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Difficulty: EasyLogical Inferences

Parrotfish are herbivorous marine animals that feed primarily on algae covering coral reefs. By scraping algae off the coral, parrotfish prevent algae from overgrowing coral colonies, which would otherwise suffocate and die. However, parrotfish grazing also accidentally removes small portions of the calcium carbonate skeleton of the coral itself. In reefs with very high parrotfish populations, the rate of skeletal erosion exceeds the rate of new coral growth. Which choice most logically completes the text?

  1. A
    the parrotfish will continue to protect the coral from being suffocated by algae.
  2. B
    the algae populations on the reef will grow out of control and kill the coral.
  3. the total volume of the coral reef's physical structure will decrease over time.Answer
  4. D
    the parrotfish will migrate to find a different food source to prevent reef damage.

Answer

the total volume of the coral reef's physical structure will decrease over time.
The correct answer is directly supported by the relationship outlined in the passage: when the rate of skeletal erosion exceeds the rate of new coral growth, the net physical result is a decline in the overall coral skeleton volume over time.

Step-by-Step Solution

1
Identify the primary effects of parrotfish grazing on coral reefs as described in the passage.
Parrotfish protect coral by consuming algae, but their grazing also removes portions of the coral skeleton.
To establish the dual mechanical and biological impact of parrotfish grazing on the coral.
2
Analyze the condition specified in the passage for reefs with high parrotfish densities.
The rate of skeletal erosion from grazing is greater than the rate of new coral growth.
To find the mathematical relationship between the physical loss and gain of coral structure.
3
Determine the logical outcome of this relationship.
Because erosion exceeds growth, the net result must be a physical decline in the reef structure over time.
To choose the option that directly completes the text without relying on external assumptions.

Key Concept

Logical Inferences
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Topics

Logical Inferences

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