1. Waste food must be expelled before taking the next food, otherwise there would be mixing of both.

2. The incomplete digestive tract cannot store the food.

3. It is less efficient because it serves as the function of circulatory system.

Advantage of complete alimentary canal.

1. There is no chance of mixing in digested food and waste food, because the opening for ingestion and egestion are separate.

2. For circulation of absorbed food there is circulatory system.

3. It is more efficient.