1: how might bacterial growth in a human body be similar to or different from bacterial growth on the
agar in a petri dish?

Bacterial growth in human body is different from bacterial growth on the agar in a petri dish.

Explanation:

We know that in the human body there is the immune system which will interrupt the bacterial growth as they will be recognized as a foreign body and will be destroyed by employing immunological pathways.

Whereas on the agar medium balanced nutrient, pH, salts, amino acids and optimum temperature is provided for the bacterial growth. The desired conditions would be favorable for the  growth of bacteria.