Name: Class Mammalia and Its Characteristics
Uploaded: 2019-07-19
Duration: 4 min 10 s
Description: "Endoskeleton is common among all my creatures; mammary glands are one of my key features! Who am I?" Watch and find out for yourself! Are you ready?

Question

Write an account on polymorphism in Cnidarians.

Accepted Answer

Cnidaria or Coelenterata is a phylum that belongs to the group of invertebrate animals. These animals have a tissue level of organisation, are diploblastic and exclusively marine animals, except a few. They possess a special group of defensive cells called cnidoblasts or stinging cells thus are named as cnidarians.

These animals exist in two forms: Polyps and Medusae.

Polyps are the sessile and cylindrical forms the mouth of which faces upwards and is surrounded by the tentacles. These are formed by asexual reproduction mostly by budding. e.g in Hydra and Adamsia.

Medusae are the umbrella-shaped forms that have their mouth facing downward. These are the sexual forms and bear male and female gonads. e.g. Aurelia, Physalia.

The polyps produce medusoid forms by vegetative reproduction and the medusae forms polyps by sexual reproduction. This phenomenon of alteration of generation is called polymorphism. Since cnidarians complete their life cycle in two stages, they are said to exhibit metagenesis.

Write an account on polymorphism in Cnidarians.

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