Evolution

What is Evolution?  The theory that organisms gradually and slowly change over time into new species.  Results from natural selection acting on genetic variation present among individuals of a species  Sources of variation: mutations and genetic recombination (mutations can be good, bad, or indifferent)

Example of Evolution:  Pesticide resistance  In the 1960s DDT was used to kill mosquitoes (to stop the spread of malaria). At first, the results were good, but soon DDT use had to stop. Why?  The pesticide killed most insects, but a few survived. These survivors are mosquitoes with genes that somehow enable them to resist the chemical.  These survivors then reproduce and may pass on their pesticide resistant genes to their offspring.  In each generation, the number of pesticide resistant insects increase, making the pesticide spraying less effective.

Evidence for Evolution  Fossils-reveal changes in the characteristics of organisms  Reveals the appearance of organisms in a historical sequence  Oldest know fossils are prokaryotes (3.5 bya)  Paleontologist = scientist who studies fossils

Evidence for Evolution continued…  Comparative embryology- characteristics among different species are displayed only in embryonic development and are lost in adults  example: All vertebrates have gill pouches on the sides of the throat during embryonic development (fishes, frogs, snakes, birds, apes, humans, etc…)

Evidence for Evolution continued…  Comparative biochemistry-universal DNA!!  The four bases that make up DNA are the same in all species. The more similar the bases, the more related the organisms are. (The DNA of humans is 98% similar to that of Bonobos.) The greater number of sequences that match, the more recent the common ancestor.  The codon chart applies to all living things… the triplet bases code for the same amino acids in all living things (the process of protein synthesis is almost identical in all eukaryotes)

Evidence For Evolution  Comparative anatomy- shows that organisms have common ancestors  Homologous structures- characteristics that are similar because they were inherited from a common ancestor

Evidence for Evolution  Comparative Anatomy  Analogous structures-characteristics that are similar in purpose, because the organisms share a common role in the environment, but are not inherited from a common ancestor (example: wings of bat and wings of insects)

Homology vs Analogous

Evidence for Evolution  Vestigial structures- structures that are inherited but unused. These structures were fully developed and functional in some ancestor (example: snakes-leg and pelvic bones; horse- reduced toe; humans- appendix)

More Evidence for Evolution  All forms of life use RNA  All living things depend on water  All life is based on five elements – carbon, hydrogen, nitrogen, oxygen, and phosphorus. These elements, along with small amounts of others, make up the organic compounds common to all cells: lipids, carbohydrates, proteins, and nucleic acids