Briefly describe the process involved in this early evolutionary stage. This leads to an invagination of the organism and development of tissue layers and ultimately to specialized organs and organ systems. Describe two of these characteristics and tell how their presence in these organisms illustrates the idea of diversification from a common ancestor. Again there is a long list of possibilities - so just support your arguments. What are the main characteristics of bilateral organisms and what is significant about their form.
Bilateral organisms have a front, back, top, bottom and left and right sides.
Pseudocoelom is a fluid filled body cavity not lined with mesoderm. True coelomate has a fluid filled body cavity lined with mesoderm. The mesoderm lining of the coelomate holds the internal organs semi rigidly. This allows for individual development and protection of the organs while maintaining proper orientation. In Labrador retrievers hair color is the result of interactions of genes at two different loci.