Massachusetts Comprehensive Assessment System (MCAS) Biology Practice Test

What characteristic is unique to a mutualistic relationship?

1. Only one organism benefits

2. Both organisms are harmed

3. Both organisms benefit from the interaction

4. Neither organism is affected

The correct answer is: Both organisms benefit from the interaction

In a mutualistic relationship, both organisms involved derive benefits from their interaction, which is a defining characteristic of this type of symbiosis. This relationship showcases the cooperation between species, where both may gain resources such as nutrients or protection. For example, in a mutualistic partnership between bees and flowering plants, bees obtain nectar while assisting in pollination, which is vital for the plants' reproduction. The other options describe different types of relationships. When only one organism benefits, it describes a parasitic or commensal relationship where the other organism may not necessarily gain an advantage or may be harmed. In cases where both organisms are harmed, a competitive or antagonistic interaction is taking place, indicating a struggle for resources. If neither organism is significantly affected, it resembles a neutral interaction, which singularly lacks the mutual benefit characteristic that defines mutualism. Therefore, the key trait of mutualism is that both organisms reap benefits from their interaction.