Massachusetts Comprehensive Assessment System (MCAS) Biology Practice Test

In a mutualistic relationship, what happens to the organisms involved?

1. Only one benefits

2. Both organisms benefit

3. Both organisms are harmed

4. Neither organism is affected

The correct answer is: Both organisms benefit

In a mutualistic relationship, both organisms benefit from their interaction. This type of symbiosis is characterized by the positive effects each organism has on the other, enhancing their chances for survival and reproduction. For example, bees and flowering plants exhibit mutualism; bees pollinate the flowers while obtaining nectar as food. This interaction increases the reproductive success of the plants and provides nourishment for the bees. In contrast, scenarios where only one organism benefits do not qualify as mutualism, as they describe parasitism or commensalism instead. Additionally, relationships where both organisms are harmed do not support the mutualistic definition, nor do those in which neither organism is affected, as these suggest a lack of interaction. Thus, the essence of mutualism lies in the reciprocal advantages gained by both parties involved.