Which of the following describes a symbiotic relationship between two organisms in which one organism benefits and the other is harmed?
Correct Answer: C. Parasitism
Explanation
Mutualism, parasitism, and commensalism are all symbiotic relationships (close, long-term interactions between two species). Parasitism correctly describes a symbiotic relationship in which one organism benefits and another is harmed (for example, giardia is a parasite found in contaminated water that can live in human intestines and cause gastrointestinal distress). Mutualism describes a relationship in which both species benefit from the interaction. Competition describes an interspecies (or intraspecies) relationship in which two species (or two members of the same species) occupying the same habitat compete for resources and the fitness of one species is harmful to the other (for example, two male deer competing to establish a dominance hierarchy or an invasive plant species taking nutrients from a native species). Commensalism describes a relationship in which one organism benefits and another organism neither benefits nor is harmed (for example, a cattle egret eating insects as it follows grazing cattle). Divergent evolution is not an interspecies relationship but an evolutionary concept by which the accumulation of differences between groups can lead to the formation of new species, often due to species diffusion to different, isolated environments.
