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About ACT Exam
Science Reasoning Sample Questions
Click
on the letter choices to determine if you have the correct answer and for
question explanations.
(An actual ACT Science Test contains 40 questions to be answered
in 35 minutes.) |
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| DIRECTIONS: The passage in this
test is followed by several questions. After reading the passage, choose the
best answer to each question and fill in the corresponding oval on your
answer document. You may refer to the passage as often as necessary.
You
are NOT permitted to use a calculator on this test. |
Abandoned
cornfields have been the sites of investigations concerning ecological
succession, the orderly progression of changes in the plant and/or animal
life of an area over time (see Figure 1).
(Note:
The plants are ordered according to their appearance during ecological
succession.)
During
the early stages of succession, the principal community (living unit)
that dominates is the pioneer community. Pioneer plants are depicted
in Figure 2.
The
final stage of ecological succession is characterized by the presence of the climax
community, the oak-hickory forest. Figure 3 depicts the gradual change
from pine to hardwoods.
Figures adapted from
Eugene P. Odum, Fundamentals of Ecology. ©1971 by Saunders College
Publishing/Holt, Rinehart, and Winston, Inc. |
| 1. |
On the basis of
the data presented in Figure 1, approximately 80 years after the
abandonment of cropland, the land would contain: |
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A. |
pine seedlings
only. |
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B. |
oak-hickory
hardwood forests only. |
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C. |
early invading
species like horseweed, aster, and broomsedge. |
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D. |
large pine trees
with an understory of hardwood trees. |
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| 2. |
According to the
information in Figure 3, a 150-year-old climax community would contain oak
and hickory trees with a density of approximately: |
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F. |
3,000 trees per
unit area. |
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G. |
5,000 trees per
unit area. |
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H. |
15,000 trees per
unit area. |
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J. |
20,000 trees per
unit area. |
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| 3. |
On the basis of
the data depicting the gradual change from pine forest to an oak-hickory
forest, after 100 years, as the density of the pine trees: |
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A. |
increases, the
density of the oak-hickory trees increases. |
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B. |
increases, the
density of the oak-hickory trees decreases. |
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C. |
decreases, the
density of the oak-hickory trees increases. |
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D. |
decreases, the
density of the oak-hickory trees decreases. |
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| 4. |
Given the
information in Figure 1, which of the following conclusions concerning
ecological succession in an abandoned cornfield is most correct? |
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F. |
Succession in an
abandoned cornfield begins on bare rock. |
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G. |
Succession is
characterized by the replacement of one plant community by another until a
climax community has been achieved. |
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H. |
The height of the
plants in the communities decreases as succession progresses to the climax
stage. |
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J. |
The plant species
change continuously during succession, but the change is more rapid in the
later stages than in the earlier stages. |
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| 5. |
According to
Figure 2, pioneer plant(s) showing a progressive increase in summed
diameter of stems per unit area over the course of several years of
succession is(are): |
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A. |
horseweed only. |
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B. |
broomsedge only. |
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C. |
aster and
broomsedge only. |
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D. |
horseweed, aster,
and broomsedge. |
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