one
yes, planarians have one opening in their digestive system
Jellyfish have a simple digestive system. They have a digestive cavity with cells lining the wall that carry out the digestive function.
A gastrovascular cavity is a digestive sac with only a single opening. A complete digestive tract (otherwise known as an Alimentary canal) has two openings (a mouth and anus) between its digestive tubes unlike the gastrovascular cavity in which food is ingested and eliminated through the same opening (example would be hydra)
A digestive sac not related to other endomembrane structures
The stomach
Yes
has only a single openning
The stomach
jellyfish
No.
Jellyfish have a body type that is like a sac. They eat with their large stomach sacs, which are called coelenterons.