Producers use solar energy (photosynthesis) to create food in the form of energy-rich molecules such as carbohydrates. This process, the synthesis of carbon dioxide into organic compounds, is called primary production and is indirectly or directly connected to the survival of all life on Earth.

Solar energy is converted into chemical energy by the producers, which then flows through the food chains.

During cellular respiration, glucose produced during photosynthesis is oxidised, releasing large amounts of energy. This energy is used by the organism for activities such as movement and reproduction. Heat energy is also released via respiration, which is circulated around the body by blood, keeping the organism warm.

This results in a loss of energy in the food chain as more energy is used by the organism than gained by its predator when consumed. These processes result in the loss of around 90% of energy when moving up each trophic level within food chains.