Exercises
I. Reading comprehension
1. What is the main idea of the article?
a. In natural ecosystems all of the mechanisms are working in concert.
b. It is necessary to focus on one mechanism at a time.
с There are some specific mechanisms that provide population balance in nature.
Ecosystems: Mechanisms of Population Balance
2. What is a classic example of population balance?
a. between the cat family and the rabbit family
b. between the lynx predator and the hare population с between the lynx and hares
3. According to paragraph 2, surviving hares are those that
a. are best able to escape from the lynx
b. provide harder hunting for the lynx с are healthiest
4. In paragraph 3, parasites may infect
a. microbes b. all species of plants с animals
5. How do parasite organisms act in terms of population balance (para graph 3)?
a. as large predators b. as viruses с as vectors
6. In paragraph 4, parasites may
a. weaken their host с not kill their host
b. make it more vulnerable
7. What are balances between an organism and several natural ene mies (paragraph 4)?
a. unstable с less prone to wide fluctuations
b. much more stable
8. What is extremely important to recognize in all balances (para graph 5)?
a. a high degree of adaptation of the natural enemy
b. a low degree of adaptation of both the prey or host
с a high degree of adaptation of both the prey or host and the natural enemy
9. According to paragraph 5, when a species from one region is intro duced into another there may occur
a. automatic balances с lack of balances
b. ecological disasters
10. What is often involved in the control of carnivore and some herbi vore populations, according to paragraph 6?
a. the excess carnivore population с territoriality
b. some herbivore population
11. In paragraph 6, the territory defended is
a. small b. large с wide
12. Which of the following is not true?
102 Unit Eight
Ecosystems: Mechanisms of Population Balance
103
a. Territories
are larger in good times.
b. Territories are smaller in lean times.
с The size of the territory varies with resources available.
13. Put the following sentences in the correct order (paragraphs 7, 8).
a. Territoriality is an instinctive behavioral trait in many species.
b. Those individuals unable to claim a territory generally meet an unhappy end.
с Territoriality does not change the basic principle of population being a dynamic balance between biotic potential and environmental resistance.
14. According to paragraph 8, throughout history, virtually all wars be tween nations have involved
a. territorial encroachment
b. territorial disputes
с the most sophisticated weaponry available
15. What do almost all of us aspire to owning (according to para graph 8)?
a. a fence b. a piece of land с a neighbor
II. Vocabulary
From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once.
in the same way |
in terms of |
be upset |
escape |
in the face of |
ecological disasters |
lag time |
infect |
damping effect |
parasites |
diminish |
fence |
behavioral trait |
abundant |
assure |
hare |
rear a brood |
food web |
aspire |
lynx |
Knowledge of these mechanisms will make us aware of how ecosystems may and the consequences that may result.
When the population is low, each hare can find food
and plenty of places.
3. Also, surviving hares are those that are healthiest and best able to from the .
4. population balance, parasitic organisms act as large
predators.
5. Almost all of us to owning a piece of land that we can put a
around and call ours, and the bigger the piece of land, the
better.
6. All species of plants, animals, and even microbes may be by
7. In a , a population of any given organism is affected by a
number of predators and parasites simultaneously.
8. Thus, the between increase in the prey population and that
of the natural enemy is .
9. These factors have a great on the rise and fall of the prey
population.
Such introductions may lead to what are commonly called _____ as balances fail.
The territory defended is large enough to the "owners" of
being able to gather enough food to successfully .
12. limited resources, however, territoriality creates a mecha nism of selecting the strongest. 13. Territoriality is an instinctive in many species.