Digestive bacteria and humans - Human beings have what is often called "good" bacteria in their digestive systems. This "good" bacteria exists in order to help the human to digest food
Some foods cannot be digested entirely: so, when these foods are consumed, the bacteria
in the digestive system feed on those foods.
The bacteria stay alive.
The human gets help with the process of digestion.
predation
mutualism
competition
commensalism

commensalism

Explanation:

Gut bacteria in particular are very important for digestion in humans and other species. ... In return, the bacteria get a steady supply of food. Commensalism: In commensalism, one organism benefits while the other organism neither benefits nor suffers from the interaction.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.