Question

Legumes, a type of plant, require Rhizobia, a type of soil bacteria, to survive since these organisms fix nitrogen. Rhizobia use the legumes for food. What would most likely happen to the legume population if Rhizobia suddenly became extinct?
become extinct
learn to fix nitrogen
benefit in the long run
stay the same

Answer 1

become extinct.

Explanation: Legumes depend on Rhizobia for biologically available nitrogen through a mutualistic symbiosis. If Rhizobia disappeared, most legumes would not obtain enough nitrogen to grow and reproduce and their populations would decline toward extinction (unless nitrogen were supplied some other way, which the question does not assume).