As energy travels up the food pyramid, it is lost primarily in the following ways:
- Heat - A significant amount of energy is lost as heat at each trophic level due to metabolic processes.
- Excrement/feces - Organisms lose energy through waste products that are not digested or absorbed.
- Indigestible food - Energy is also lost through parts of the food that are not digestible.
Air is not typically considered a direct means of energy loss in this context, so the correct selections would be 2, 3, and 4.