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1. Which of the following sources of energy depend ultimately on the energy of sunlight: (a) wood, (b) coal, (c) oil, (d) hydroelectric power, (e) atomic power?

2. List four different kinds of bacteria that participate in the nitrogen cycle and tell specifically what each does.

3. Why do plants need nitrates and phosphates?

4. Why is the layer of topsoil much thicker in grasslands than in the tropical rain forest?

5. The time required for organic debris (e.g., newly fallen leaves) to decay and become incorporated in the topsoil was determined in four different ecosystems: tropical rain forest, deciduous forest, taiga, and grasslands.  The values, not in the same order, were: 1 year, 3 years, 7 years, and 6 weeks.  Match the values with appropriate ecosystems.

6. What factors regulate the rate of growth of a population of animals started by a single breeding pair introduced into a new territory?  What factors limit the ultimate size of this population?

7. The fixation of nitrogen to ammonia requires approximately 147 kcal/mole of N2.  What is the minimum number of ATP molecules that you would expect to be needed for the process?  (Recent measurements indicate that the actual value is close to this.)

8. How is it possible for ecological generalists – those which, for example, feed on a wide range of foods – coexist with specialists in natural communities, as they do throughout the world? Why do all species not simply become generalists or specialists? Which of these habits is a better strategy for survival? Why?

9. How can the principle of competitive exclusion be applied to the origin of large numbers of species of certain genera in the Hawaiian Islands? What would you expect to happen in the future to the hundreds of species of Drosophila that occur there, leaving aside the possibility of their extincition through the destruction of their habitats by humans?

10. How do you think the intensity of competition would differ between an Arctic tundra and a tropical rain forest? How would you test your answer?

11. Which kinds of natural communities are most resistant to introduced species? Why?

12. Why is it more difficult to demostrate Müllerian mimicry than Batesian mimicry experimentally? How would you go about demonstrating each?

13. In Batesian mimicry, why are the mimics rare?

14. Some kinds of insects are more resistant to insecticides than others. Can you think of a reason why, based on your readings in ecology?

15. At what successional stage would you characterize a field of wheat? What does this imply as to its stability and productivity?

16. How could you increase the net primary productivity of a desert?

17. Why does the net productivity of an ecosystem increase is it becomes more mature?

18. How do you think the decomposition rates of organic matter would differ in a tropical rain forest, a temperate deciduous forest, a desert, and the tundra? How would these differences affect human existence in the area?

19. What kinds of biological communities would you expect to find on the windward and leeward sides of a mountain range in an area where the annual precipitation ranged between 20 and 100 centimeters per year and was distributed mainly in one rainy season? How would the height of the mountain range affect the situation?

20. Near the coast of southern California there are two major plant communities. Right along the ocean occurs the coastal sage community, which is dominated by low shrubs that often wither or lose their leaves in the summer. Higher up, on the ridges, occurs the chaparral, a community dominated by tall evergreen shrubs. Which of these communities would you think grows in the area that receives the most rainfall? Which grows on the better soils? Which is the more productive on an annual basis? Where would you expect to find the most annual plants?