BIO153H5 Chapter Notes - Chapter 33: Bivalvia, Annelid, Synapomorphy
Document Summary
As a group, protostomes live in about every habitat that you might explore. They also include two of the most important model organisms in all of biological science: the fruit fly drosophila melanogaster and the roundworm caenorhabditis elegans. When gastrulation occurs in protostomes, the initial pore that forms in the embryo becomes the mouth. If a coelom (a body cavity) forms later in development, it forms from openings that arise within blocka of mesodermal tissue. Phylogenetic studies have long supported the hypothesis that protostomes are a monophyletic group, meaning the protostome deveopmental sequence arose just once. The two monophyletic groups of protostomes are called the lophotrochozoa and the ecdysozoa. The 13 phyla of lophotrochozoans include the mollusks, annelids, and flatworms. A lophophore is a specialized structure that rings the mouth and functions in suspension feeding. They are found in bryozoans (moss animals), brachipods (lamp shells), and phoronids (horshoe worms).
