In a food web, energy is transferred from one trophic level to the next, with plants (producers) having the most energy since they create their own energy through photosynthesis. As you move up the food chain, energy decreases due to energy loss at each trophic level (through processes like respiration and heat loss).
In this case, the order from most energy to least energy is:
- Grass (plants)
- Mouse
- Rabbit
- Owl
So, the population of organisms with the most energy in the path described (plants, mouse, rabbit, owl) is grass.