Plants and animals will find it difficult to escape from or adjust to the effect of global warming. Scientists have already observed shifts in the lifecycles of many plants and animals, such as flowers blooming earlier and birds hatching earlier in the spring. Many species have begun shifting where they live or their annual migration patterns due to warmer temperatures.

With further warming, animals will tend to migrate toward the poles and up mountainsides toward higher elevations. Plants will also attempt to shift their ranges, seeking new areas as old habitats grow too warm. In many places, however, human development will prevent these shifts. Species that find cities or farmland blocking their way north or south may become extinct. Species living in unique ecosystems, such as those found in polar and mountaintop regions, are especially at risk because migration to new habitats is not possible. For example, polar bears and marine mammals in the Arctic are already threatened by dwindling sea ice but have nowhere farther to go.

Projecting species extinction due to global warming is extremely difficult. Some scientists have estimated that 20 to 50 percent of species could be committed to extinction with 2 to 3 Celsius degrees of further warming. The rate of warming, not just the magnitude, is extremely important for plants and animals. Some species and even entire ecosystems, such as certain types of forest, may not be able to adjust quickly enough and may disappear.

Ocean ecosystems, especially fragile ones like coral reefs, will also be affected by global warming. Warmer ocean temperatures can cause coral to "bleach", a state which if prolonged will lead to the death of the coral. Scientists estimate that even 1 Celsius degree of additional warming could lead to widespread bleaching and death of coral reefs around the world. Also increasing carbon dioxide in the atmosphere enters the ocean and increases the acidity of ocean waters. This acidification further stresses ocean ecosystems.

Question 4: The phrase "dwindling sea ice" in paragraph 2 refers to:

A. the frozen water in the Artie. B.the violent Arctic Ocean.

C. the melting ice in the Arctic. D.the cold ice in the Arctic.

Question 5: It is mentioned in the passage that if the global temperature rose by 2 or 3 Celcius degrees_____________ .

A. half of the earth's surface would be flooded.

B. the sea level would rise by 20 centimeters.

C. water supply would decrease by 50 percent.

D. 20 to 50 percent of species could become extinct.

Question 6: According to the passage, if some species are not able to adjust quickly to warmer temperatures, ___.

A. they may be endangered B.they can begin to develop

C. they will certainly need water. D.they move to tropical forests.

Question 7: The word fragile in paragraph 4 most probably means .

A. very large B.easily damaged

C. rather strong D. pretty hard

Question 8: The bleaching of coral reefs as mentioned in paragraph 4 indicates

A. the water absorption of coral reefs. B.the quick growth of marine mammals.

C. the blooming phase of seaweeds. D.the slow death of coral reefs.

Question 9: The level of acidity in the ocean is increased by .

A. the rising amount of carbon dioxide entering the ocean.

B. the decrease of acidity of the pole waters.

C. the extinction of species in coastal areas.

D. the loss of acidity in the atmosphere around the earth.

Question 10: What does the passage mainly discuss?

A. Influence of climate changes on human lifestyles.

B. Effects of global warming on animals and plants.

C. Global warming and possible solutions

D. Global warming and species migration.