BIO153H5 Chapter Notes - Chapter 33: Symmetry In Biology, Lophotrochozoa, Protostome
Document Summary
There are two major groups of bilaterally symmetric, triploblastic, coelom animals: protostome and deuterostome. The protostome and deuterostome patterns of early development represent different pathways for building a bilaterally symmetric body with coelom. When gastrulation happens in protostomes, the initial pore that forms in the embryo becomes the mouth. If a coelom (body cavity) forms later on in development, it forms from openings that arise within the blocks of mesoderm tissue. Phylogenetic studies have supported the hypothesis that protostomes are a monophyletic group (the protostome development arose only once) Recent data indicates that there are two major subgroups within the protostomes : lophotrochozoa and ecdysozoa. Lophophore: a specialized structure that rings the mouth and functions in suspension feeding. Lophophore are found in bryozoans (moss animals), brachiopods (lamp shells), and phoronids (horseshoe worms) Trochophore: larva has a ring of cilia around its middle.
