1. Darwin, Evolution, and Natural Selection

2. Scientific Theory A.Social use of the word “theory” 1.Not the same as in science 2.Implies a hunch or a casual guess B.Scientific Theory 1. Highly probable explanation based on vast collections of scientific data 2.There are relatively few scientific theories C.Examples of Scientific Theories 1.Cell Theory 2.Atomic Theory 3.Plate Tectonic Theory 4.Big Bang Theory

3. Theories of Evolution A.Lamarck (1800) 1.Similar species descended from a common ancestor – related to fossil record 2.Species change by ACQUIRING traits in their lifetime 3.Acquired traits are NOT genes; they are things that are learned

4. Theories of Evolution

5. B.Alfred Wallace (late 1800’s) 1. species were modified by natural selection

6. Theories of Evolution C.Charles Darwin (late 1800’s) 1.Background a.medical and clergy student  naturalist b.HMS Beagle –goal was to survey the coast of S. America (1831-1836) –Darwin collected biological & geological specimens c.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. 2.On the Galapagos Islands a.Different islands seemed to have their own slightly different varieties of animals b.Finches had distinctive bills – 13 different species c.Very similar – must have descended from a common ancestor d.Related this to artificial selection

9. Theories of Evolution

10. 3.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 4.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!

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