What Do All Living Things Need?
All living things require a source of energy, nutrients, water, space to grow and reproduce, and a relatively stable environment that allows homeostasis. Many organisms also require oxygen, but this is not a universal requirement, and oxygen is actually deadly to certain organisms. Indeed, beyond these basic categories of needs, the requirements of organisms vary vastly from species to species.
Living things all require energy, and they obtain that energy through one of three basic ways. The basis for almost all life is in photosynthesis, the use of energy in sunlight to create carbohydrates from oxygen and water. Thus, the sun is the basic source of energy for almost every organism. The only exception are certain specialist microbes that feed on inorganic chemicals near hydrothermal vents and similar extreme environments. These two categories are known as autotrophs or primary producers, and all other organisms gain their energy from feeding on them or on the organisms that eat them.