Air is a combination of gases used differently by many organisms. Carbon dioxide and oxygen make up two key components of air. Plants use the carbon dioxide in air to create sugars and oxygen. The oxygen created by plants ensures that many other living organisms, including humans, have oxygen to breathe. Oxygen is required in the human body to create ATP, a molecule needed to provide energy to living organisms.
The amount needed varies, but all living organisms require water. Some organisms live in water, some need salt water and others can only survive with fresh water. Plants take water to grow and create food. Certain plants, including algae, can only survive submerged in water, and they absorb carbon dioxide. For humans and animals, water serves as a digestion assistant, as well as a critical component of body fluids.
All living organisms need a source of nutrients. Nutrients, or food, can include fats, carbohydrates and proteins that are needed to maintain health and growth. Plants take in nutrients from the soil or the surrounding environment. This food allows the plant to carry out its processes. Humans and animals eat a variety of foods filled with nutrients. Because the body can store nutrients, humans can survive several days without food, but eventually the body's nutrient levels need replenishment.
Sunlight provides multiple uses to all living organisms. First, the sun serves as a heat source that warms the environment. The main necessity for sunlight stems from a plant's requirement for building food. Plants take in energy from the sun and use it to maintain growth and develop food and oxygen. Animals and humans indirectly need sunlight as a result, as they are heavily dependent on the functions of plants for food and oxygen. Sunlight also provides humans with vitamin D, a vitamin that ensures bone strength.
While habitats vary greatly from organism to organism, every living thing needs an efficient living space in order to survive. A key component of such a habitat is the proper temperature. Some plants can only survive in the dampest of conditions, while others require a drier home. The habitat must also have sufficient resources for the living organism. Limited resources will result in competition, leading to the death of certain organisms.