What does the term parasite refer to?

The term parasite specifically refers to an organism that lives on or within another organism, known as the host, and derives its nutrients and sustenance from that host. This interaction often adversely affects the host, as the parasite benefits at the host's expense. The relationship is characterized by the dependency of the parasite on the host for survival, growth, and reproduction. In many ecological contexts, understanding this relationship is vital, especially regarding pest management and biological control strategies in agriculture.

The other options pertain to different biological concepts and do not accurately reflect the definition of a parasite. An insect that benefits from symbiosis involves a mutually beneficial relationship, rather than one-sided exploitation. A plant that thrives in poor conditions doesn't relate to parasitism; it indicates resilience or adaptation. A genetically modified organism involves biotechnology and manipulation at a genetic level, which is unrelated to the definition of parasitism. Thus, the correct answer captures the essence of parasitic relationships accurately.