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Darwinian View of Life: Evolution, Adaptations, and Natural Selection

Explore the scientific ideas of Charles Darwin, Lamarck's theory of evolution, the role of adaptations and variations, and the evidence for evolution. Understand the key concepts of natural selection and the genetic composition of populations.

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Darwinian View of Life: Evolution, Adaptations, and Natural Selection

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  1. Ch. 22 Warm-Up • What do you remember about Charles Darwin and his scientific ideas? • According to Campbell, what is the definition of “evolution”?

  2. Chapter 22 Descent with Modification: A Darwinian View of Life Part A: Darwin & Natural Selection

  3. What you must know: • How Lamarck’s view of the mechanism of evolution differed from Darwin’s. • The role of adaptations, variation, time, reproductive success, and heritability in evolution.

  4. Descent with Modification Theme: • Evolutionary change is based on the interactions between populations & their environment which results in adaptations (inherited characteristics) to increase fitness Evolution = change over time in the genetic composition of a population

  5. Linnaeus: founder of taxonomy; binomial nomenclature • Domain – Kingdom – Phylum – Class – Order – Family - Genus – Species • (Dear King Philip Came Over For Good Spaghetti) • Domains = Bacteria, Archaea, Eukarya • Classification based on anatomy & morphology Carolus Linnaeus1707-1778

  6. Hutton / Lyell: Gradualism= geologic change results from slow & gradual, continuous process Uniformitarianism= Earth’s processes same rate in past & present  therefore Earth is very old • Slow & subtle changes in organisms  big change James Hutton1726-1797 Charles Lyell1797-1875

  7. Jean-Baptiste Lamarck1744-1829 Lamarck: • Published theory of evolution (1809) • Use and Disuse: parts of body used  bigger, stronger (eg. giraffe’s neck) • Inheritance of Acquired Characteristics: modifications can be passed on • Importance: Recognized that species evolve, although explanation was flawed

  8. Malthus: • More babies born than deaths • Consequences of overproducing within environment = war, famine, disease (limits of human pop.) • Struggle for existence Thomas Malthus (1766-1834)

  9. Charles Darwin (1809-1882) • English naturalist • 1831: joined the HMS Beagle for a 5-year research voyage around the world • Collected and studied plant and animal specimens, bones, fossils • Notable stop: Galapagos Islands

  10. HMS Beagle (1831-1836)

  11. Galapagos Islands

  12. Darwin’s Finch Collection The birds were all about the same size, but the shape and size of the beaks of each species were different.

  13. GiantTortoise The vice-governor of the Galapagos Islands told Darwin that he could tell which island a particular tortoise came from by looking at its shell.

  14. Darwin waited 30 years before he published his ideas on evolution • Alfred Russell Wallace – published paper on natural selection first (1858) • Charles Darwin (1859): On the Origin of Species by Means of Natural Selection • Mechanism for evolution is Natural Selection • Darwin didn’t use “evolution”, but rather “descent with modification”

  15. “On the Origin of Species by Means of Natural Selection”By Charles Darwin(1859)

  16. Adaptations enhance an organism’s ability to survive and reproduce • Eg. Desert fox - large ears, arctic fox - small ears • Overproductionof offspring leads to competitionfor resources

  17. Therefore, if humans can create substantial change over short time, nature can over long time.

  18. Key Ideas of Natural Selection: • Competition for limited resources results in differential survival. • Evolutionary Fitness: Individuals with more favorable phenotypes more likely to survive and produce more offspring, and pass traits to future generations • If environment changes or individuals move to new environment, new adaptations and new species may arise. • Populationsevolve, not individuals.

  19. PBS: What Darwin Never Knew Video Clip: 20:18 – 31:27

  20. Ch. 22 Warm-Up • Compare and contrast natural selection vs. artificial selection. • What are the key ideas of natural selection? • Define and give an example for the following: • Homologous structure • Vestigial structure • Analogous structure

  21. Chapter 22 Descent with Modification: A Darwinian View of Life Part B: Evidence for Evolution

  22. Recap main ideas of natural selection: • Evolution is change in species over time. • There is overproduction of offspring, which leads to competition for resources. • Heritable variations exist within a population. • These variations can result in differential reproductive success. • Over generations, this can result in changes in the genetic composition of the population. Remember: Individuals do NOT evolve! Populations evolve.

  23. Evidence for Evolution: • Direct Observations • Fossil Record • Homology • Biogeography

  24. Evidence for Evolution

  25. Evidence for Evolution:1. Direct Observations Examples: • Insect populations become resistant to pesticides (DDT) • Antibiotic-resistant bacteria (MRSA) • Peppered moth (pollution in city vs. country)

  26. The Rise of MRSA(methicillin-resistant Staphylococcus aureus)

  27. Evidence for Evolution:2. Fossil Record • Fossils = remains or traces of organisms from past • Found in sedimentary rock • Paleontology: study of fossils • Show evolutionary changes that occur over time and origin of major new groups of organisms Ankle bones

  28. Prokaryotes (oldest fossils)  eukaryotes (fish – amphibians – reptiles – birds – mammals) • Transitional forms = links to modern species

  29. Evidence for Evolution:3. Homology • Homology: characteristics in related species can have underlying similarity even though functions may differ • Examples: • Homologous structures: similar anatomy from common ancestors (eg. forelimbs of human/cat/whale/bat) • Embryonic homologies: similar early development (eg. vertebrate embryos with tail & pharyngeal pouches) • Vestigial organs: structures w/little or no use (eg. flightless bird wings) • Molecular homologies: similar DNA and amino acid sequences

  30. Homologous Structures

  31. Embryonic Development

  32. Vestigial Structures

  33. Molecular Homologies • Compare DNA and amino acid sequences

  34. Evolutionary Tree

  35. Convergent Evolution • Distantly related species can resemble one another • Similar problem, similar solutions! • Analogous structures: similar structures, function in similar environments • Eg. Torpedo shape of shark, penguin, & dolphin

  36. Evidence for Evolution:4. Biogeography • Biogeography = geographic distribution of a species • Species in nearby geographic areas resemble each other • Continental drift and Pangaea explains similarities on different continents • Endemic species: found at a certain geographic location and nowhere else • Eg. Marine iguanas in the Galapagos

  37. Island Biogeography

  38. Galapagos Tortoises

  39. Tree of Life

  40. HHMI Short Film:Natural Selection & Adaptation Rock Pocket Mice Running Time: 10:25 min

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