Energy and nutrient transfer
Organisms need food for energy to move, keep warm etc
Organisms need food for growth: food provides the proteins, fats and carbohydrates- the raw materials needed to build new cells
Biomass is the weight of a organism as it builds new cells and tissues
The source of energy for all living things is the sunlight
Each step in a food chain is called a trophic level
Biomass is lost in faeces because not everything consumed can be digested
The amounts of energy and biomass contained in living organisms always decreases at a stage of a food chain because biomass is lost as waste products and is used to produce energy. This energy is used in movement, in controlling the body temp and in growth etc.