Final answer:
Annelids, arthropods, echinoderms, and nematodes all possess some form of a body cavity, with Annelida, Arthropoda, and Echinodermata having true coeloms or hemocoels, while Nematoda has a pseudocoelom. Porifera and Cnidaria, however, do not have a body cavity.
Step-by-step explanation:
Within the study of zoology, a body cavity, also known as a coelom, is a fluid-filled space separating the digestive tract from the outer body wall. This structure is present in various animal phyla and is important for several functions, including the distribution of nutrients and the placement of internal organs.
Here's a brief overview of the presence of body cavities in the phyla mentioned:
- Phylum Annelida: Annelids do have a body cavity, a true coelom that is segmented and lined with tissue derived from mesoderm.
- Phylum Arthropoda: Arthropods have a hemocoel, which is a primary body cavity. Although not a true coelom, a hemocoel still functions in a similar manner, housing the internal organs and allowing for the circulation of hemolymph.
- Phylum Echinodermata: Echinoderms possess a true coelom. They have a unique water vascular system, part of which functions as a hydrostatic skeleton.
- Phylum Nematoda: Nematodes, or roundworms, have a pseudocoelom, which is a body cavity not entirely lined by mesodermal tissue. This pseudocoelom still serves as a space for the organs and can act as a hydrostatic skeleton.
- Phylum Porifera: Sponges, belonging to Phylum Porifera, do not have a body cavity. They have a simple body plan without true tissues and organs.
- Phylum Cnidaria: Like Porifera, Cnidarians, which include jellyfish and corals, also lack a body cavity. They have a body plan comprising only two main layers and a gastrovascular cavity for digestion.