Excretion is the removal of toxic materials, the waste products of metabolism and substance in excess of requirements from organisms. Metabolism is chemical reactions taking place inside cells, including respiration.
The body excretes three main waste materials. These are Carbon Dioxide, Urea and Water. Excretion is a very important feature to us because without it toxic substances will build up in our bodies and kill us. It also helps in maintaining the composition of body fluids.