Which of the following best describes the key components of an ecosystem?

• A. Living organisms only
• B. Physical environment only
• C. Living organisms, physical environment, and interactions
• D. Energy flow and food webs

Answer: (C)

Ecosystems include living organisms, the nonliving surroundings, and the connections between them. This combination matters because energy flows through the living things, nutrients cycle through both biotic and abiotic parts, and the various relationships—such as predation, decomposition, and symbiotic ties—shape how the system functions. The option that mentions all three components—living organisms, the physical environment, and their interactions—best captures what an ecosystem truly is. Choices that focus only on living things or only on the environment miss important pieces of how ecosystems operate, and energy flow and food webs describe a part of the interactions without naming the environment or all living components. For example, in a pond, fish and aquatic plants are the living parts; the water, temperature, and minerals are the nonliving parts; and interactions like feeding, decay, and nutrient cycling connect everything together.