Chapter 17: The History of Life



The relationship between time and the decay of radioactive 40K to 40Ar: Uranium-235 decays to lead-207 with a half-life of 713 million years. If you analyze a rock and find that it contains uranium-235 and lead-207 in a ratio of 3:1, how old is the rock?

1. Diagram, or label a diagram, of the experimental apparatus of Stanley Miller and Harold Urey. Explain the function of teach part of the apparatus. How would the experiment’s result change if O2 were included in the spark chamber?

2. Describe how Miller and Urey's experiments with a hypothetical early Earth atmosphere helped to propose how life formed on Earth.

3. How do we know that the earliest organisms were anaerobes?

4. What are ribozymes, and what does their existence suggest about the role of RNA in the prebiotic world

5. Discuss why RNA is considered by many scientists to have been the basis for early forms of life.

6. What are microspheres, and what does their existence suggest about the origin of the first living cells?

7. What were the first photosynthetic organisms like?

8. Beginning about 2.2 billion years ago, the concentration of oxygen gas in the Earth's atmosphere rose significantly. Where did the oxygen come from, and how did it get there?

9. Why was the rise of oxygen in the Earth's atmosphere both a crisis and an opportunity for life at the time?

10. Describe how eukaryotes could have arisen, given that Earth was inhabited only by prokaryotic cells

11. Scientists have identified a living bacterium believed to be descended from the endosymbiont that gave rise to mitochondria. Would you expect the DNA sequence of this modern bacterium to be most similar to the sequence of DNA from a plant chloroplast, an animal cell nucleus, or a plant mitochondrion?

12. What were the first multicellular organisms, and what specific advantages did their multicellularity have?

13. Why might it be more advantageous for an organism to be multicellular than unicellular?

14. Why do biologists believe that the early evolution of animals produced many types that have no current descendants?

15. What were some of the major obstacles that stood in the way of living beings moving onto dry earth?

16. . What was the importance of the evolution of plant pollen?.

17. Explain how amphibians are only partially adapted to a terrestrial existence.

18. What are some of the bodily features that humans share with early primates?

19. What are some of the causes of mass extinctions that have been proposed? Do they all have the same cause?

20. Why does human cultural evolution occur more rapidly than biological evolution

21. The diagram below is meant to depict the history of Earth on a 24-hour clock face. Using this analogy, place the events below at their proper "time" in history.

22. The diagram below indicates the probable origin of mitochondria and chloroplasts. Label each of the steps in this process.

23. Using the evolutionary tree below as a guide, label the indicated species of human.

24.

As humans evolved, their use of tools became more sophisticated. Identify the genus and species of human that is responsible for the creation of each of these tools.

25. There are two theories on the evolution of Homo sapiens. Label these two correctly using the diagram on the left.

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