than drab guppies, but they also attracted more predators. • Removed predators and bright colored male guppy population grew…reintroduced predators and drab colored male guppy population increased.

  19. Darwin and Natural Selection • Force that causes populations to evolve. • Relies on variation in traits in any population • Based on 3 main principles 1) Competition 2) Survival of the Fittest 3) Descent with Modification

  20. 1. Competition • Members of a species population are in competition with each other for resources like food and space. • “Struggle for existence” • Those individuals with traits that give them an advantage make them better competitors.

  21. 2. Survival of the Fittest • Organism’s ability to survive in it’s environment called it’s fitness • Greater fitness means more reproductive success! • Random variation in traits in a population • If trait a greater fitness, call it an adaptation • Some harmful, a less fitness

  22. 3. Descent with Modification • Alleles for adaptations are passed on through generations and accumulate in a species’ gene pool over time. • If enough difference, produces a newspecies. • Ex. Hawaiian Honeycreepers • All Hawaiian honeycreepers have similarities in skeletal and muscle structure that indicate they are closely related.

  23. Each of the Hawaiian honeycreeper species has a bill specialized for eating certain foods. Scientists suggest that all 23 honeycreeper species apparently arose from a single species that migrated to Hawaii.

  24. On the Origin of Species • Published 1859 • Summarized his ideas on causes of speciation • Darwin's On the Origin of Species by Means of Natural Selection, made several points that had major impact on nineteenth-century thought:

  25. Hutton and Lyell (geologists) • James Hutton (1785) - examined geologic features such as rock layers and erosion, concluded earth very old. • Charles Lyell (1833) through observing current earth processes, believed that these same geologic processes shaped the earth as we currently see it.

  26. Early Evolutionist • Jean-Baptiste Lamarck (1809) • Recognized that species change over time • Idea: Inheritance of Acquired Traits

  27. Evolution: Getting from There to Here • According to Lamarck, individuals passed on to offspring body and behavior changes acquired during their lives • for example, giraffes evolved long necks because ancestral giraffes tended to stretch their necks and this neck extension was passed on to subsequent generations

  28. Figure 17.1(a) How did long necks evolve in giraffes?

  29. 17.1 Evolution: Getting from There to Here • According to Darwin, the variation is not created by experience but already exists when selection acts on it • populations of ancestral giraffes contained variation in neck length • individuals who were able to feed higher up on the trees had more food and so were able to survive and reproduce better than their shorter-necked relatives

  30. Figure 17.1 (b) How did long necks evolve in giraffes?

  31. 17.1 Evolution: Getting from There to Here • There are two views concerning the rate of evolutionary change • gradualism states that evolutionary change occurs extremely slowly • such change would be nearly imperceptible from generation to generation, but would accumulate over the course of millions of years • punctuated equilibrium states that species experience long periods of little or no evolutionary change (termed stasis), interrupted by bursts of evolutionary change

  32. Figure 17.2 Two views of the pace of macroevolution

  33. 17.2 The Evidence for Evolution • There are many lines of evidence supporting Darwin’s theory of evolution • the fossil record comprises the most direct evidence of macroevolution • fossils are the preserved remains, tracks, or traces of once-living organisms • they are created when organisms or their traces become buried in sediment • by dating the rocks in which the fossils occur, one can get an accurate idea of how old the fossils are

  34. 17.2 The Evidence for Evolution • Fossils in rock represent a history of evolutionary change • fossils are treated as samples of data and are dated independently of what the samples are like • successive changes through time are a data statement • thus, the statement that macroevolution has occurred is a factual observation

  35. Fossil Record • Preserved remain of ancient life in rock support change over time. • Fossils found in lower levels of rock older than ones above. (relative age) • Majority of species that have existed on this planet are extinct! • Very hard for an organism to become a fossil.

  36. When there are remains of organic material (carbon) in a fossil, we can use carbon dating to approximate age. • Radioactive isotopes decay at a constant rate • Half Life  length of time for ½ of an isotope to decay • Ex. Carbon-14 decays to Nitrogen-14 • Half-life = 5,730 years • Carbon 14 can only be uses to date fossils less than 50,000 years old!

  37. Figure 17.3 Testing the theory of evolution with fossil titanotheres

  38. 17.2 The Evidence for Evolution • The anatomical record also reflects evolutionary history • for example, all vertebrate embryos share a similar set of developmental instructions and features Figure 17.4 Embryos show our early evolutionary history

  39. Comparative Embryology • closely related organisms go through similar stages during their embryonic development

  40. 17.2 The Evidence for Evolution • Homologous structures are derived from the same body part present in an ancestor • for example, the same bones might be put to different uses in related species • Analogous structures are similar-looking structures in unrelated lineages • these are the result of parallel evolutionary adaptations to similar environments • this form of evolutionary change is referred to as convergent evolution

  41. Homologous versus Analogous Structures Figure 17.5 Homology among vertebrate limbs Figure 17.6 Convergent evolution: many paths to one goal

  42. Homologous Structures (Comparative Anatomy) • Scientists note similarities among physiology of organisms • Morphologically similar structures that perform different functions are called homologous structures.

  43. Analogous Structures • Serve similar function but have a much different structure • Ex. Insect wing and bird wing • Ex. Whale fin and fish fin

  44. 17.2 The Evidence for Evolution • Traces of our evolutionary past are also evident at the molecular level • organisms that are more distantly related should have accumulated a greater number of evolutionary differences than two species that are more closely related • the same pattern of divergence can be seen at the protein level

  45. Figure 17.7 Molecules reflect evolutionary divergence

  46. 17.2 The Evidence for Evolution • Evolutionary changes appear to accumulate at a constant rate • this permits changes in an individual gene, compared over a broad array of organisms, to be dated from the time of divergence • this dating is referred to as a molecular clock • for example, changes have accumulated in the cytochrome c gene at a constant rate

  47. Figure 17.8 The molecular clock of cytochrome c

  48. 17.3 Evolution’s Critics • The theory of evolution by natural selection is the subject of often-bitter public controversy • the controversy began soon after the publication of The Origin of Species but, by the turn of the twentieth century, evolution was generally accepted by the world’s scientific community • more recent criticism has come from the following sources • the Fundamentalist Movement • the Scientific Creationist Movement • Local Action • Intelligent Design

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