What two types of digestive systems do invertebrates have?
slow or complete
fast or slow
unstable or complete
incomplete or complete
Invertebrates have one of two types of digestive system: an incomplete or complete digestive system. Both are shown in Figure below . An incomplete digestive system consists of a digestive cavity with one opening. The single opening serves as both mouth and anus. A complete digestive system consists of a digestive tract with two openings. One opening is the mouth. The other is the anus.