1. 17.2 Clues About Evolution Mr. Perez

2. Important Vocabulary  Review vocabulary  Epoch  Sedimentary rock  Radioactive element  New Vocabulary  Embryology  Vestigial structure  Homologous

3. Clues from Fossils (recap)  Most of the evidence for evolution comes from fossils.  Most fossils are found in sedimentary rocks  The fossil record provides evidence that living organisms have evolved  Relative dating vs. Radiometric dating  Relative dating uses the principle of superposition to figure out the age of fossils (does not give absolute age, only relative)  Radiometric dating uses an estimate age of the rock by comparing the amount of radioactive element with the amount of nonradioactive element in the rock. (absolute age)

4. Fossils and Evolution (recap)  Fossils provide a record of evidence of organisms that live in the past, however, the fossil record is incomplete because some animals do not become fossils

5. More Clues about Evolution  Embryology  Homologous structures  Vestigial structures  DNA

6. Embryology  The study of embryos and their development  An embryo is the earliest growth stage of an organism A tail and pharyngeal pouches are found in the embryos of: Fish Reptiles Birds Mammals Fish develop gills Tails remain in: Reptiles Birds Some mammals These similarities suggest an evolutionary relationship among all vertebrates (animals with backbones)

7. Embryology

8. Homologous structures  Body parts that are similar in structure and origin  Can also be similar in function  Often indicate that two or more species share common ancestors

9. Vestigial structures  Structures that don’t seem to have a function  Example: manatees, snakes and whales no longer have back legs, but still have a pelvic bone  Example: the appendix in the human body serves no purpose  Scientists hypothesize that these structures once served a function in an ancestral species

10. DNA (deoxyribosenucleic acid)  The molecule that controls heredity and directs the development of every organism  Found in chromosomes in the nucleus  Scientists can use DNA to:  Compare the similarities with other species (similar ancestry)  Determine how closely related organisms are

11. Classwork questions 1. Compare and contrast relative dating and radiometric dating. 2. Explain how DNA can provide some evidence of evolution. 3. Compare and contrast the five types of evidence that support the theory of evolution.

12. Videos  http://www.pbs.org/wgbh/evolution/educators/teachstuds/sv ideos.html http://www.pbs.org/wgbh/evolution/educators/teachstuds/sv ideos.html

13. Resources  Florida Science Grade 8 Glencoe Science & McGraw Hill Publishing  Google Images