Final answer:
The spreading of a disease among lily pads in a pond is an example of parasitism, where the disease benefits and the lily pads are harmed.
Step-by-step explanation:
The disease spreading among lily pads in a pond ecosystem is an example of parasitism. Parasitism is a symbiotic relationship where one organism, the parasite, benefits at the expense of another organism, the host, which is harmed. In this case, the disease-causing organism would be the parasite taking advantage of the lily pads, which serve as the host.
Key terms that are helpful for understanding this interaction include mutualism, where both species benefit; commensalism, where one species benefits and the other is unaffected; and competition, where species compete for the same resources. However, parasitism is distinct in that one party is negatively affected.