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Difficulty: EasyIdentifying Underlying Assumptions and Premises

### Ocean Acidification and Oysters

Two students discuss the effects of rising atmospheric carbon dioxide (CO2CO_2) on marine organisms that build calcium carbonate (CaCO3CaCO_3) shells.

Student 1
Rising atmospheric CO2CO_2 dissolves in ocean water, lowering its pH and making it more acidic. This acidic water directly dissolves the existing CaCO3CaCO_3 shells of living adult oysters, killing them. Therefore, the decline in oyster populations is driven by the chemical dissolution of their shells.

Student 2
Rising atmospheric CO2CO_2 does lower ocean pH, but this does not dissolve existing shells. Instead, the lower pH reduces the concentration of carbonate ions (CO32−CO_3^{2-}) in the water. Larval oysters require these ions to construct their shells. Without sufficient carbonate ions, larval oysters cannot build shells and die before reaching adulthood. Thus, the population decline is driven by the inability of young oysters to build new shells.

Based on the passage, both Student 1 and Student 2 assume which of the following?

  1. Rising atmospheric carbon dioxide levels lead to a decrease in ocean pH.Answer
  2. B
    Existing adult oyster shells dissolve more quickly than larval oyster shells.
  3. C
    Larval oysters are more sensitive to water temperature than to changes in pH.
  4. D
    Carbonate ions serve as the primary source of nutritional energy for larval oysters.

Answer

Rising atmospheric carbon dioxide levels lead to a decrease in ocean pH.
The correct option is correct because both Student 1 and Student 2 base their respective arguments on the foundational premise that rising atmospheric carbon dioxide levels dissolve in ocean water and cause a decrease in the pH of the ocean.

Step-by-Step Solution

1
Analyze Student 1's viewpoint for assumptions about carbon dioxide and pH.
Student 1 states that rising atmospheric CO2CO_2 dissolves in ocean water and lowers its pH.
To identify the core premises of the first argument.
2
Analyze Student 2's viewpoint for assumptions about carbon dioxide and pH.
Student 2 states that rising atmospheric CO2CO_2 does lower ocean pH.
To identify the core premises of the second argument and find common ground.
3
Compare the statements to find the shared assumption.
Both students agree and assume that the increase in atmospheric carbon dioxide causes a reduction in ocean pH.
To determine the correct choice representing the shared assumption.

Key Concept

Identifying shared underlying assumptions and premises in conflicting scientific viewpoints.
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Topics

Identifying Underlying Assumptions and Premises

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