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Evolution

Evolution. A history of evolutionary thought :. Linneaus Swedish botanist Founder of taxonomy System of naming and classifying organisms Grouped things into categories that would later be used by Darwin to show relationships. George Cuvier

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Evolution

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  1. Evolution

  2. A history of evolutionary thought : • Linneaus • Swedish botanist • Founder of taxonomy • System of naming and classifying organisms • Grouped things into categories that would later be used by Darwin to show relationships

  3. George Cuvier • Founded paleontology- the study of fossils • Understood that extinction was part of life • Believed in catastrophism- boundaries between layers were due to catastrophes (flood, drought) and ravaged regions were populated by migrating species

  4. James Hutton • Geologist • Sought to explain the past by looking at what currently happens. He said the processes that formed the earth are still working on it and observable today • Believed in gradualism-changes in the earth were due to slow and continuous processes.

  5. Charles Lyell • Geologist, friend to Darwin • Theory of Uniformitarianism-geologic processes are so constant that their rates and effects are balanced over time • Earth must be very old to allow for these to take place • Very slow changes that persist over time can produce substantial changes

  6. Jean Baptiste de Lamarck • Published his theory in 1809 • He said evolution is driven by an organism’s innate desire for perfection

  7. Lamarck’s incorrect ideas: 1. The Law of Use and Disuse: • Parts of body used become stronger with use, those not used will deteriorate • Most famous example he used was giraffes that had to stretch their necks to feed gradually became long necked.

  8. 2. Inheritance of acquired traits- modifications acquired in the organism’s lifetime would be passed on to its offspring.

  9. Thomas Malthus-mathematician • Studied populations • Showed that resources grow linearly but populations grow geometrically • Predicted that as the human population increased we would run out of resources

  10. Charles Darwin • Dropped out of medical college • Had a consuming interest in nature • Signed on as naturalist on H.M.S. Beagle when 22 yrs. old. The voyage lasted 5 years.

  11. Galapagos Islands: • He found species that existed no where else but were similar to species in S. America • He recorded 13 species of finches-each has different beak. Each is adapted to different food

  12. He realized species change by a gradual accumulation of adaptations to different environments. • A single species of finch was separated by a channel of water and developed into 2 populations. Each was adapted to its own environment.

  13. Darwin’s idea of Natural selection: • There is an unequal ability of individuals to survive and reproduce • Variations in traits affect an individual’s ability to get resources it needs • The environment will select which traits are the most fit to survive

  14. Darwin wrote wrote the Origin of the Species but was afraid to publish it because of the uproar it would cause.

  15. A contemporary, Alfred Wallace, wrote to Darwin and wanted to publish his own idea of natural selection.

  16. Darwin came out with his book the next year and received credit for evolution as he had more evidence for it.

  17. Ideas on evolution in Darwin’s book: • Descent with modifications-all organisms are related to each other by descent from an unknown ancestor in the long ago past • Over millions of years organisms accumulated adaptations that served to make them fit for a specific way of life • Evolution explains the diversity and unity in life • Organisms over reproduce (more eggs and sperm are produced than needed, more offspring made than will survive)

  18. Evidence for Evolution I. Geological evidence: fossils The fossil record shows: • Prokaryotes are the oldest fossils • There is a chronological order of appearance in the vertebrates (fish amphibians reptiles birds mammals • Transitional forms link older fossils to newer ones

  19. Fossil evidence for evolution in horses

  20. II. Biogeographic evidence-geographic distribution of a species • Modern species are where they are because they evolved from ancestors that inhabited those same regions. • Example: • Sugar gliders and flying squirrels—even though they look alike and live in similar environments the sugar gliders are related to marsupials and the squirrel is a placental mammal

  21. III. Comparative anatomy-anatomical similarities between species in the same categories 1. Homologous structures-same structures but have different functions. Example: forelimbs of mammals

  22. 2. Analogous structures-have the same function but are different structures • Example-bird wing and butterfly wing

  23. 3. Vestigial organs-structures of marginal or no use to an organism • Whales lack hind limbs but have vestigial bones there, human appendix, human ear muscles. • It is not efficient to provide food, oxygen and space to an organ that no longer has a function

  24. Third eyelid • Ear muscles • Tailbone • Wisdom teeth • Appendix

  25. IV. Embryological evidence • Closely related organisms go through similar stages in their embryonic development • Gills, tails

  26. V. Molecular biology • The more closely related 2 organisms are the more alike their biochemistry is • Shows that all forms of life are related to some extent. Even bacteria and humans have some proteins in common.

  27. VI. Artificial selection • Deliberately selecting plants and animals to breed for specific traits produces changes in the population of that species. Process mimics natural evolution.

  28. Natural selection: • Darwin’s 5 observations: • Overproduction of offspring • Populations tend to remain stable in size • Environmental resources are limited • Individuals in a population vary in their characteristics • These characteristics are inherited

  29. Your fitness is your ability to pass on your genes • What effects your fitness? • Your survival • Your longevity (one mating or several?) • Early maturity *You have to consider the whole organism—an individual may have a weak trait but overall be more fit to survive than another.

  30. Fitness shows as 3 types of selection: 1. Directional • Shifts frequency curve in one direction or the other by favoring what was once rare

  31. Examples of directional selection: a. Pepper moths come in 2 forms-black and white • Industrial areas had trees thick with soot. This made the black moth more fit to survive. The country had whiter trees. The white moth was more fit for survival there.

  32. b. Bacterial resistance to antibiotics • Each time penicillin is used most but not all bacteria are killed. The survivors have a genetic resistance to penicillin that is passed on to their offspring. This creates new strains that we cannot fight. c. Insect resistance to pesticides (same idea as bacterial resistance)

  33. 2. Stabilizing • Acts against extreme phenotypes, favors the most intermediate individual • reduces variation • seen when environments are not changing

  34. 3. Disruptive • Environmental condition vary so that both extremes are favored

  35. Key ideas about Natural Selection: • It cannot produce perfection. You can only alter existing structures. • Adaptations are often compromises (seals move on land and water but aren’t best adapted for either • There is an element of chance. When the wind blows seeds to an island it doesn’t just select the best seeds

  36. Some types of adaptations 1. Protective coloration a. camouflage

  37. 2. Aposematic coloration bright colors serve as a warning example-poison arrow frogs Nature knows bright colors mean danger

  38. 3. Mimicry-one species bears a resemblance to another species a. Batesian mimicry-a harmless or palatable species mimics a harmful or unpalatable example-monarch and viceroy butterflies

  39. In order to work, models must outnumber the mimics

  40. b. Mullerian mimicry-harmful species mimics another harmful species examples: insects with yellow and black stripes large numbers send the message that this pattern is bad and to avoid anything with it

  41. 4. Deceptive coloration-fake eyes, false heads

  42. 5. Symbiotic adaptations-two organisms living together and/or evolving together a. Commensalism- (+,0) One benefits and one is unaffected. Example-shark and remora. Shark is not helped or hurt. The remora gets a free ride and left over food

  43. b. Mutualism- (+,+) • Relationship is beneficial to both • Examples-cleaning animals

  44. c. Parasitism (+, -) • One benefits and the other (host) is harmed • May live inside or outside host

  45. Causes of Population Diversity • Microevolution-small changes that occur from generation to generation 1. Natural selection-survival of the fittest • The most favorable traits get passed on 2. Mutations-create new alleles • They are passed on if they occur in the gametes

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