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  1.  Energy Loss in the Ecosystem (i) Solar radiation (ii) Energy Loss in the Biosphere (iii) Measure of primary production e.g. the amount and rate of energy fixation
  2. Laws of thermodynamics.


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?

Solar Energy: Only about 2% of solar energy is used by green plants while the rest is lost to the earth’s surface. Thus, energy is a limited factor in the production of autotrophs.

Energy Transformation in Nature

When primary consumers, 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 Laws: Energy transformations in nature are governed by the laws of thermodynamics.

The first law of thermodynamics 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 form of fuel changes into mechanical energy. So, energy can only be converted from one form to the other.

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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 Level

Pyramid of energy

  1. 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.
  2. 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.

Food Chain 

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

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