[SOLVED] Energy powers the body

Energy powers the body. If we break up the body, we see that there are numerous systems/organs that require energy to work. Although the body incorporates each of these organ systems simultaneously to carry out functions, and live, which of organ systems do you find most interesting and why? Also, in your opinion, which do you think is most important?
The human body is designed to be as efficient as possible, even when ambulating. Specifically, when examining gait, oftentimes, the average individual takes walking for granted; when was the last time you thought about walking (moving one leg in front of the other, pushing off the ground, landing on your heel, etc.)? As a comparative analysis, which animal’s method of locomotion do you find the most interesting? Please tell us what animal you choose and why.