What are the basic plans of body in animal groups?

There is great diversity in the shape, structure, appearance in the body of different animals.However, the animals can be divided into three basic plans. These plans are shown below:
(1) The cell aggregate plan : It is found in the simple animals i.e., sponges. In these clusters of cells with a rudimentary division of labour is found in them.There are no tissues or organs. Nervous system is s also absent in them.
(2) The blind sac plan: It is found in coelenterates and flat worms. These animals have a digestive cavity with only one opening to the outside. Through this opening, food is ingested and undigested waste is are called symmetrical.
(3)The tube within a tube plan:It is found in more complex forms.In this plan body cavity forms one tube within which is situated another tube the alimentary canal;opening on one side by mouth and the other side of anus.