Which of the following best illustrates a transition from the biosphere to the geosphere?

• A. A bird migrating between continents
• B. Clouds forming from evaporated water
• C. A river eroding rocks to form a canyon
• D. A fallen tree decomposing and becoming part of the soil

Answer: (D)

Verified step by step guidance

1. Understand the key terms: The biosphere refers to all living organisms on Earth, while the geosphere refers to the solid parts of Earth, such as rocks, soil, and sediments. The question asks for an example of a transition from the biosphere (living organisms) to the geosphere (non-living Earth components).
2. Analyze the options: Each option represents a different interaction between Earth's systems. For example, a bird migrating involves movement within the biosphere, clouds forming involves the atmosphere and hydrosphere, and a river eroding rocks involves the hydrosphere and geosphere.
3. Focus on the correct answer: A fallen tree decomposing and becoming part of the soil represents a clear transition from the biosphere to the geosphere. The tree, once a living organism, decomposes and contributes organic material to the soil, which is part of the geosphere.
4. Consider the decomposition process: Decomposition is carried out by decomposers like fungi and bacteria, which break down the organic matter of the tree into simpler compounds. These compounds enrich the soil, integrating the tree's remains into the geosphere.
5. Conclude the reasoning: This example illustrates the interaction between Earth's systems, where the biosphere (living tree) transitions into the geosphere (soil) through natural processes like decomposition.