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5. Which tree species is an early-succession species in North 8. Which letter in the diagram represents the latest stage of
American forests? aquatic succession?
(a) beech (a) A
(b) fir (b) B
(c) aspen (c) C
(d) maple (d) D
6. Which of the following best describes an environmental 9. Which of the following best explains the progression of
problem associated with a sudden decrease in the popula- events depicted in the diagram?
tion of a keystone species in an ecosystem? (a) The process of succession in an aquatic ecosystem can
(a) A sudden decrease in population of a keystone species occur over thousands of years as sediment slowly fills
is always caused by human activities. in a body of freshwater.
(b) The loss of a keystone species will cause a sharp (b) The process of primary succession occurs in a fresh-
increase in the primary production in an ecosystem. water ecosystem after sediment has filled in a body of
(c) A sudden decrease in the population of a keystone spe- water.
cies will result in increased gene flow in a population. (c) Aquatic succession takes place over millions of years
(d) The loss of a keystone species can have a cascading effect and gives rise to new aquatic species.
on the populations of other species in its food web. (d) Aquatic succession takes place more quickly than ter-
restrial succession.
7. Which describes an indicator species?
(a) a species that has a large effect on other species in the Free-Response Question
community
(b) a species that suggests the presence of human sewage Many bats in the state of Pennsylvania play a critical part in
(c) a species that serves as a pioneer species in succession maintaining the state’s ecosystems. As the primary predators of
(d) a species that serves as a climax species in succession night-flying insects, bats play a significant role in controlling
insect populations. As such, they can be considered keystone
Use the diagram below to answer questions 8 & 9: species for their enormous economic value as biological con-
trol agents of insects, valued in the multi-millions of dollars
each year.
(a) Identify the trophic level of these bats. (1 pt.)
(b) Describe how these bats can be considered a keystone
species. (1 pt.)
A (c) Explain how this ecosystem in Pennsylvania might be
affected if a disease suddenly decreased the bat popula-
tion. (2 pts.)

Researchers estimate that the loss of bats would raise agri-
Time culture costs by about $75 per acre, in terms of the pesticides
B needed to replace them. In 2014, this was estimated to cost the
state of Pennsylvania $300 million.

(d) Calculate the number of acres of farmland affected by
the loss of bats. Show all work. (2 pts.)
(e) Calculate the cost per hectare of farmland, if there are
C approximately 0.4 acres in one hectare. Show all work.
(2 pts.)
(f ) In 2014, the population of Pennsylvania was 12.79
million people. Calculate the cost per capita in
Time Pennsylvania of the pesticides needed to replace the
Grasses pest control service of the bats. Show all work. (2 pts.)
and shrubs
Wet center

D

ModUle 14 ■ Ecological Succession 161
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