Final answer:
The correct answer is a. frog to hawk, as it demonstrates the flow of energy from a terrestrial to an aquatic ecosystem, with the frog being a terrestrial organism and the hawk potentially representing an aquatic predator.
Step-by-step explanation:
The question asks which pair of organisms represents the flow of energy from a terrestrial to an aquatic ecosystem. To address this question, we need to understand that energy transfers in ecosystems through food chains, where energy typically flows from plants to various levels of consumers. In terrestrial ecosystems, this might start with a grasshopper eating plants, and continue with a bird preying on the grasshopper. If we consider the transfer to an aquatic ecosystem, we need to identify an animal that might carry energy into a water-based system, like a frog that could be consumed by an aquatic predator like a fish.
Therefore, the correct answer is a. frog to hawk, assuming the hawk represents an aquatic system's predator that might prey on frogs which come from a terrestrial ecosystem. This connection signifies the energy transfer from land to water.
It is important to note that food chains depict the relationships between producers and consumers and demonstrate how energy decreases with each increase in trophic level. Trophic levels are the different levels within the food chain where organisms are grouped based on their feeding position.