Final answer:
An incomplete gut or gastrovascular cavity is a type of digestive system found in organisms such as flatworms, comb jellies, and cnidarians. This system involves extracellular digestion, with food being taken into the cavity through a single opening. Cnidarians have specializations for feeding, including cnidocytes and tentacles.
Step-by-step explanation:
An incomplete gut or gastrovascular cavity is a type of digestive system found in organisms such as flatworms, comb jellies, and cnidarians. In this system, food is taken into the cavity through a single opening, which serves as both the mouth and the anus. Enzymes are secreted into the cavity, and the cells lining the cavity absorb the nutrients. This type of digestion is extracellular, as enzymes are released into the cavity to break down the food particles.
Specializations for feeding in cnidarians include cnidocytes (stinging cells) and tentacles. Cnidocytes are specialized cells that contain nematocysts, which are used to capture prey or defend against predators. Tentacles are elongated extensions that surround the mouth and are equipped with cnidocytes. These adaptations assist in the capture and ingestion of food.