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

Answer 1

become extinct.

Reason: Legumes depend on Rhizobia for biologically fixed nitrogen. They cannot “learn” to fix nitrogen — nitrogen fixation is a complex metabolic capability encoded in genes and would require long-term evolution or new symbioses. Without Rhizobia (or some immediate alternative nitrogen source), most legumes would suffer severe nitrogen starvation, reduced growth and reproduction, and populations would decline sharply or locally go extinct.