Ch. 17 – 19 Evolution

1. Ch. 17 – 19 Evolution • Years ago people use to believe in spontaneous generation. • Examples: People believed that fish were produced from mud in a pond. Why? • We live on a changing Earth. The Earth is constantly changing. The Earth is about 4.6 billions years old.

2. Evidence of life • Fossils show that the oldest life forms are 3.5 to 3.8 billion years old. • Oparins’s Hypothesis – this soviet scientist believed the Earth first contained ammonia (NH3), hydrogen (H2), water vapor, & methane (CH4). These compounds were thought to of formed amino acids, which are important for life (proteins & DNA).

3. Stanley Miller – In 1953, he tested Oparin’s hypothesis. He did this with an apparatus that was made up of similar gases and chemicals that were on Earth 4.6 billion years ago. • The experiment generated organic compounds, including amino acids (needed for DNA).

4. The First Cells • 3.5 to 3.8 billions years ago • The first organisms were likely prokaryotic. • Thought to be heterotrophic • Anaerobic • Over time the heterotrohic cells became able to produce food with photosynthesis. • The 1st eukaryotes developed about 1 billion years ago.

5. Evolution • What is evolution? • A slow gradual change over time. • Everything evolves • Automobiles • Computers • Machines • Organisms  horse (4 to 3 to 1 toe)

6. Evidence of Evolution • 1. Homologous structures – similar in structure, but may or may not have a similar function. • Ex. Human’s arm vs. Bird’s wing • 2. Vestigial organ – has no useful function. • Ex. Appendix, ear muscle, coccyx (tail) • 3. Embryologic similarities – study the embryos of different organisms and compare the similarities.

7. 4. Biochemical similarities – comparing an organisms DNA or RNA and the amino acids and genes that make up each organism. • 5. Fossils – study old fossils with newer fossils. Scientist also carbon date fossils.

8. Natural Selection • What is natural selection? • Organisms with favorable variations (better traits) survive and reproduce at a higher rate. • “Survival of the Fittest” • Natural selection is an explanation for diversity in living and extinct life forms and the molecular similarities observed among the millions of different species.

9. If an organism developed a “new” structure that they once had thousands of years ago, would that “new” structure be the same? • No, because the “new” structure would be generated by a different genetic make-up. • What are some factors that allow organisms to evolve? • Limited amount of space and food • Offspring that are better able to survive and reproduce • Variety of organisms due to mutations and recombination of genes.

10. Why would an organism that reproduces asexually not be as successful in evolving? • The traits stay consistent from generation to generation. There are NO genetic variations in populations.

11. PLATE TECTONICS • Plate tectonics is explained by the movement of the earth’s surface with the help of convection currents that occur in the mantle. • This caused the continents to move to where they are today. • Pg. 408  Pangaea  Laurasia & Gondwana  Today

12. FOSSILS • A fossil is evidence that an organism lived long ago. Most are found in sedimentary rocks. • It shows that new life has formed and that other life forms have ceased to exist.

13. Other Scientists • Charles Darwin – one of the first scientists to publish ideas on how organisms evolved by natural selection. • “The Orgin of Species” • Jean Lamarck developed a theory that if an organism no longer used a body part, then that part may become a vestigal organ.