Whats the most complex organism with a bi-directional digestive system? Are there any?
The least complex multicellular organisms tend to have tidal guts. That is, the food comes in and the waste products go out, the same place. Unidirectional guts evolved for animals to be able to store food, and to allow animals to eat more complex foods, that take longer to digest. I don’t know of any “bi-directional” guts, except that most animals can vomit the contents of their stomachs in some circumstances.
