Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

Which of the following is a correct association between a cycle and its process?

1. Nitrogen Cycle - Plants use nitrogen directly from the atmosphere

2. Phosphorus Cycle - Involves decomposition and returns to soil

3. Carbon Cycle - Animals contribute carbon by fixing glucose

4. Water Cycle - Rain cannot be absorbed by soil

The correct answer is: Phosphorus Cycle - Involves decomposition and returns to soil

The association between the Phosphorus Cycle and the process of decomposition returning nutrients to the soil is correct because the phosphorus cycle involves the movement of phosphorus through the lithosphere, hydrosphere, and biosphere. During decomposition, organic matter, including dead plants and animals, breaks down, releasing phosphorus back into the soil. This phosphorus is then available for uptake by plants, continuing the cycle. It highlights the essential role of decomposition in making nutrients accessible in ecosystems. In contrast, the other associations present inaccuracies or misunderstandings about the cycles. For instance, in the nitrogen cycle, plants cannot use atmospheric nitrogen directly; they rely on specialized bacteria to convert nitrogen into a form they can absorb. In the carbon cycle, animals do not fix glucose; instead, plants perform photosynthesis to convert carbon dioxide into glucose, while animals contribute to the carbon cycle primarily through respiration and decomposition. Lastly, in the water cycle, rain is typically absorbed by soil, promoting groundwater replenishment and plant growth.