An incomplete digestive system has only one opening. The food goes in the same opening that the waste comes out. It would be as if your anus was the same opening as your mouth! Although this sounds gross, some animals make it work. Animals with this digestive system evolved early in time and are considered pretty primitive. They don't have the fancy digestive system or other organs that we have.
EXAMPLES
➡️complete digestive system:
•examples
aschelminthes,
annelida,
arthropoda,
mollusca,
echinodermata,
hemichordata,
chordata.
➡️incomplete digestive system
•examples
Coelenterates,
Ctenophores,
Platyhelminthes.
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