Massachusetts Comprehensive Assessment System (MCAS) Biology Practice Test

What is the primary function of decomposers in an ecosystem?

1. They compete with consumers for energy

2. They convert nutrients back into the soil

3. They are the main producers of energy

4. They enhance the biodiversity of the ecosystem

The correct answer is: They convert nutrients back into the soil

Decomposers play a crucial role in ecosystems by breaking down dead organic matter, such as fallen leaves, dead animals, and other decomposing materials. This process not only helps to recycle nutrients but also returns essential elements like nitrogen and phosphorus back to the soil, making them available for use by plants. This nutrient cycling is fundamental for sustaining plant growth and, consequently, the entire food web that relies on those plants for energy. Without decomposers, ecosystems would become overloaded with waste and dead matter, leading to nutrient depletion and disruption of ecological balance. Thus, the primary function of decomposers is to convert nutrients back into the soil, supporting the health and stability of the ecosystem.