The two basic laws that govern energy transformation in nature are the first and second laws of thermodynamics. The first law states that energy is neither created nor destroyed but may be transformed from one type into another. When solar energy strikes the roof of a building, part of its light energy is converted into heat energy. This law means that energy that enters the earth’s surface as light is balanced by that which leaves the earth surface as invisible heat radiation. The relationships between autotrophs and heterotrophs are controlled by the same basic laws which govern non-living systems. For instance, every year, solar radiations from the sun pass through the atmosphere and strike the forests, grasslands, lakes, oceans, cultivated fields, deserts and many other ecosystems. When light is absorbed and the objects become warmer, the light energy has been transformed into heat energy. The chlorophyll of the autotrophs converts part of this energy into chemical energy in the food it manufactures. The latter can be converted into a variety of other forms of energy.
In the muscle, chemical energy is transformed into mechanical energy (kinetic, during contraction and potential, during rest). In luminescent organisms (fire flies), chemical energy is converted into light energy. In electric fishes, chemical energy is converted into electric energy and so on. In all, no energy is actually created or lost, only inter conversions have taken place.
The second law states that energy transformation is not completely efficient, a proportion of it must escape as heat energy.
Furthermore, it states that when one form of energy is converted into another, a proportion is lost as heat energy. We have earlier discussed that energy transformation is not 100% efficient and that only a small proportion of the total energy reaches the final consumers. Only about 10.0% of the energy an organism takes is stored in its tissues. The rest is dissipated as heat, part is used up in the direction of food, respiration and capture of prey.
The second law of thermodynamics is sometimes known as the entropy law, being a measure of disorder in terms of amount of unavailable energy in a closed thermodynamic system. In an ecosystem, each time heat is lost from a food chain, highly complex organised food molecules are broken, i.e., disorganised, hence, an increase in the entropy as chemical energy (food) moves from the lower to the next high level.