Cellular respiration converts the energy of fuel molecules to a form of energy that a cell can use to perform work. in an average day, most adult humans need to consume about 2,000 calories to maintain their health. however, the exact amount of dietary calories a person needs depends upon many factors, including the person's age, physical activity, size, and health. foods that we consume vary greatly in their nutritional content and quality. a large hard-boiled egg, for example, has about 75 dietary calories and contains about 70% of our recommended daily intake of cholesterol. molecules that come from the food we eat provide energy for the amazing work that goes on inside of our cells. this energy, stored inside of our food, is a form of

Digestion because it removes waste

Hunting in the darksome fish rely on senses beyond sight. in the darkness of the marianas trench, a fish called the rattail has an extremely sensitive sense of smell. the fish uses scent, rather than sight, to steer toward food. once it's near food, the rattail uses a special organ on the bottom of its chin to guide itself by feel.marine snowone staple of the deep sea diet is "marine snow," flakes of organic, edible substances that sink down from the upper ocean. animals at the ocean's bottom find sustenance in everything from the bodies of dead creatures to fecal matter. marine snow is diverse enough to support numerous species. for instance, several species of snails and worms feed exclusively on deceased whales.microorganismsthe deep sea is an intricate ecosystem, and even the ocean floor itself plays a part. hydrothermal vents are cracks in the sea floor where erupting magma mixes with ocean water to produce plumes of hot, sulfur-rich chemicals. some microbes can use these chemicals for energy, sustaining their existence and that of the animals who depend on their roles in the deep sea food chain.