Useful words and expressions

paragraph 1	in a systematic way	overlap
biota	low point
biotic structure	growth	paragraph 6
abiotic factors	stressed	law of limiting factors
	injury	overwatering
paragraph 2		overfertilizing
interplay	paragraph 4	pitfall
extremes	maximum growth	growing season
average	optimal range	drought
acidity	entire span
salinity	range of tolerance	paragraph 7
in response to	limits of tolerance	restricting
	zones of stress	application
Paragraph 3	general pattern	predation
key observation		agricultural crops
thrive	paragraph 5	constant struggle
tolerate	result in	weeds
shade	freezing temperatures	pests
chamber	life cycles

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Unit Four

Ecosystems: What They Are

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paragraph 8

aquatic terrestrial as a result certain bounds

spread paragraph 9

influence altering

volition ripple effect

large scale verge evidence

Exercises

I. Reading comprehension

1. What is the main idea of the article?

a. The biosphere consists of a great variety of environments, both aquatic and terrestrial.

b. Every ecosystem has two "sides": the organisms on one hand and the environmental factors on the other.

с Humans have changed and are continuing to change things on a very large scale.

2. According to paragraph 2, the environment involves the interplay of

a. rainfall, temperature, light, water and wind

b. chemical nutrients, pH, salinity and fire

с many physical and chemical, or abiotic factors

3. The difference in response to environmental factors determines

a. which organisms do or don't survive

b. which species may or may not occupy a given region с the degree to which each is present or absent

4. In paragraph 3, the principle that different species thrive under dif­ ferent conditions applies to

a. laboratory experiments

b. a series of chambers in which all abiotic factors are controlled с all living things, both plants and animals

5. According to paragraph 4, there are zones of stress between

a. the high and low ends of the range of tolerance

b. the maximum growth and an optimal range

с the optimal range and the high and low limit of tolerance

6. Every species (both plant and animal) has

a. the high or low limit of tolerance

b. an optimum range and zones of stress

c. limits of tolerance with respect to every abiotic factor

7. Many plants may grow under

a. different conditions

b. the same conditions с optimal conditions

8. Which paragraph discusses the Law of Limiting Factors?

a. Paragraph5.

b. Paragraph 6. с Paragraph?.

9. The Law of Limiting Factors includes

a. any factor that affects the organism

b. the problem of "too little" с the problem of "too much"

10. In paragraph 7, the Law of Limiting Factors was first presented

a. in connection with the observations regarding the effects of chemical nutrients on plant growth

b. by Justus von Liebig с in 1840

11. Liebig's Law of Minimums may be applied to

a. our agricultural crops

b. biotic factors

с all abiotic factors

12. In paragraph 8, each environment with the species it supports is

a. anecotone

b. an ecosystem

с a unique grouping of organisms

13. Every ecosystem is interconnected with others through

a. certain bounds of limiting factors

b. ecotones

с some species that cross from one system to another

14. Humans have changed and are continuing to change things on a very large scale (paragraph 9). What will these changes bring?

a. The extinction of thousands of species.

b. Manifold changes over most of the earth.

с A sudden and catastrophic "collapse of the biosphere".

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Unit Four

Ecosystems: What They Are

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