Question

Which of the following characteristics is true for Obelia?
A. Metagenesis
B. Morphogenesis
C. Apolysis
D. Pedagogy

Answer 1

Obelia is a eukaryotic organism which belongs to the kingdom Animalia. Their life-cycle consists of both medusa and polyp stages.

Complete answer:Obelia is an aquatic organism with a simple body structure. It takes two forms polyp and medusa through its life cycle. They are diploblastic organisms which show the presence of true two tissue layers called the epidermis and gastrodermis. The area between the two true tissue layers is filled with jelly-like mesoglea. They consist of nerves with no ganglia or brain. The digestion begins in the gastrovascular cavity and later becomes intracellular. The digestive system of Obelia is incomplete and hence, the food enters, gets ingested and expelled out through the same opening. The mode of reproduction of the polyp colony is by asexual. Obelia is confined to substrate surfaces during this stage. Individual hydrants called gastrozooids are present on the mature colonies which aid in the growth of the organism by feeding. The reproductive polyp called gonozooids has medusa buds. The sexual mode of reproduction in Obelia begins when the medusae are released from the gonozooids which produce only male medusae velum with gonads, tentacles, and mouth. Sperm and egg are released by the medusae which fuse to form a zygote which later converts into a blastula. A swimming larva called planula is formed from the blastula. Since the life cycle of the Obelia is of the alternating type which produces by both sexual and asexual reproduction, metagenesis is the true characteristics of Obelia. Metagenesis refers to the type of life cycle that occurs in plants and animals which have distinct diploid asexual and haploid sexual stages. The organism which shows the presence of metagenesis characteristics produces by both sexual and asexual modes. The life cycle of such plants and animals are of complex type.
So, option A is the correct answer.

Note:Obelia is a genus of hydrozoans, a class of mainly marine and some freshwater. Hydrozoa belongs to the phylum Cnidaria. The medusa stage of Obelia species is common in coastal and offshore plankton around the world.