Answer to Question #67597 in Biology for Sana

Question

In Hydra and Planaria mouth involves in both ingestion and egestion. Give reason .

Answer 1

In Hydra and Planaria, the digestive system has only one opening. Two openings develop later during evolution of more complex organisms, such as annelids. Presence of a single opening forces it to function as both mouth and anus, resulting in food intake and egestion.