Hydra: extra and intracellular digestion
Each animal species has a way of digesting its food to get the nutrients needed for body maintenance and functioning. Most species digest inside their body through the digestive system, which consists of organs. However, there are some animal species that can digest food on the outside of the body.
1 - Intracellular Digestion
It is the one that occurs inside the cells. The process of digestion is done by lysosomes, through the action of digestive enzymes. Protozoa and porifers are examples of living beings that have this type of digestion.
2 - Extracellular Digestion
It is one in which the digestion process occurs entirely in the digestive system of the animal. We humans have this kind of digestion. Organs such as the stomach, liver and intestine act in this process. We can cite as examples, of beings that have this type of digestion, the animal species that are part of mammals, reptiles, birds, fish and amphibians. Invertebrate animals, such as the earthworm, also perform the digestive process extracellularly.
3 - Extra and intracellular digestion
There are some animal species, which the digestion process begins at the initial part of the digestion tube and completes inside the cells.
The animals that have this type of digestion are: hydras, planarians and mussels (mollusc species).
4 - Extra corporeal digestion
It is a type of digestion that occurs outside the animal's body. We can cite as an example, an animal species that has this digestive process, the spider. After killing its prey, it injects digestive juice into the dead animal's body. This juice digestes and, after this process, the spider eats the already digested food.