All organisms require an energy supply for cellular activities such as protein synthesis and cell division, which enables organisms to grow.
Some of this energy is stored in the new material (for example, cellulose and muscle protein) made by growing organisms. This is called biomassThe mass of living material..
Organisms release energy from their food by the process of respirationThe chemical change that takes place inside living cells, which uses glucose and oxygen to release the energy that organisms need to live. Carbon dioxide is a by-product of respiration..
In most ecosystems on the planet the ultimate source of energy is the sun.