The transformation of energy between the different components of an eco-system is known as ‘energy flow’.
This is very important, as it determines the density and diversity of organisms as well as their development and functional status. The energy flow in an eco-system is always unit-directional in nature.
To prepare food and to store it in the form of chemical energy, green plants, with the help of their green pigments known as ‘chlorophyll’, trap solar energy and convert carbon dioxide (C02) and water (H2O) into complex food materials with the help of other nutrients. This is done through the process of photosynthesis and is referred to as primary production.
When herbivores consume autotrophic plants as food, part of the food is assimilated and the rest is ingested.
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Some parts of the assimilated food, the potential energy stored as chemical energy of food, get oxidized through respiration, the carbon-carbon bonds are broken and carbon combines with oxygen to form carbon dioxide, releasing kinetic energy. Some parts of the energy are used by the organism to do work and the rest dissipates as heat.
Image Source: somas.stonybrook.edu/~frisk/Pictures/EMBgraphicOct2008.JPG
The efficiency of energy utilization varies from organism to organism and within similar organisms it varies with the physical structure of the organism and its age. The remaining part of the assimilated food (energy) is stored in somatic and reproductive tissues for growth and reproduction.
The production of organic matter by heterotrophic organisms is known as ‘ Secondary Production’.
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The total quantity of plant material ingested and stored (assimilated) in the body of heterotrophic organisms (herbivore) is known as ‘Gross Secondary Production’ and the remaining part of the assimilated food (energy) after metabolic processes (mainly respiration), is known as ‘Net Secondary Production’.
When herbivores are consumed by carnivores (secondary consumers), further degradation of energy occurs.
Similarly, when carnivores (secondary consumers) are consumed by top carnivores (tertiary consumers) again, energy is degraded further. Thus, at each level of the system there is degradation of energy.
The decomposers ultimately, get food and energy by decomposing the dead organisms of all the tropic levels.
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The energy flow through various components of eco-system can be depicted as below.