ACT science practice test 28

Directions: Each passage is followed by several questions. After reading a passage, choose the best answer to each question and fill in the corresponding oval on your answer document. You may refer to the passages as often as necessary.

You are NOT permitted to use a calculator on this test.


The majority of scientists agree that global temperatures are rising, leading to a host of climate changes that will produce significant worldwide effects over time. Still subject to debate are the type and severity of effects that these climate changes will have on various industries. Two scientists present their viewpoints regarding the effects of climate change on agriculture in the United States.

Scientist 1

Climate change is likely to have mixed effects on U.S. agriculture over time. Every crop has a set of optimal conditions under which it grows and reproduces best. For many crops, the growth rate increases as temperature increases, suggesting that the progressive increase in average temperatures will have a beneficial effect on many types of crops. On the other hand, a faster growth rate means less time for the seeds of certain crops to mature, hindering their reproductive ability. Average temperatures will eventually surpass the optimal growth temperature for some crops, causing their yields to decline.

Crop yields also increase with carbon dioxide levels. The positive growth effect of carbon dioxide can be suppressed, however, if the optimal growth temperature is surpassed. The potential effects of climate change on other environmental conditions, including soil moisture, nutrient levels, and water availability must be taken into account as well.

Scientist 2

Agriculture in the United States will be adversely affected by climate change over the next several decades. Many weeds, pests, and fungi thrive in warm, wet climates and with increased levels of carbon dioxide. As average temperatures continue to increase and these conditions become more widespread, the habitat ranges for these organisms will spread northward. This will pose challenges to northern crops that have not previously been exposed to certain competitors and pests.

The predicted increase in extreme weather events will also negatively impact crop yields. An increase in the frequency of floods will destroy crops and potentially deter farming along major waterways altogether. In areas in which drought conditions are projected to become more common, a water supply capable of sustaining even modest crop yields is a very real concern.

1. According to Scientist 1, how will a change in average temperature affect the growth rates of crops?

A. As average temperature increases, all crops will begin to grow faster.
B. A change in average temperature will benefit some crops and harm others.
C. If average temperature changes too quickly, many crops will stop growing.
D. An increase in average temperature will hinder growth until crops adapt.

2. If Scientist 1 is correct, which of the following trends will most likely occur over the next several decades?

A. The agriculture industry will experience no significant change in crop yields.
B. The depletion of soil nutrients will cause yields of all crops to decline.
C. Crops with chemical defenses against pests will exhibit increased yields.
D. Crops with higher optimal growth temperatures will produce greater yields.

3. Which environmental change was discussed by Scientist 2, but not Scientist 1?

A. Elevated carbon dioxide levels
B. Increasing average temperatures
C. Limited water availability
D. Increased frequency of flooding

4. Scientist 2 did not predict that climate change would cause an increase in which of the following factors affecting crop yields?

A. Fungi
B. Pests
C. Seeds
D. Weeds

5. Based on the passage, the major difference between the opinions of Scientists 1 and 2 is that:

A. Scientist 2 does not predict any positive effects of climate change on agriculture.
B. Scientist 1 discusses the effects of increased temperature but not carbon dioxide.
C. Scientist 2 expects agriculture in southern areas to be unaffected by climate change.
D. Scientist 1 focuses only on the effects of climate change on crop reproductive rates.

6. Scientist 2 states that high:

A. carbon dioxide levels will benefit crop yields.
B. carbon dioxide levels will lead to decreased crop yields.
C. average temperatures will improve crop yields.
D. average temperatures will hinder the growth of fungi.

7. An industry-wide increase in agricultural pesticide use over the next several decades would support the opinion of:

A. Scientist 1.
B. Scientist 2.
C. both scientists.
D. neither scientist.

8. According to Scientist 1, what happens when a crop's optimal growth temperature is surpassed?

A. The crop maintains growth at its maximum rate.
B. The crop continues to grow but at a reduced rate.
C. The crop experiences growth at an exponential rate.
D. The crop can no longer grow in that environment.

9. Based on the information in the passage, both scientists would agree with which of the following statements?

A. The greatest threat posed by climate change to the U.S. agriculture industry is the projected increase in extreme weather events.
B. Southern crops are better adapted than northern crops to withstand the effects of elevated carbon dioxide levels associated with climate change.
C. The effects of climate change will have a greater negative impact on the reproductive ability of crops than on their growth rate.
D. Increasing average temperatures associated with climate change will provide an advantage to some organisms.

10. It can be inferred that Scientist 1 believes elevated levels of carbon dioxide will directly lead to crops with a(n):

A. shortened growing season.
B. higher optimal growth temperature.
C. decreased need for soil nutrients.
D. increased rate of photosynthesis.

11. Which of the following does Scientist 2 identify as potential competitors to northern crops?

A. Invasive species of weeds
B. Newly introduced crop species
C. Other industries that use land
D. Migrating pest species

12. The hypothesis of Scientist 1 could best be tested by recording data over the next decade on:

A. crop yields, average temperatures, and soil nutrient availability worldwide.
B. seed production, soil nutrient availability, and water availability worldwide.
C. seed production, carbon dioxide levels, and water availability in the United States.
D. crop yields, average temperatures, and carbon dioxide levels in the United States.

13. If Scientist 2 is correct, over time, the range of:

A. northern crops will become narrower.
B. southern crops will move farther south.
C. northern crops will overtake southern crops.
D. southern crops will remain constant.

14. Assuming that increasing carbon dioxide levels cause average temperature to increase, which graph best represents the relationship between carbon dioxide level and crop yields, according to Scientist 1?

A.
Figure 2.1
B.
Figure 2.2
C.
Figure 2.3
D.
Figure 2.4