Question

Assertion (A): Adult gastropods are asymmetrical though they are included in phylum Mollusca.
Reason (R): Symmetry of organism is determined in early developmental stages but not in adults.

• A. Both A and R are correct and R is the correct explanation of A
• B. Both A and R are correct but R is not the correct explanation of A
• C. A is correct but R is incorrect
• D. A is incorrect but R is correct

Hint:

Gastropod asymmetry is due to torsion, not the timing of developmental symmetry.

Answer 1

The Correct Option is C

- Assertion (A) is correct: Adult gastropods, such as snails, undergo a developmental process called torsion, which leads to asymmetry in the adult form. This is a characteristic feature of this class in phylum Mollusca.
- Reason (R) is incorrect: While it's true that some aspects of body structure are established early in development, symmetry itself is initially bilateral in molluscs, and the asymmetry in gastropods is due to a specific later-stage developmental process (torsion), not simply general developmental timing. Hence, A is true but R is not.