Final answer:
The owl would receive approximately 4.5 units of energy from the mouse if the energy transfer efficiency is about 10% between trophic levels.
Step-by-step explanation:
If we assume the energy transfer between trophic levels is approximately 10% (which is a widely accepted average), then if a grasshopper contains 450 units of energy, the mouse would receive about 45 units after eating the grasshopper (10% of 450). Subsequently, when the owl eats the mouse, it would only receive around 4.5 units of energy from the mouse (10% of 45), assuming that there's no other energy loss and that the owl gets all the energy from the mouse's body. This principle is part of the 10% rule in ecological pyramids where each level only captures about 10% of the energy from the level below it.