Question

In Hydra, waste material of food digestion and nitrogenous waste is removed from
(a)Mouth
(b)Body wall
(c)Mouth and body wall
(d)Mouth and tentacles

Answer 1

Hint: There is no anus in Hydra and also it has neither blood and blood vessels, nor organs of excretion. Due to the thin form of the body wall and circulation of water in the gastrovascular cavity, most cells of the body remain freely exposed to the surrounding water.

Complete answer:
In Hydra, undigested residues or wastes are ejected out from the coelenteron through the mouth, while the nitrogenous excretory product (ammonia) is removed from the general body surface. They lack the organ level organisation, and they have a tissue level of organisation. They have a gastrovascular cavity which helps for the digestion and absorption.

Additional Information: -Hydra is commonly called as a blind gut or blind sac because food enters and wastes excreted through the same passage.
-The Hydra's body is radially symmetrical with an adhesive foot called the basal disc.
- Few tentacles are present at the opening of the mouth which secrete chemicals to capture the prey.
-Hydra is diploblastic, and so it is with two body layers: the epidermis (outer layer), and gastrodermis (inner layer).
-The gastrodermis lines the region of the stomach.
-The extracellular digestion occurs inside the central cavity of the sac-like body of the hydra.
-The process of respiration and excretion occurs by the diffusion through the epidermal surface.
-The larger waste products are excreted out through the mouth rather than the use of an anus.

So, the correct answer is, ‘Mouth and body wall.’

Note: Linnaeus gave the name Hydra, a Greek word that means water serpent on the basis of its ability to regenerate its lost parts. Hydra belongs to the Phylum Cnidaria and to the class Hydrozoa. They have a unique characteristic feature by which attracts the biologists, that is their regenerative ability. They do not age or die at all. They are composed of different stem cells inside the body column to renew or regenerate themselves. If Hydra is cut into several pieces then each piece has a capacity of development to a complete Hydra. This ability of growth and development for hydra from its pieces is called regeneration.