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Evolution & Natural Selection Evolution: The change in populations over time.

Evolution & Natural Selection Evolution: The change in populations over time. Types of Evidence for Evolution:

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Evolution & Natural Selection Evolution: The change in populations over time.

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  1. Evolution & Natural Selection Evolution: The change in populations over time. Types of Evidence for Evolution: a. Fossils: Remains or traces of a once living organism. Radioactive dating is used to date them. Ex. C-14 has a half life of 5,730 yrs if you started out with 20g after one half life you have 10g.

  2. Comparing Homologous Structures: • Homologous Structures: Structural features with a common evolutionary origin. Can be similar in arrangement, function or both. • Example: Human arm, whale flipper, cat leg & bat wing.

  3. Comparing Homologous Structures: • Vestigial Structures: Structures that does not have a function in present day organism but probably useful to the ancestor. • Example: Appendix, blind mole rat, human tail bone.

  4. Comparing Homologous Structures: • Analogous Structures: Structures that do not have a common evolutionary origin but are similar in function. Evolved separately but look similar due to same environment. • Example: Insect wing & bird wing.

  5. Comparing Developmental Patterns: • Embryos look similar which supports evidence for a common ancestor.

  6. Comparing DNA & Proteins: • Comparisons of DNA & RNA of different species have the same bases and code for the same 20 amino acids. Sequences of nucleotides are used to construct evolutionary diagrams. The more similar the amino acid sequence, the more closely related.

  7. Theories of Evolution Lamark vs. Darwin Lamark: First to put forth a systematic presentation of evolution. Inheritance of Acquired Characteristics: Ex. Salamanders were unable to walk through the tall grass so they slithered on their bellies. Their leg muscles wasted away and became small and this was passed on to their offspring. Finally the legs disappeared.

  8. Giraffes stretched to reach leaves and their necks got longer

  9. Darwin: He went on a voyage on the HMS Beagle & collected biological specimens. Example: Finches in the Galapagos These observations lead to his theory and his book called “The Origin of Species” The mechanism of his theory is called natural selection, which is the process by which organisms with traits well suited to the environment survive and pass on these traits to their offspring at a greater rate than those less suited to the environment.

  10. Darwin: • Process of Natural Selection: • Living things face a constant struggle for survival. • Only strong individuals survive to reproduce. • Causes genetic changes gradually over many generations. • Species adapt or become better suited to their environment.

  11. Kettlewell’s Demonstration: Did an experiment with pepper moths. He knew that color was inherited so he took a large number of light & dark colored moths and released them into a forest where the trees were blackened by soot. He recaptured the moths & found that 2/3 of them were dark. He tested it again by releasing dark & light colored moths into a forest with light colored bark. He recaptured the moths & found that 2/3 of them were light.

  12. Therefore, the moths that were better suited to their environment were able to survive and not be eaten by the birds.

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