Compare a complete digestive system to a gastrovascular cavity. what is the evolutionary value of the system?

The gastrovascular cavity is a structure found in primitive animal phyla. It is responsible for both the digestion of food and the transport of nutrients throughout the body. The cavity has only one opening to the environment. Food goes in and waste comes out that same opening, making it a two-way digestive tract.

By contrast, organisms that have a mouth on one end with an anus on the other end have a one-way digestive tract, called an alimentary canal. Food goes in the mouth, while waste comes out the anus.