Biology 156



Biology 156 9 Apr 2001

Evolutionary Ecology Bob Podolsky

Week 13. Evolution of early life

Study guide

After the module on origins of life, you should be able to:

Lecture 13.1. Origins of life: what and when

1. Sketch out a brief timeline for the history of the Earth, including the formation of the universe, galaxy, solar system, Earth's crust, and the earliest records of life

2. Describe general characteristics that can be used to distinguish living from non-living matter

3. Distinguish between what are meant by the "cenancestor" and the "primordial form"

4. Give evidence from genetics and cell biology for the hypothesis that there was one ancestor common to all currently living organisms, and describe a hypothetical piece of evidence that, if uncovered, would go against the hypothesis

5. Draw a highly simplified phylogeny of the three major kingdoms of life, showing the positions of prokaryotic/eukaryotic organisms and multicellular/unicellular organisms

6. Explain why and how information contained in ribosomal RNA was used to develop this phylogeny

7. Use this diagram to develop an argument for what some traits of the cenancestor were

8. Explain how molecular information was used to propose that endosymbiosis was important in the evolution of the eukaryotes

9. Explain what Sleep et al.'s study of large impacts on the Earth suggest about the lower bounds for when the Earth might have been habitable for life

10. Explain what the deposition of apatite (calcium phosphate) crystals indicates about the possibility of life's origins on Earth

11. Explain what evidence sets an upper bound on the origin of life on Earth

Lecture 13.2. Origins of life: how and where

12. Describe the steps necessary to account for the evolution of living matter

13. Describe Miller's hypothesis and experimental test of an idea about the origins of simple building blocks on earth, and one potential problem with his experiment that he helped to later identify

14. Give an alternative hypothesis for the appearance of simple organic building blocks on Earth

15. Explain why Ferris et al. used clay particles to examine the assembly of simple building blocks into polymers (Fig 11.21 refers to increases in the length of nucleotide polymers in the presence of clay particles)

16. Explain the chicken-or-egg dilemma posed by trying to understand the origins of nucleic acid replication

17. Describe how Bartel and Szostak's work with ribozymes suggests a possible solution to the dilemma

18. Argue for how the timing of life on Earth, the probability of intelligent life on other planets, and the probability that life could survive interstellar travel suggest that life may have originated elsewhere and been transported to Earth, either accidentally or not

19. Explain why, if life originated on Earth, the early atmosphere would not have been as conducive as the current atmosphere to life forming near the Earth's surface

20. Describe how the results of Cleaves and Miller suggest a possible solution to the problem posed in #19

21. Explain what the work of Baross and Hoffman suggests about an alternative scenario for where life may have originated, why this environment might have been conducive to the formation of life, and why it might not have been

22. Explain why two particular locations in the solar system (outside the Earth) have been the focus of the search for extraterrestrial life

23. Suggest why life has probably not continued to originate throughout the evolutionary history of the Earth

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