Final answer:
Bryozoans have a central gastrovascular cavity as their gut, used for feeding the colony and excreting waste. They present in variable colony forms but have consistent cylindrical individual morphology with bilateral symmetry across different species.
Step-by-step explanation:
Bryozoans, which first appeared in the Ordovician period, have a gut that is part of a cylindrical morphology. Each individual bryozoan, known as a zooid, feeds the colony and excretes waste. The zooid is bilaterally symmetrical and often takes the form of an autozooid. These autozooids have a central gastrovascular cavity lined by the gastrodermis for digestion. The mouth of the bryozoan is situated at the oral end, enveloped by tentacles which facilitate in filter feeding. The overall structure of bryozoans can be highly variable, presenting in forms like branching structures or gelatinous blobs, as they typically live in colonies. These colonies are often encrusting surfaces and are a prominent part of many fossil assemblages.