What type of body cavity does Mollusca have?
But molluscs have developed a true coelom, an internal body cavity enclosed by mesodermal membranes. The coelom in molluscs, however, is strangely reduced to a small space around the heart, sometimes called a hemocoel.
What type of body cavity do Cnidaria have?
Cnidarian bodies have two or sometimes three layers. A gastrovascular cavity (coelenteron) has a single exterior opening that serves as both mouth and anus. Often tentacles surround the opening.
What type of body cavity do sponges have?
Simple sponges of the asconoid type have a small central cavity or spongocoel, where the choanocytes are located. The more complex syconoid sponges (like Grantia) have folded canals of feeding cells off the spongocoel.
Do platyhelminthes have a body cavity?
Flatworms are bilaterally symmetrical with a defined head and tail region and a centralized nervous system containing a brain and nerve cords. They have no circulatory system or body cavity (coelom), but they do have an excretory and digestive system. They take in oxygen through their skin.
What is the digestive system of Mollusca?
Clams (and all mollusks) have a complete digestive system. It consists of a mouth where food is ingested, a short connecting tube called the esophogus, a stomach which temporarily holds food, and an intestine where food digestion and absorption takes place.
Are mollusk bodies segmented?
Evolution of Mollusks Mollusks are probably most closely related to organisms in the phylum Annelida, also known as segmented worms. Unlike segmented worms, however, mollusks do not have body segmentation. The basic mollusk body shape is usually quite different as well.
Do cnidarians have complete guts?
Cnidarians have an incomplete digestive tract, which means that they eat and excrete from the same opening. Chordates (like you) have a complete digestive tract, meaning that you eat and excrete from different openings.
What type of digestion occur in cnidarians?
Cnidarians carry out extracellular digestion, where enzymes break down the food particles and cells lining the gastrovascular cavity absorb the nutrients. Cnidarians have an incomplete digestive system with only one opening; the gastrovascular cavity serves as both a mouth and an anus.
What type of gut do porifera have?
Taxonomic level: phylum Porifera; grade of construction: cellular, with no distinct tissues or organs; symmetry: variable; type of gut: none; type of body cavity other than gut: none; segmentation: none; circulatory system: none; nervous system: none; excretion: diffusion from cell surface.
Do sponges have a stomach?
Internally, they do not have brains, stomachs, or other organs. This is because sponges evolved much earlier than other animals. In fact, sponges do not even have true tissues. Instead, their bodies are made up of specialized cells (cell-level organization) that do specific jobs.
What type of digestive system do platyhelminthes have?
Physiological Processes of Flatworms Most flatworms have an incomplete digestive system with an opening, the “mouth,” that is also used to expel digestive system wastes. Some species also have an anal opening. The gut may be a simple sac or highly branched.
Why are platyhelminthes more advanced than cnidarians?
Flatworms are more complex than cnidarians. Cnidarians have two layers of cells, the ectoderm and the endoderm; flatworms have a middle layer called the mesoderm between the other two layers (Fig. 3.16). The cells of the ectoderm and endoderm are also more organized than similar cells of cnidarians.