c) The body cavity evolved before the lophophore
Explanation:
The most widespread type of body cavity is a celoma, that is, a cavity filled with fluid that is completely lined with a thin layer of tissue that develops from the mesoderm. The rows whose members have a coelom are called coelomates.
Members of some rows have a body cavity that is not completely surrounded by tissue derived from the mesoderm. This type of cavity is known as pseudocelloma, and the rows whose members present it are collectively known as pseudocellomates. Roundworms (nematodes) are the largest group of pseudocellomats. Some rows of bilateral animals have no body cavity and are known as acelomados. For example, flat worms have no cavity between their intestine and the body wall; instead, the space is full of solid fabric.
Since the acellominated and pseudocellomized body planes appear to be more "primitive" than the plane of a celomated body, it was once thought that the acelomated and pseudocellomatic rows represented a distinctive lineage that initially diverged in animal evolutionary history, before the origin of the Celoma However, now the systematics recognize that the various rows of acelomados and pseudocellomados are not all closely related to each other, but form branches at various points in the evolutionary tree of animals. Thus the body planes of acelomados and pseudocellomados are not evolutionary precursors of celoma, but rather modifications of it.
Among the bilateral animal ranks, embryological development follows a variety of paths. However, these varied pathways can be grouped into two categories known as protostomes and deuterostoma development. In the development of a protostomes, the body cavity is formed within the space between the body wall and digestive quality. In the development of deuterostoma, the body cavity is formed as an excretion of the digestive cavity. The two types of development also differ in the pattern of cell division that begins immediately after fertilization and in the method by which the mouth and anus are formed. Protostomes and deuterostomes are branches are characteristic evolutionary branches within bilateral animals. Annelids, arthropods and mollusks have the development of protostomas, while echinoderms and chordates have deuterostomes.
The rows of protostomed animals are divided into two groups, which correspond to two different lineages that diverged early in the evolutionary history of the protostomes. One group, the ecdisozoans, includes a row like those of arthropods and roundworms, whose members have a special food structure called a lophophore, as well as some rows whose members go through a stage of development called a trochophora larva. Molluscs, annelids and flat worms are examples of the filum lophotrochozoans.
