Question

Assertion [A]: Obelia exhibits metagenesis.
Reason [R]: Obelia exists in both polyp and medusa form.

• A. Both [A] and [R] are true and [R] is the correct explanation of [A]
• B. Both [A] and [R] are true but [R] is not the correct explanation of [A]
• C. [A] is true but [R] is false
• D. Both [A] and [R] are false

Answer 1

The correct option is A Both [A] and [R] are true and [R] is the correct explanation of [A]

Many cnidarians exhibit metagenesis or alternation of generations. Obelia is a good example of this. The life history of Obelia includes both asexual and sexual generations that alternate with each other to complete the life cycle. The sedentary polyp is a colonial form, that alternates with the free-swimming medusa phase. The polyp colony reproduces by asexual budding. The medusa buds get detached from the parent colony, and become free-swimming sexual forms that carry ova and sperms in their respective gonads, and release them into the water. They then fertilise to form a zygote, which later morphs into a blastula, then a ciliated swimming larva called a planula. The planula eventually attaches to a substrate and gradually develops into a polyp colony.