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Darwin, Evolution, and Natural Selection

Darwin, Evolution, and Natural Selection. Scientific Theory. Social use of the word “theory” Not the same as in science Implies a hunch or a casual guess Scientific Theory 1. Highly probable explanation based on vast collections of scientific data

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Darwin, Evolution, and Natural Selection

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  1. Darwin, Evolution, and Natural Selection

  2. Scientific Theory • Social use of the word “theory” • Not the same as in science • Implies a hunch or a casual guess • Scientific Theory 1. Highly probable explanation based on vast collections of scientific data • There are relatively few scientific theories • Examples of Scientific Theories • Cell Theory • Atomic Theory • Plate Tectonic Theory • Big Bang Theory

  3. Theories of Evolution • Lamarck (1800) • Similar species descended from a common ancestor – related to fossil record • Species change by ACQUIRING traits in their lifetime • Acquired traits are NOT genes; they are things that are learned

  4. Theories of Evolution

  5. Theories of Evolution • Alfred Wallace (late 1800’s) 1. species were modified by natural selection

  6. Theories of Evolution • Charles Darwin (late 1800’s) • Background • medical and clergy student  naturalist • HMS Beagle –goal was to survey the coast of S. America (1831-1836) –Darwin collected biological & geological specimens • Read Lyell’s Principles of Geology which influenced his thinking as he observed fossils—book proposed the earth was millions of years old

  7. Theories of Evolution

  8. Theories of Evolution • On the Galapagos Islands • Different islands seemed to have their own slightly different varieties of animals • Finches had distinctive bills – 13 different species • Very similar – must have descended from a common ancestor • Related this to artificial selection

  9. Theories of Evolution

  10. Theories of Evolution • Framework for Natural Selection (1840) a. Individuals in a population show differences b. Variations are inherited c. Organisms have more offspring than can survive on available resources d. Variations that increase reproductive success will have a greater chance of being passed on than those that do not increase reproductive success

  11. Theories of Evolution Galapagos Turtle

  12. Theories of Evolution • Wrote a book – Origin of Species (1859) a. Compiled evidence for evolution and explained how natural selection might provide a mechanism for the origin of species b. 1858: another naturalist (Alfred Wallace) proposed a theory almost identical to Darwin’s—Darwin published his book a year later; evolution is only used once: on the last page!

  13. Summary • Over time, natural selection results in changes in the inherited characteristics of a population. • These changes increase a species fitness (survival rate)

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