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Evolution

Evolution. Darwin’s Theory of Natural Selection. MAIN IDEA: Charles Darwin developed a theory of evolution based on natural selection. Why was Darwin’s work controversial?. Evolution vs. Creationism. Creationism – belief that God created all living things to be unique

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Evolution

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  1. Evolution

  2. Darwin’s Theory of Natural Selection MAIN IDEA: Charles Darwin developed a theory of evolution based on natural selection.

  3. Why was Darwin’s work controversial?

  4. Evolution vs. Creationism • Creationism – belief that God created all living things to be unique • Evolution – theory that organisms have changed over time.

  5. Until the 1800s • People thought the same types of organisms on earth were always in existence • This changed when scientists found fossils of organisms no longer on earth

  6. What made Darwin question previous assumptions on how different organisms came to be?

  7. Scientists observed… • Fossil evidence • Many different species • Variations (differences) within species

  8. Change in Thought • Scientists began to wonder how and why these changes took place • 2 biologists believed organisms changed in response to their environments: • French Jean Baptiste Lamarck • British Charles Darwin

  9. Lamarck’s Theory • 1809 – Lamarck proposed his theory of evolution • Theory based on 2 hypotheses: • Organisms develop traits by the use and disuse of body parts • Acquired characteristics – passed from parents to offspring

  10. According to Lamarck, why do giraffes have long necks?

  11. Lamarck’s giraffe example(Don’t Copy) • Lamarck assumed giraffes had short necks originally and ate grass • Grass died due to climate change • Giraffes ate leaves off trees • As giraffes stretched necks, necks grew • Giraffe’s acquired long necks – passed to future generations • Scientists questioned this theory…

  12. Charles Darwin • Born in 1809 • Age 22, went on voyage on HMS Beagle(British ship) as a naturalist • Mapping expedition of S. America and S. Pacific

  13. Darwin’s Thoughts (Don’t Copy) • Charles Lyell’s book influenced Darwin -Lyell said Earth was millions of years old • Observed fossils of marine animals on mountains, etc • Observed changing earth: earthquakes, volcanoes, etc; saw change in the land • Thought organisms would have to adapt to these changes

  14. Darwin’s Studies • Observed thousands of different species • Took careful notes • Collected specimens • Studies fossils

  15. Galapagos Islands (Don’t Copy) • Off coast of Ecuador • Observed MANY different species • Many similar to those on coast of S. America • Observed tortoises, iguanas, finches, etc with slight differences on different islands • Ex: different beaks of finches

  16. Help from Gould (Don’t Copy) • John Gould, another British naturalist • Concluded finches were different species, and were not on mainland of S. America • Darwin though species changed after reaching islands

  17. DO NOW • What is the difference between natural selection and artificial selection? • What is the difference between natural selection and evolution?

  18. Artificial vs. Natural Selection • Artificial - breeding for desired traits • Natural – naturally “desired” traits are bred more often – causes gradual change in species over time (evolution)

  19. Darwin’s Theory • Published book: On the Origin of Species by Means of Natural Selection with help from another scientist, Alfred Russel Wallace • Theory based on 4 main ideas: • Variations • Inheritance of traits • Overproduction • Survival of the fittest

  20. Variations • Variations (differences) occur among members of the same species • Ex: different breeds of dogs, horses, cats, etc. Inheritance of Variations • Traits are inherited

  21. Overproduction • Organisms produce more organisms than can survive and reproduce • This ensures that some offspring will survive to reproduce • Ex: fish, insects, frogs, etc.

  22. Survival of the Fittest • Organisms with traits that are better for adapting survive to reproduce • Pass on these useful traits • Natural selection – environment determines which variations will be selected

  23. Peppered Moth Example (DON’T COPY) • Early 1800s, England • Peppered moths were mostly light gray; few were white, few were black (variations) • Gray blended with tree trunks – birds didn’t see or eat them, so they survived, but black ones were eaten

  24. Peppered Moth Cont’d (DON’T COPY) • Industrial Revolution – many factories built • Black soot on trees • Which moths were NOW more likely to survive?

