All animals need a digestive system to obtain nutrients and energy from food. Even simple animals like flatworms have a rudimentary gut, though it may be very different from the complex digestive systems of mammals or birds.
The word "gut" often refers to the digestive tract, which includes:
* Mouth: For ingestion.
* Esophagus: For transporting food to the stomach.
* Stomach: For breaking down food mechanically and chemically.
* Small intestine: For absorbing nutrients.
* Large intestine: For absorbing water and forming waste.
* Anus: For expelling waste.
Even animals that have evolved specialized ways of obtaining food, like parasites, still need a digestive system. For example, tapeworms have a very simple digestive system that allows them to absorb nutrients directly from the host's intestines.
In short, all animals, regardless of how simple or complex they are, need a digestive system to survive. This means that there are no animals with no guts.