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.

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).

Stanley Miller – In 1953, he tested Oparin’s hypothesis 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).

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.

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

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.

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.

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.

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.

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.

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

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.

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.