In terms of complexity, how do coelomates compare to pseudocoelomates?

Coelomates are organisms that possess a true coelom, which is a fluid-filled body cavity completely lined by mesodermal tissue. This structural feature allows for more sophisticated and complex body plans and organ systems. The presence of a coelom enables the development of advanced features such as a more complex circulatory system, a more organized arrangement of internal organs, and greater flexibility for movement. Organ systems can operate more independently and efficiently because the coelom acts as a cushion for organs, allowing them to move and grow without restriction.

In comparison, pseudocoelomates have a body cavity that is not fully lined by mesoderm but is instead partially bordered by mesoderm and partially filled with fluid. While pseudocoelomates have some organizational advantages, they do not have the same level of structural complexity and independence among organs as coelomates do.

Hence, the correct answer highlights the greater complexity associated with coelomates due to their true coelomic structure, which supports a higher degree of specialization in body systems compared to pseudocoelomates.