Question

5. Your lob partner tells you that Cnidarians and Platyhelminthes are said to have very similar methods of digestion. Is this statement true or false? Explain your answer based on your observation of both the hydra eating the daphnia in comparison to the planarian eating the egg yolk.

Answer 1

Hydra has a gastro-vascular cavity, With in this cavity digestion and absorption of food occurs. They do not have a separate gut. The cells lining the gastro-vascular cavity (gastrodermis cells) they release enzymes and digest the food partially outside and then absorb the partially digested food. Digestion of the food completes with in the cells. So digestion is partially extra cellular and partially intracellular. It is unique to Cnidarians or Hydra. In all other animals, digestion is extracellular only. No itracellular digestion occurs. Protozoans have intracellular digestion. Cnidarians are intermediate because they have partly intracellular and partly extracellular digestion.

Planaria have a separate gut in their body. Food is taken in to the gut. Digestion completes in the gut. The digested food is absorbed in to the body cells. So, digestion is completely extracellular.

The statement is false.