Final answer:
Opportunistic pathogens can originate from animals, plants, soil, and water. These pathogens become problematic when the host's immune system or protective barriers are compromised.
Step-by-step explanation:
Opportunistic pathogens can originate from various sources including animals, plants, soil, and water. These pathogens typically do not cause disease in healthy individuals, but can become problematic when the host's immune system or protective barriers are compromised. For example, opportunistic pathogens can cause infections in individuals with weakened immune systems, recovering from surgery, or with a breach in protective barriers such as severe wounds or burns.