Massachusetts Comprehensive Assessment System (MCAS) Biology Practice Test

What process is facilitated by a composter in the decomposition of plant material?

1. Nitrogen is absorbed into the soil.

2. Carbon dioxide is released to the atmosphere.

3. Heat energy is generated to accelerate decay.

4. Oxygen is produced for other plants.

The correct answer is: Carbon dioxide is released to the atmosphere.

The correct answer highlights a significant aspect of the composting process. During decomposition, microorganisms break down organic material from plant matter, which leads to the release of carbon dioxide as a byproduct. This release occurs because microorganisms respire, using oxygen to break down the organic molecules and producing carbon dioxide as part of their metabolic processes. Composting involves an aerobic process, where these microorganisms utilize available oxygen to decompose organic waste, leading to an increase in carbon dioxide levels not just in the compost but as a release into the atmosphere. This natural cycle is vital for maintaining ecological balance, as it contributes to the global carbon cycle. Understanding the role of carbon dioxide in composting helps illustrate the dynamic interactions within ecosystems. This process does not primarily focus on nitrogen absorption, heat production, or oxygen generation; while those aspects may be associated with the decomposition process in certain ways, they do not directly encapsulate the primary outcome of what happens in a composter regarding the release of carbon dioxide.