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[1] Humans Threaten the Biosphere The human population tends to modify existing ecosystems for its own purposes.1 Humans clear forests or grasslands in order to grow crops; later, they build houses on what was once farmland; and finally, they convert small towns into cities.2 As coasts are developed, humans send sediments, sewage, and other polllutants into the sea.3

[2] Both coral reefs and tropical rain forests are severely threatened as the human population increases in size.1 Some reefs are 50 million years old, and yet in just a few decades, human activities have destroyed 10% of all coral reefs and seriously degraded another 30%.2 At this rate, nearly three-quarters could be destroyed within 50 years.3 Similar statistics are available for tropical rain forests.4

[3] It has long been clear that human beings depend on natural ecosystems for food, medicines, and various raw materials.1 We are only now beginning to realize that we depend on them even more for the ecological services they provide.2 Just as chemical cycling occurs within ecosystems, so ecosystems keep chemicals cycling throughout the entire biosphere.3 The workings of ecosystems ensure that the environmental conditions of the biosphere are suitable for the continued existence of humans.4 And many ecologists (scientists who study ecosystems) believe that ecosystems cannot function properly unless they remain biologically diverse.5

( Mader, Human Biology, 8th edition, pp. 4-5)

1

Humans form a population in many ecosystems.
A)True
B)False
2

Many ecosystems are under pressure from human activities.
A)True
B)False
3

Humans have seriously damaged three-quarters of all coral reefs.
A)True
B)False
4

Human beings depend for their survival on ecosystems.
A)True
B)False
5

The following is an example of an ecosystem:
A)tropical rain forests
B)coral reefs
C)a small town
D)all of the above
6

Which of the following ecosystems are potentially threatened by human activity:
A)tropical rain forests
B)coral reefs
C)a small town
D)all of the above
7

Which of the following statements represents an opinion rather than a fact?
A)Some coral reefs are more than 50 million years old.
B)People clear forests in order to grow crops.
C)Destroying coral reefs is wrong.
D)Many scientists believe that, in order to survive, humans are dependent on diverse ecosystems.
8

What is the meaning of degraded as it is used in paragraph 2, sentence 2?
A)humiliated
B)damaged
C)flattened
D)polluted





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