What term describes a symbiotic relationship in which two different species both benefit?

• A. Mutualism
• B. Commensalism
• C. Parasitism
• D. Predation

Answer: (A)

When two different species both gain something that helps them survive or reproduce, that relationship is mutualism. This is the hallmark: a win-win in which each partner provides something the other needs—like a bee getting nectar from a flower while helping the flower by transferring pollen, or certain gut microbes helping an animal digest food while receiving a warm, nutrient-rich environment in return. Other familiar examples include algae living inside corals, where the algae share energy from photosynthesis and the coral provides a protected place and nutrients.

Why this fits the description best here: the term describes a true two-way benefit. In other kinds of relationships, the benefits aren’t shared equally or aren’t mutual. Commensalism means one species benefits and the other is largely unaffected. Parasitism means the parasite benefits at the host’s expense. Predation describes one organism eating another, which benefits the eater but harms the prey.