What is the difference between blind sac plan and tube-within-tube plan in animals?
There are three body plans in an animals. Body plan is the structural arrangement of organs inside the body of an animal.These include cell aggregate plan, blind sac plan, tube-within a tube plan.
*Blind sac plan includes animals having just a single pore opening to the exterior in their digestive system. Food is taken in and the undigested food leave the body through a common pore. Division of labour is exhibited by the cells. e.g. Coelenterates and Flat worms.
*Tube-within-a tube plan includes complex organisms which have two openings one on either side of the digestive system. One opening is for ingestion and the other for egestion. As the food travels from one opening to the other, there occurs, digestion nd absorption processes. e.g. all the complex organisms like human beings.