Question:
Which of the following statements is correct in relation to molluscs?
Which of the following statements is correct in relation to molluscs?
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Nudibranchs are shell-less molluscs due to evolutionary loss.
Updated On: Jun 20, 2026
- Internal shell is present in Aplysia and shell is absent in Doris
- Internal shell is present in Doris and absent in Aplysia
- Torsion is found in Unio
- Shell of octopus contains eight transverse plates
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The Correct Option is A
Solution and Explanation
Step 1: Understanding molluscan diversity.
Molluscs show variation in shell presence and body organization.
Step 2: Characteristics of Aplysia.
Aplysia (sea hare) possesses a reduced internal shell.
Step 3: Characteristics of Doris.
Doris (nudibranch) completely lacks a shell due to evolutionary loss.
Step 4: Evaluating other options.
- Torsion occurs in gastropods, not Unio.
- Octopus does not have transverse shell plates.
Step 5: Biological reasoning.
Evolution in molluscs leads to shell reduction or loss in some groups.
Step 6: Final conclusion.
Thus, only statement (1) is correct.
Molluscs show variation in shell presence and body organization.
Step 2: Characteristics of Aplysia.
Aplysia (sea hare) possesses a reduced internal shell.
Step 3: Characteristics of Doris.
Doris (nudibranch) completely lacks a shell due to evolutionary loss.
Step 4: Evaluating other options.
- Torsion occurs in gastropods, not Unio.
- Octopus does not have transverse shell plates.
Step 5: Biological reasoning.
Evolution in molluscs leads to shell reduction or loss in some groups.
Step 6: Final conclusion.
Thus, only statement (1) is correct.
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