Explain Coelomates?
Recall that Acoelomates have solid bodies, and Pseudocoelomates have body cavities that form between the endoderm and the mesoderm. In contrast, the body cavity of Coelomates forms from within the mesoderm tissues themselves.
In evolutionary terms, this allowed much more complex digestive, circulatory, and reproductive systems to evolve. For instance, the digestive tract was thereafter not limited to the length of the body, but could fold back upon itself, forming convolutions that allowed more thorough digestion and greater absorption. A fluid-filled body cavity also permitted a true circulatory system, freeing the organism from the limitations of diffusion between itself and the environment.