VI. Role-play

Choose one of the following situations to act out.

1. A lecturer is explaining to a group of post-graduates (which can be the whole class) a classic example of population balance. The group can then ask questions.

1. You and your colleague are discussing a huge diversity of parasitic organisms which is ecologically important in population control.

1. A reporter is interviewing a young scientist about balances between an organism and several natural enemies.

1. Two environmentalists are speaking about what is commonly ob­served: animals killed by hunters are generally healthy.

5. Two scientists are backing up the argument that a given natural enemy is capable of limiting the prey or host population to a cer­tain density. They are enumerating the most prominent points.

5. A scientist from the United States is lecturing a group of Russian students (which can be the whole class) about territoriality. The group can then ask questions.

5. You are explaining to your colleague the obvious advantage of ter­ritoriality. He is asking you whether territoriality changes the basic principle of population.

5. A scientist from the United States and one from another country (you choose which one) are discussing history of wars between na­tions that have involved territorial disputes.

5. A person who has a piece of land with a fence around is arguing with someone who hasn't about defending himself against the threat of territorial encroachment by his neighbor.

VII. FOR DISCUSSION AND COMPOSITION

Choose one of the following to discuss or write about.

1. Describe some specific mechanisms that provide population bal­ance in nature.

1. Tell about population balance between the lynx and hares as ob­served in Canada from 1850 to 1930.

1. Describe a huge diversity of parasitic organisms. What may be in­fected by parasites?

1. Do parasitic organisms act in the same way as large predators? Prove

this.

5. Do you agree that the animals killed by large predators are infected with parasites? And what about animals killed by hunters?

5. What factors have a great damping effect on the rise and fall of the prey population?

7. Describe what may occur when a species from one region is intro­duced into another.

7. What another factor is often involved in the control of carnivore and some herbivore population?

7. Tell about territoriality. What does it refer to? Discuss with exam­ples.

8'

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Unit Eight

Ecosystems: Mechanisms of Population Balance

109

10. Is the territory defended large enough? If so, why? How does the territory defended vary?

10. Discuss the obvious advantage of territoriality. Discuss with exam­ples.

10. Is territoriality an instinctive behavioral trait in many species? What does it help to maintain? Discuss.