  25. Do Now • Once, many years ago, horses were the size of cats. Now, they are obviously much bigger. How would Lamarck explain this change? How would Darwin explain it?

  26. Evidence of Evolution • Fossils • Anatomy • Embryos • Molecules • Biogeography

  27. Fossil Evidence • Show extinct species • Show relationships between current and ancient organisms • Show intermediate species – those in between ancient and modern species • Difference in traits – derived vs. ancestral

  28. Anatomical Evidence • Similar structures found in closely related species; have common ancestor • Diverse vertebrates have similar limb structures, but may not have same function –homologous • Vestigial structures – structures not currently used by organism; evidence of an organism’s evolutionary past Ex: hind limbs of dolphins/whales

  29. Homologous Structures

  30. Homologous vs. Analogous • Remember, homologous – similar STRUCTURE • Analogous – structures with similar FUNCTIONS, but different structures/origins • Ex: bat’s wing and bird’s wing - analogous

  31. Evidence in Embryos • Pattern of meiosis (gametes)  fertilization  mitosis (adults) • All vertebrate embryos have homologous structures that may not be in adults: • Tails (most adults keep their tails!) • Limb buds – become limbs • Vertebrates have a common ancestor

  32. Molecular Evidence DNA: • Basic genetic code for each species • Ex: humans all have same basic genetic code • Species that are similar have many similarities in their DNA • Species with a more distant ancestor have more differences in DNA

  33. Molecular Evidence Proteins: • Because of similar DNA, organisms of the same species have the same basic proteins • Similar species – similar amino acid sequences in their proteins

  34. Biogeography • Study of distribution of organisms on earth • Similar environments lead to similar adaptations in organisms, even if far apart

  35. Adaptations • Traits that allow for survival • Fitness – way to measure how effective traits are • Examples of adaptations: • Camouflage • Mimicry

  36. Remember that… • Not all traits evolve slowly; Ex: bacteria • Not all traits increase fitness • Mutations can be a source of new traits

  37. Evolution and Genetics

  38. Population • Members of same species living in same area • All genes in a population = gene pool

  39. Population Genetics • Allele frequency – percent of certain alleles (gene types) in a population’s gene pool • Ex: all homozygous red flowers have a 100% frequency for red alleles • Usually remains stable in a population

  40. Changes in the Gene Pool • Changes can occur in the gene pool, which could cause evolution • Kinds or percentages of genes can change • 4 things cause these changes • Natural selection • Mutation • Migration • isolation

  41. 4 Factors Change the Gene Pool 1. Natural selection • Well-adapted organisms survive to reproduce • Pass on genes to next generation, increasing the gene frequency

  42. 4 Factors Change the Gene Pool 2. Mutation • Adds a new gene to the gene pool • Can cause small, immediate change, or go undetected for generations • Can be helpful, harmful, or neutral

  43. 4 Factors Change the Gene Pool 3. Migration • Movement of organisms into or out of a population • Causes gene flow – movement of genes in or out of populations

  44. 4 Factors Change the Gene Pool 4. Isolation • Organisms become separate from other organisms (geographic isolation) • Caused by physical barriers, natural disasters, etc • Causes speciation • Causes reproductive isolation between the now separate species

  45. Create • With your group, pick any species, and create a scenario as to how it may evolve based on your assigned factor. Base your predictions on facts about the species. Describe and/or draw your predictions, and then present to the class!

  46. The Rate of Evolution

  47. Gradualism • Evolution through slow change • Believed to be true by Darwin and many other scientists • Fossil evidence supports this

  48. Punctuated Equilibrium • Species remain unchanged for thousands of years, then suddenly undergo rapid changes • Fossil evidence of trilobites – unchanged for millions of years, then suddenly died off

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