BIO153H5 Chapter Notes - Chapter 33: Parthenogenesis, Oligochaeta, Arthropod
Document Summary
Protostomes are bilaterally symmetric, triploblastic, coelomate animals. Protostomes are a monophyletic group comprising two major lineages: lophotrochozoa and ecdysozoa (figure 33. 3). The 14 phyla of lophotrochozoans include molluscs, anelids, and flatworms. The name lophotrochozoan was inspired by the presence of a feeding structure called a lophophore and a type of larva called a trochophore. A lophophore is a specialized structure that rings the mouth and functions in suspension feeding (figure 33. 4a). Trocophores are a type of larvae common to several phyla of lophotrochozoa (figure 33. 4b). The primary contrast between lophotrochozoans and ecdysozoans involves the methods of growth used by organisms in each group. Ecdysozoans grow by molting shedding of the hard exoskeleton or soft cuticle (figure 33. 5). Protostomes have diverged into 22 different phyla that are recognized by distinctive body plans. All protostomes are triploblastic and bilaterally symmetric, and all protostomes undergo embryonic development in a similar way. The nature of the coelom varies among protostomes though (figure 33. 6).
