Some prokaryotes live in animal digestive systems. what are three ways these prokaryotes are to the animals they live inside?

Prokaryotes that live in animal digestive systems are known as gut flora. The functions of the gut microbiota:
1. Inhibition of pathogens-Microorganisms within the gut flora use of all available nutrients and thus inhibit unwelcome pathogens that would compete for nutrients with it. Also, they secrete compounds that kill pathogens.
2. Protection and immune system- It have been shown that some bacterial species from the gut flora are able to drive the immune system to create cytokines.
3. Metabolism-Thanks to microbes from the gut flora, humans can digest some of the undigested carbohydrates it consumes, (microbes have enzymes that human cells lack for breaking down certain polysaccharides).

They must use the scientific method