Without homeostasis, the internal and external environments of organisms would be unbalanced. Too much of one thing can harm, and even kill the organism. For instance, when dogs are hot, they pant because they don't have sweat glands to maintain homeostasis. However, if the dog could not pant, it would die from its high body temperature.
The amount of total energy at each trophic level decreases as it moves through, so 90% is lost at each level. This means that only 10 percent of the energy at any trophic level is transferred to the next level; and the rest is lost as heat.
In this case, if a plant ecosystem has 3000000 kilocalories (kcal) of energy, about 300000 kcal will be transferred to primary consumers (for example grass hoppers). If the red-tailed hawks are tertiary consumers, they will get 3000 kcal of energy.