Question

Why is there so much variety of bacteria in the mouth

Answer 1

There is a wide variety of bacteria in your mouth because it is dark, damp, and has a good source of nutrition. Also, when you breathe in, bacteria enters your mouth and can then reproduce.

Answer 2

The human mouth is full of bacteria because the mouth is a warm, wet environment, and these are perfect conditions for bacteria to reproduce. It's a perfect stable environment.