ACT science practice test 41

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.


Corals build the habitat that is the home for the fish and other marine species that live on the reef. The corals grow by creating aragonite forms of calcium carbonate cups in which the polyp sits. Figure 6.11 identifies the anatomy of a coral polyp.

Figure 6.11

Source: http://oceanservice.noaa.gov/education/kits/corals/media/supp_coral01a.html.

Millions of photosynthetic algae, called zooxanthellae, reside inside polyp tissues. They serve as an energy source for corals as well as providing the coloration for which corals are known.

Current research indicates that increasingly acidic waters may be to blame for the decline in coral populations. Oceans absorb atmospheric carbon dioxide. Table 6.2 depicts changes to ocean chemistry and pH estimated using scientific models calculated from surface ocean measurement data.

TABLE 6.2 Ocean Chemistry and pH

Some coral become less successful at reproducing sexually in acidic waters. Studies also show links between ocean acidification and coral bleaching. Figure 6.12 summarizes the physiological responses of marine organisms to biological ocean acidification experiments done by various scientists.

Figure 6.12

Source: Data adapted from "Recognising Ocean Acidification in Deep Time: An Evaluation of the Evidence for Acidification across the Triassic-Jurassic Boundary," Sarah E. Greene, Rowan C. Martindale, Kathleen A. Ritterbush, David J. Bottjer, Frank A. Corsetti, and William M. Berelson, Earth-Science Reviews, volume 113 (1-2), copyright © 2012 by Elsevier.

1. Zooxanthenellae would logically inhabit which part of a coral?

A. Stomach
B. Basal plate
C. Outer epidermis
D. Stinging nematocyst

2. The data in Table 6.2 indicates that as the concentration of carbon dioxide in the water rises:

A. the pH decreases and the balance shifts toward bicarbonate instead of carbonate.
B. the pH increases and the carbonate ion concentration increases.
C. both the pH and the bicarbonate concentration decrease.
D. the pH increases and the balance shifts toward carbonate instead of bicarbonate.

3. Based on the information in Table 6.2, what conclusions can be drawn about ocean chemistry?

A. Future emissions of carbon dioxide are less likely to significantly impact ocean chemistry over time.
B. Increased atmospheric carbon dioxide will have little impact on the concentration of carbonate ions.
C. Chemical changes in oceans are a result of the water absorbing atmospheric carbon dioxide produced by human activities.
D. Ocean acidification is an unpredictable response that is unlikely to be linked to human activities that increase the atmospheric concentration of carbon dioxide.

4. Factors that might impact the data found in Table 6.2 include:

I. seasonal changes in temperature.

II. variations in photosynthesis.

III. runoff from rivers.

IV. fluctuations in respiration.

Which of these is likely to account for fluctuations in the geographic pH of ocean waters?

A. II
B. III
C. I and IV
D. II and III

5. The saturation horizon is a natural boundary in seawater, above which calcium carbonate (CaCO3) can form and below which it dissolves. Which species from Figure 6.12 most likely lives below the saturation horizon?

A. Corals
B. Gastropods
C. Crustaceans
D. Calcareous algae

6. Calcifying organisms that produce the calcite form of calcium carbonate, such as foraminifera, can be less vulnerable to acidification than those constructed with aragonite structures, such as corals. Which of these provides a logical explanation for these findings?

A. Aragonite is more soluble than calcite.
B. Calcite is more soluble than aragonite.
C. Aragonite saturation is farther from the surface of oceans.
D. Calcite saturation is farther from the surface of oceans.

7. Based on the information in Figure 6.12, decreased fertilization affects corals as well as:

A. echinoderms.
B. bivalves.
C. crustaceans.
D. calcareous algae.

8. In Figure 6.12, the most significant data with regard to the health of marine ecosystems is:

A. the decline in coral calcification.
B. the rise in crustacean calcification.
C. the declining metabolism of bivalves.
D. the decreased larval survival in gastropods.

9. According to Figure 6.12, which species appear to be most affected by ocean acidification?

A. Echinoderms
B. Gastropods
C. Calcareous algae
D. Crustaceans

10. Which of the following terms best describes the relationship between zooxanthellae and corals?

A. Parasitic
B. Codependent
C. Symbiotic
D. Mutualistic

11. Corals have several features that help them survive in the shallow ocean. Which part of a coral's anatomy may protect against fluctuating environmental changes such as temperature?

A. Stomach
B. Nematocysts
C. Basal plate
D. Outer epidermis

12. Some corals can reproduce in a variety of ways. Which of these methods would produce the most diverse offspring?

A. Coral fragments regenerate to form new coral.
B. Adult coral sprouts tiny buds to form new coral.
C. Adult coral divides and both pieces grow new coral.
D. Coral eggs join with coral sperm to form new coral.

13. Which of the following is most likely to result from declines in a coral polyp's zooxanthellae population?

A. Bleaching
B. Hyperpigmentation
C. Increased thermal tolerance
D. Accelerated growth of nematocysts

14. Scientists design an experiment in an attempt to predict the effect increasingly acidic seawater will have on coral reproduction. They may use the following in the experiment:

- Aquarium tanks

- Seawater

- Tap water

- Corals

- Carbon dioxide bubbles

Which experimental design will allow the scientists to investigate their hypothesis fairly and produce high-quality data for analysis?

A. Use two tanks filled with seawater and corals. Add carbon dixiode bubbles to one tank.
B. Use two tanks filled with tap water and corals. Add carbon dioxide bubbles to one tank.
C. Use two tanks filled with corals. Add tap water to one tank and seawater to the other.
D. Use three tanks filled with carbon dioxide bubbles. Add tap water and seawater to each tank.

15. Changes in the biological processes in the surface ocean water affect deeper portions of the ocean because:

A. habitats at deeper levels depend on dissolved oxygen occurring at the surface.
B. organisms living at lower ocean levels rely mainly on products created by organisms at shallow levels.
C. the pH of organisms in shallow waters is altered and becomes non-nutritious to deep-water organisms.
D. the calcification of shallow-water organisms provides an additional layer of protection that prevents predation.