Paragraph 14
Desert plant populations have evolved sophisticated structural and behavioral traits that aid their survival in extremely dry
conditions.
Q. A third group actually goes so far as to protect its access to water from nearby plants.
R. For example, the creosote bush inhibits the growth of competing root systems in its surrounding soil
by producing a potent root toxin.
S. In addition to these methods of absorbing water and defending it from other plants, many such plants
are able to close tiny holes in their surfaces during the heat of day in order to protect against
evaporation.
T. Others utilize shallow but widespread roots, which allow them to absorb large but infrequent flows
of downpours.
U. Some send out long, unusually deep taproots that seek water far beneath the surface of the Earth.
14.
Paragraph 15
The construction of Glenn Canton Dam on the Colorado River has caused unforeseen environmental effects.
Q. These riverbank deposits are necessary for the creation and maintenance of sandbars, which form
natural habitats for fish.
R. It has been proposed that, if water is released from the dam annually, the flooding that results will
prevent the disappearance of these sandbars.
S. The dam prevents the annual floods that used to occur as snow in the Rocky Mountains melted and
flowed into the river.
T. Consequently, the river will be able to maintain its population of fish despite the existence of the
dam.
U. By preventing these floods, it prevents the river from stirring up sediments on the river bottom and
depositing them high on the riverbanks.
15.
Paragraph 16
Wild tiger populations in Southeast Asia have declined sharply in the last century and remain in peril of disappearance.
Q. Still, scientists believe that if the tiger is to survive in the wild at all, its best chance is in India.
R. Because of this view, the tigers remaining in India are held to be crucial to the survival of the
species.
S. Although conservation efforts have currently halted this rapid decline, the survival of the wild tiger
16.
