It is defined as the branch of biology which deals with the rate of production of biomass. It deals with all the trophic levels. It also deals with the whole of ecosystem. It includes the gross primary productivity, net primary productivity, community and secondary productivity. The highest productivity is seen in the coral reef. This is followed by the tropical rain forest and sugar fields. The desert has the lowest productivity. The gross primary productivity is defined as the branch of biology which deals with the rate of organic matter synthesis by the producers in per unit time and area. The net primary productivity is defined as the branch of biology which deals with the rate of organic matter stored by the producers in per unit time and area. It is equal to the gross primary productivity minus the loss due to the process of respiration. The community productivity is defined as the branch of biology which deals with the rate of net manufacture of organic matter by the community in per unit time and area. The secondary productivity is defined as the branch of biology which deals with the rate of increase in the energy rich biomass by heterotrophs in per unit time and area.