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Difficulty: EasyCommand of Evidence: Textual

Marine biologist Dr. Sarah Jenkins investigated the factors influencing the growth of giant kelp (MacrocystisMacrocystis pyriferapyrifera) off the coast of California. Jenkins hypothesized that giant kelp grows more rapidly in cooler ocean currents because these currents carry higher concentrations of dissolved nitrogen, a critical nutrient that the species requires to build cellular structures. She contrasted this with kelp growth in warmer, nutrient-depleted waters.

Which finding, if true, would most directly support Jenkins’s hypothesis?

  1. Giant kelp specimens in cool, nitrogen-rich waters grew significantly faster than giant kelp specimens in warm, nitrogen-poor waters.Answer
  2. B
    Giant kelp forests provide critical habitats for many species of fish and marine invertebrates.
  3. C
    Giant kelp probably evolved the ability to absorb nitrogen through its blades because it cannot survive in deep ocean zones where nutrients are scarce.
  4. D
    Marine plants in general depend on dissolved nutrients from ocean currents to complete their life cycles.

Answer

The finding that giant kelp specimens in cool, nitrogen-rich waters grew significantly faster than giant kelp specimens in warm, nitrogen-poor waters.
The correct answer directly supports the hypothesis by comparing two environments and showing that the group in the cool, nitrogen-rich water grew faster than the group in the warm, nitrogen-poor water, establishing a direct connection between the conditions described in the hypothesis and the predicted outcome.

Step-by-Step Solution

1
Identify the core claim or hypothesis in the passage.
The researcher hypothesizes that giant kelp grows faster in cooler waters due to the higher abundance of dissolved nitrogen.
To evaluate textual evidence, we must first establish the exact relationship that needs to be supported.
2
Analyze each option to see if it provides direct evidence showing that cool, nitrogen-rich water leads to faster growth.
The option comparing specimens in cool, nitrogen-rich water to those in warm, nitrogen-poor water confirms a positive growth difference linked to these factors.
This establishes the factual basis that supports the proposed causal mechanism.
3
Eliminate options that are speculative, too broad, or unrelated to the hypothesis.
Options concerning habitat provision, evolutionary speculation, or marine plants in general are ruled out.
These options do not test or validate the specific claim about giant kelp growth rates in cool, nitrogen-rich conditions.

Key Concept

Command of Evidence: Textual
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Command of Evidence: Textual

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