2011 15 ppt evolution and natural selection

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2011 15 ppt evolution and natural selection

  1. 1. History of Evolutionary ThoughtBefore 1850, most people believed…– Earth formed by supernatural events and never changed.– Earth only a few thousand years old.– Each species was made to fit its environment.– Species never changed and did not go extinct.
  2. 2. History of the Idea of Evolution Jean Baptiste Lamarck Proposed that species DO evolve ***PROPOSED EVOLUTION OCCURRED BY INHERITANCE OF ACQUIRED CHARACTERISTICS
  3. 3. LamarckLamarck’s Hypothesis:1. Desire causes changeEx.) ancestors of birds had a desire tofly, so they did.2. Use and DisuseEx.) If species used its arms to swimover and over, it would develop flippers.If not, flippers would disappear.3. Traits acquired during life can bepassed on Ex.) Michael Jordan’s children will begreat basketball players. WRONG!!!!
  4. 4. History of the Idea of EvolutionAlfred Wallace English teacher who collected plants and insects. Observed variations in organisms Proposed that species DO change over time
  5. 5. Charles Darwin At 22, sailed on the “HMS Beagle” to the Galapagos Islands. Was going to school to be a minister-believed God created each species to match its habitat and they never changed. Thought Earth was about 6,000 years old and didn’t change.
  6. 6. Charles Darwin cont. During journey, he made observations and recorded them in a journal. Darwin began to doubt that species remained “constant.”
  7. 7. Scientific TheoriesHypothesis: a testableexplanation for an observation“Theory” in layman’s terms = aguess and this is NOT the sameas a scientific theory.Scientific theory: Accepted as factual NO EVIDENCE AGAINST IT!
  8. 8. EvolutionEVOLUTION IS A SCIENTIFICTHEORY! Not a hypothesis, or an educated guess Unending amount of evidence to support itEvolution is called “theunifying principle of Biology”Isnt Evolution JUST a Theory?
  9. 9. Types of EvolutionEvolution - genetic change of a population of organismsover time- descent with modification Microevolution: Small genetic changes of a population Can occur in shorter amount of time
  10. 10. Natural Selection Natural selection: process by which organisms best suited to their environment survive and reproduce.– Darwin’s proposed mechanism of evolution– Nature “selects” which members of a species will succeed in struggle for existence.– Survival depends on the particular environmental conditions a species finds itself in.– If the environment changes, so do the populations that live there. Adaptation: using inherited genetic characteristics to increase chance of survival in new environment.
  11. 11. Natural SelectionThree conditions necessary for natural selection to occur:1. Genetic variation: Individuals within a population must be genetically different. This is due to mutation. ****Random mutations are the raw material for evolution to occur!!!!!!!1. Overproduction of offspring: More organisms are born than can survive.2. Differential reproduction: Certain traits enable individuals to survive and have more offspring than others.—SURVIVAL OF THE FITTESTResult: Genes that help a species survive stay in the gene pool. “Unfavorable” genes gradually decrease. This causes changes in gene frequencies EVOLUTION!!!!! Evolution: How Does Evolution Really Work?
  12. 12. Natural Selection ExampleThe industrial revolution– In England in the early 1800’s industry boomed– Factories, trains, smoke and smog– Peppered moths were dark or light colored, and the dark ones that were once rare became more common.– Hypothesis?
  13. 13. The Peppered Moth– Kettlewell tested this hypothesis Released equal numbers of moths in polluted AND clean forests. In industrialized areas, dark gray moth was better camouflaged. They survived, had more offspring– The population *as a whole* evolved to be better suited to the environment more gray and camouflagedADAPTATION!– This is an example of microevolution
  14. 14. The Peppered Moth
  15. 15. Types of Natural Selection1. Directional selection2. Stabilizing selection3. Disruptive selection
  16. 16. Types of Natural SelectionDirectional selection- individuals at one end ofthe curve are favored so they contribute moreoffspring so the curve shifts in one direction .Directional selection
  17. 17. Types of Natural SelectionStabilizing selection- average individuals arefavored so the middle of the curve increases.Stabilizing Selection
  18. 18. Types of Natural SelectionDisruptive selection- individuals at both extremesare favored so they contribute more offspring andtwo peaks result over time.Disruptive selection
  19. 19. Darwin and the FinchesDarwin traveled to the Galapagos andtook interest in the finches.He noticed the finch species on theislands were different, but all resembledone from S. America.Darwin thought some migrated and newspecies evolved. This is what heproposed:
  20. 20. Darwin’s Finches Finches migrated from S. America to the islands – Populations on different islands adapted to different environments and food sources they found there. – Microevolution and mutations accumulated so populations on the different islands became more and more different. Divergence: the accumulation of differences between species or populations.
  21. 21. Darwin’s FinchesOver time the populations on the islands becameso different they no longer mated-different species – Several new finch species evolved from a common ancestor from S. America – Speciation: the formation of a new species through accumulated changes. – This is an example of macroevolution
  22. 22. Another Example of SpeciationGeographical isolation: members of apopulation are separated geographically leads to speciation.– Due to volcanoes, earthquakes, flooding, etc.– Can lead to divergence and then speciation.
  23. 23. Artificial SelectionArtificial selection: human intervention in animal orplant reproduction to ensure that certain desirabletraits are represented in successive generations.Instead of NATURE selecting which traits arefavorable, HUMANS select the favorable traits. Ex. dogs or racehorses

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