Energy Loss in the Ecosystem
You remember that energy exists in various forms, and various forms are interconvertible and as such one form of energy can be transformed into one another form. In nature, energy transformations are brought about by living organisms. Their activities cause energy to flow through ecosystems unidirectionally. Now, how does energy get lost in the ecosystem?
Energy Transformation in Nature
When primary consumer, the herbivores feed on the producers, the green plants, the secondary consumers, the carnivores in turn feed on the herbivores; the energy transferring efficiency in each stage is about 5-20% while the rest is lost to the atmosphere.
Energy transformations in nature are governed by the laws of thermodynamics.
The First Law of Thermodynamics
This states that when one form of energy is converted into another, the total quantity of energy is constant (there is no net loss or gain in energy) that is to say that energy is neither created nor destroyed. Hence, in the process of burning, chemical energy of wood changes into heat and light. In a motor vehicle, energy in the form of fuel changes into mechanical energy. So, energy can only be converted from one form to the other.
Second Law Of Thermodynamics
The law states that when one form of energy is converted into another, a proportion of it is converted into heat. The second law of thermodynamics is sometimes known as the entropy law; entropy being a measure of disorder in terms of unavailable energy in a closed thermodynamic system.
How the Laws are Used to Explain Energy Flow Across the Trophic Levels
Pyramid of Energy
- According to the first law, energy is transferred into a variety of other forms in the successive trophic level but the sum total is constant.
- Using the second law, we observe that during energy transformation in the successive trophic levels, a proportion of it is converted into heat which is lost, hence the progressive drop in energy in successive trophic levels and also the pyramidal shape of feeding relationship.
- In accordance with first law, chemical energy stored in plants, can be converted into light energy in glow-worm which in turn is converted into electrical energy in fire-fly and when eaten by man, it is converted into mechanical energy in muscular contraction without any loss or gain.
- The second law shows that when energy flows through a food chain, only a small proportion of the energy taken up by each link is transferred to the next step. This is because at each transfer, most of the energy is lost as heat.
According to the second law:
- In the flow of energy from herbivore to carnivore, there is loss of usable energy. This loss of energy means that les life can be maintained at highest trophic level.
- The energy travels from one organism to another with a loss of energy each time it enters another organism. The various organisms represent trophic levels or stages of energy flow.