Plants get energy from the sun and use carbon dioxide and water in the process called photosynthesis to produce energy in the form of sugars. Animals use sugars provided by plants and other organisms to produce energy in the form of adenosine triphosphate (ATP).
All living organisms get their matter and energy from the environment, whether it is from the air, soil, water or food. Scientists devised the Pyramid of Energy to explain how energy moves across the food chain. The pyramid contains producers, primary consumers, secondary consumers and tertiary consumers. Producers, such as plants, are at the bottom of the pyramid. Producers do not consume other organisms for energy. Primary consumers rely on plants for their energy and secondary consumers rely on primary consumers for their energy. At the top of the pyramid are tertiary consumers, or decomposers, which gain energy from secondary consumers. Decomposers break down decaying organisms to obtain their energy. Cells in living organisms require energy to maintain their structures and function, as well as to grow and reproduce. Living organisms also produce electrical energy and can make copies of DNA molecules by using ATP. Energy is also used to move muscles and carry signals from the brain to different nerves.