Question

The phenomenon where Cnidarians exhibit an alternation of generation is called

• A. Parthenogenesis
• B. Metagenesis
• C. Gametogenesis
• D. Sporogenesis

Answer 1

Answer:

B. Metagenesis

Phylum Cnidaria (Coelenterata):

• They are aquatic, mostly marine, sessile (attached) or free-swimming
• Radially symmetrical animals
• Cnidarians exhibit tissue level of organization
• They are diploblastic
• The name cnidaria is derived from the cnidoblasts or cnidocytes (which contain the stinging capsules or nematocytes) present on the tentacles and the body.
• Cnidarians exhibit two basic body forms called polyp and medusa.
• The Polyp is a sessile and cylindrical form like Hydra, Adamsia, etc. whereas, the Medusa is umbrella-shaped and free-swimming like Aurelia or jelly fish.
• Those cnidarians which exist in both forms exhibit alternation of generation (Metagenesis), i.e., polyps produce medusae asexually and medusae form the polyps sexually (e.g., Obelia).

Examples:

• Physalia (Portuguese man-of-war)
• Adamsia (Sea anemone)
• Pennatula (Sea-pen)
• Gorgonia (Sea-fan)
• Meandrina (Brain coral)