Final answer:
The main difference between a food chain and a food web is that a food chain shows a single pathway of energy flow, while a food web illustrates multiple pathways by representing all possible food chains within an ecosystem. So the correct option is A.
Step-by-step explanation:
A food chain and a food web both describe the energy transfer dynamics in an ecosystem. The difference between them lies in how they depict the feeding relationships and energy flow. A food chain shows a single pathway by which energy and matter flow through an ecosystem, representing a linear series of feeding interactions. In contrast, a food web displays multiple intersecting pathways, incorporating many food chains to illustrate a more complex and interrelated system, demonstrating that most organisms can eat and be eaten by more than one species.
- A food chain shows a single path of energy flow.
- A food web shows all the possible food chains and intersecting paths of energy flow within an ecosystem.
Hence, the correct answer to the question is A. A food chain shows only one path of energy flow, whereas a food web shows all the possible food chains in an ecosystem.