Question

5. What is the necessity to have a circulatory system in animals?​

Answer 1

Answer:

The circulatory system varies from simple systems in invertebrates to more complex systems in vertebrates. The simplest animals, such as the sponges (Porifera) and rotifers (Rotifera), do not need a circulatory system because diffusion allows adequate exchange of water, nutrients, and waste, as well as dissolved gases.

Answer 2

Answer:

they can digest any thing