Question

Why do many water animals not have a well developed blood system?​

Answer 1

Step-by-step explanation:

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. ... Instead, gases, nutrients, and wastes are exchanged by diffusion.

Answer 2

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. Instead, gases, nutrients, and wastes are exchanged by diffusion.