1. KEY CONCEPT The origin of life on Earth is a topic that has generated great amounts of study.

2. Earth was very different billions of years ago. Name some differences that you know. There have been many hypotheses of Earth’s origins. The most widely accepted hypothesis of Earth’s origins is the nebula hypothesis. A swirling cloud of gas was drawn together due to gravity, forming our sun. Remaining debris circled the sun and, through repeated collisions, formed the planets.

5. Lipid molecules spontaneously form membrane-enclosed spheres.

7. Microbes have changed the physical and chemical composition of Earth. How? The oldest known fossils are a group of marine cyanobacteria. prokaryotic cells added oxygen toatmosphere deposited minerals

8. Symbiosis What is symbiosis? If two organisms become so dependent upon each other that they cannot survive alone, is it possible they could merge into one life form? What if it becomes more advantageous to the survival of the offspring if both organisms multiply at the same time?

9. Eukaryotic cells may have evolved through endosymbiosis. Break it down… what do you think endosymbiosis means? Endosymbiosis is a relationship in which one organism lives within the body of another. Mitochondria and chloroplasts may have developed through endosymbiosis.

10. Why are geologists able to estimate the age of rock strata using index fossils? A. Index fossils formed only in certain kinds of rocks. B. Two methods of dating need to be used to date rock strata. C. The organisms that formed index fossils lived for long periods of time. D. The organisms that formed index fossils lived only during a specific time period.

11. Why are geologists able to estimate the age of rock strata using index fossils? A. Index fossils formed only in certain kinds of rocks. B. Two methods of dating need to be used to date rock strata. C. The organisms that formed index fossils lived for long periods of time. D. The organisms that formed index fossils lived only during a specific time period. Correct Answer = D During which period did all existing animal phyla develop? A. Devonian B. Triassic C. Cambrian D. Jurassic

12. Why are geologists able to estimate the age of rock strata using index fossils? A. Index fossils formed only in certain kinds of rocks. B. Two methods of dating need to be used to date rock strata. C. The organisms that formed index fossils lived for long periods of time. D. The organisms that formed index fossils lived only during a specific time period. Correct Answer = D During which period did all existing animal phyla develop? A. Devonian B. Triassic C. Cambrian D. Jurassic Correct Answer = C

13. What events help geologists define where one period ends and another begins? A. Adaptive extinctions B. Mass extinctions C. Major earthquakes D. Bursts of radioactivity from the Sun

14. What events help geologists define where one period ends and another begins? A. Adaptive extinctions B. Mass extinctions C. Major earthquakes D. Bursts of radioactivity from the Sun Correct Answer = B

16. There are different theories as to how the first amino acids came to be

17. The Miller-Urey experiment resulted in amino acids being formed after passing electricity through gases

18. The meteorite hypothesis suggests that the original amino acids came from outer space

19. There are different theories as to how the first cells formed

20. Iron sulfide bubbles theory

21. Lipid membrane theory

22. Cyanobacteria are the oldest fossils and may have given the concentrations of oxygen needed for sustaining life on Earth

23. Eukaryotic cells may have arisen from endosymbiosis