USEFUL WORDS AND EXPRESSIONS. paragraph 1 paragraph 4 paragraph 7 relationships additional vulnerable to predation ability adults

I. READING COMPREHENSION

1. What is the main idea of the article?

a. One may already foresee the result of the interplay between bio­tic potential and environmental resistance.

Unit Seven

Ecosystems: What Keeps Them the Same?

b. No forces or rigid structures exist that prevent ecosystems from

changing, с Human impacts readily result in extinction because they are

not density-dependent.

2. Each species in an ecosystem exists as

a. a population

b. an interbreeding group
с reproductive rate

3. Maintaining or increasing a population depends on

a. recruitment

b. reproductive rate

с the early growth stages

4. The biotic potential of the species is referred to as

a. the ability of animals to migrate

b. defense mechanisms

с resistance to adverse conditions and disease

5. Environmental resistance is referred to as

a. one or more abiotic factors

b. one or more biotic factors

с the combination of all abiotic and biotic factors that may limit population increase

6. Environmental resistance effectively reduces

a. any population increase

b. the replacement level
с recruitment

7. In certain situations environmental resistance may

a. cause mortality

b. effect reproduction

с block a population's growth

8. The result of a dynamic balance between population's biotic po­
tential and environmental balance is

a. biotic potential remains constant

b. a population growth remains stable
с a population growth decreases

9. Populations remain within a certain size range because <

a. population growth ceases or declines

b. environmental resistance becomes more intense

с most factors of environmental resistance are density-depen­dent

10. Human impacts result in

a. ecosystem destruction

b. habitat alteration
с extinction

11. The biotic potential of many species depends on

a. a pack of wolves

b. a school offish

с a minimum population base

II. VOCABULARY