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Evolution

Discover the groundbreaking work of Charles Darwin and how his theory of evolution based on natural selection revolutionized scientific thought in the 19th century. Explore the controversies, contrasting Evolution versus Creationism, Lamarck's theory, Darwin's studies, and the evidence supporting evolution.

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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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