Blind San plan:

In this plan, the body is sac like with a digestive cavity which opens to outside by only one aperture, which functions as mouth and anus. The cells are more specialised with division of labour. This type of type of body organisation is exhibited by coelenterates and flat worms.

Tube within-a tube-plan:

This type of body plan is found in more complex animal groups. The animals with this body plan posses a digestive canal having two openings at the ends. The openings at the anterior end is mouth through which food enters the digestive canal, at the posterior end anus is present meant for ingestion of undigested waste matter. The digestive canal; is present inside the body cavity and hence, this body plan is termed as the tube within a tube.