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Difficulty: MediumCommand of Evidence: Quantitative

Marine biologist Dr. Sofia Rossi and her team investigated the resilience of two key Caribbean reef-building coral species, *Acropora cervicornis* and *Porites astreoides*, under elevated sea surface temperatures. Corals rely on calcification to build their calcium carbonate skeletons, a process that is often impaired by thermal stress. Rossi hypothesized that while both species would exhibit reduced calcification rates when exposed to heat stress, the structurally denser *Porites astreoides* would demonstrate greater thermal tolerance, maintaining a significantly higher calcification rate than *Acropora cervicornis* at elevated temperatures.

Mean Calcification Rates of Two Coral Species at Different Temperatures:

Coral speciesCalcification rate at 27∘C27^\circ\text{C} (mg CaCO3 cm−2 day−1\text{mg CaCO}_3\text{ cm}^{-2}\text{ day}^{-1})Calcification rate at 31∘C31^\circ\text{C} (mg CaCO3 cm−2 day−1\text{mg CaCO}_3\text{ cm}^{-2}\text{ day}^{-1})
*Acropora cervicornis*1.851.850.450.45
*Porites astreoides*1.151.150.950.95

Which choice most effectively uses data from the table to support Dr. Rossi's hypothesis?

  1. A
    Under baseline conditions of 27∘C27^\circ\text{C}, the calcification rate of *Acropora cervicornis* was 1.85 mg CaCO3 cm−2 day−11.85\text{ mg CaCO}_3\text{ cm}^{-2}\text{ day}^{-1}, which was higher than the rate of 1.15 mg CaCO3 cm−2 day−11.15\text{ mg CaCO}_3\text{ cm}^{-2}\text{ day}^{-1} for *Porites astreoides*.
  2. At 31∘C31^\circ\text{C}, the calcification rate of *Porites astreoides* was 0.95 mg CaCO3 cm−2 day−10.95\text{ mg CaCO}_3\text{ cm}^{-2}\text{ day}^{-1}, whereas the rate for *Acropora cervicornis* was 0.45 mg CaCO3 cm−2 day−10.45\text{ mg CaCO}_3\text{ cm}^{-2}\text{ day}^{-1}.Answer
  3. C
    At 31∘C31^\circ\text{C}, the calcification rate of *Acropora cervicornis* was 0.95 mg CaCO3 cm−2 day−10.95\text{ mg CaCO}_3\text{ cm}^{-2}\text{ day}^{-1}, whereas the rate for *Porites astreoides* was 0.45 mg CaCO3 cm−2 day−10.45\text{ mg CaCO}_3\text{ cm}^{-2}\text{ day}^{-1}.
  4. D
    At 31∘C31^\circ\text{C}, the calcification rate of *Porites astreoides* was 0.95 mg CaCO3 cm−2 day−10.95\text{ mg CaCO}_3\text{ cm}^{-2}\text{ day}^{-1}, suggesting that its denser skeletal structure will allow it to expand its habitat range as ocean temperatures rise.

Answer

At 31∘C31^\circ\text{C}, the calcification rate of *Porites astreoides* was 0.95 mg CaCO3 cm−2 day−10.95\text{ mg CaCO}_3\text{ cm}^{-2}\text{ day}^{-1}, whereas the rate for *Acropora cervicornis* was 0.45 mg CaCO3 cm−2 day−10.45\text{ mg CaCO}_3\text{ cm}^{-2}\text{ day}^{-1}.
The correct answer accurately states the data from the table for the elevated temperature of 31∘C31^\circ\text{C}. At this temperature, the calcification rate of *Porites astreoides* (0.95 mg CaCO3 cm−2 day−10.95\text{ mg CaCO}_3\text{ cm}^{-2}\text{ day}^{-1}) is indeed higher than that of *Acropora cervicornis* (0.45 mg CaCO3 cm−2 day−10.45\text{ mg CaCO}_3\text{ cm}^{-2}\text{ day}^{-1}), which directly supports Dr. Rossi's hypothesis that *Porites astreoides* maintains a higher rate under thermal stress.

Step-by-Step Solution

1
Identify Dr. Rossi's hypothesis in the passage.
The hypothesis is that under heat stress, the structurally denser *Porites astreoides* will maintain a higher calcification rate than *Acropora cervicornis*.
This establishes what evidence is required: a comparison of calcification rates between the two species at the elevated temperature.
2
Locate the elevated temperature data in the table.
The elevated temperature is 31∘C31^\circ\text{C}. Under this column, the rate for *Acropora cervicornis* is 0.45 mg CaCO3 cm−2 day−10.45\text{ mg CaCO}_3\text{ cm}^{-2}\text{ day}^{-1}, and the rate for *Porites astreoides* is 0.95 mg CaCO3 cm−2 day−10.95\text{ mg CaCO}_3\text{ cm}^{-2}\text{ day}^{-1}.
This extracts the correct quantitative parameters needed to evaluate the claim.
3
Select the option that accurately states these figures and compares them in a way that supports the hypothesis.
The correct option states that the rate of *Porites astreoides* (0.950.95) is higher than that of *Acropora cervicornis* (0.450.45) at 31∘C31^\circ\text{C}.
This directly confirms the prediction that *Porites astreoides* is more thermally tolerant.

Key Concept

Command of Evidence: Quantitative
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Command of Evidence: Quantitative