How does an animal’s body plan reflect its ecology?
An animal’s body plan can be described through its nervous system, symmetry, cephalization and body cavity.
Animals may have complex and organized nervous systems, a diffuse arrangement of neurons in a nerve net, or no nerve cells at all. As organisms increase in nervous complexity, they also show greater body control and more complex sensory systems, social structures, mate choices and feeding patterns.
Animals may be asymmetric, radially symmetric or bilaterally symmetric. Only the Porifera lineage of organisms may be asymmetric, and they are the most simple of animals. Radially symmetric animals are also relatively simple. Commonly, they do not have a centralized nervous system and are only found floating freely or attached to a substrate in water environments. All other animals are bilaterally symmetric and are found in a variety of conditions.
Cephalization is the development of an anterior region, or a head, where several important structures are located. A concentration of nervous tissue in this area is called a brain, where information processing can occur. This is also often the location of the mouth and other sensory organs. This development is often associated with an increase in complexity for bilaterally symmetric organisms.
Animals may be acoelomates, pseudocoelomates, or coelomates. Acoelomates do not have a body cavity to store organs. Instead, each organ is set in place, but this causes a restriction in movement. Any bend in body shape also bends organ shape. Pseudocoelomates have partially lined body cavity and coelomates have cavities that are entirely lined. Greater motility is possible with a more protected cavity.