The transfer of food energy from the producers, through the series of organisms (herbivores to carnivores to decomposers) with repeated eating and being eaten is called food chain.
In Nature, we generally distribute into two groups. They are given below:
This type of food chain starts from the living green plants goes to grazing herbivores (that feed on living plants materials with their predator) and on to carnivores. An ecosystem with such type of food chain is directly dependent on the influx of solar radiation. Examples:
phytoplanktons→ zooplanktons→ fish.
grass→ rabbit→ fox sequence etc. are the example of a grazing food chain.
This type of food chain goes from dead organic matter into micro-organisms and then to organism feeding on detritus and their predators. Such system is thus less dependent on direct solar energy. They depend chiefly on the influx of organic matter produced in another system. Examples: a fallen leaf in the pond (affected by saprophytes, fungi, bacteria, protozoa etc.) and colonized mainly by phytoplanktons and benthic algae) are eaten and re-eaten by the key group of small animals. These animals include microbes, insect larvae, nematodes, bivalve, molluscans etc. The animals are detritus consumers.
Just as energy enters the detritus food chain from the grazing food chain as leaf litter or dead organism, energy can re-enter the grazing food chain from detritus food chain if organisms from later are consumed by grazers. Many of the organisms from the detritus food chain serve as prey for carnivores in the grazing food chain. In addition, many insects (beetles, Flies) spend their larval period in the detritus food chain and their adulthood in the grazing food chain. But the energy passed through eating from detritus to grazing food chain is very low in comparison to the energy from grazing to detritus food chain.
As a general model for the direction and extent of energy flow within a community, the food chain is very useful. It demonstrates the amount of energy found at any trophic level, the transfer of energy from one trophic level to the next and the amount of energy lost from the grazing food chain either through respiration or decay perhaps the most useful way to think of a food chain is a history of the fate of particular atoms. Food chain is a valid scientific record of what happens to the individual atoms.
Food chain is a natural condition never operate as isolated sequence but are interconnected with each other forming some sort of interlocking patterns, which is referred as a food web. Under natural condition,the linear arrangement of food chain hardly occur and these remains indeed interconnected with each other through different types of organisms of different trophic levels.
A balance system is essential for the survival of all living organisms of the system. For instance, the primary consumer not being in nature, the producers could have perished due to overcrowding and competition.
Similarly, the survival of primary consumer is linked with secondary consumers and so on. Thus each species of an ecosystem is indeed kept under some sorts of the natural check so that system may remain balanced.
The transfer of food energy from the producers through a series of organisms (herbivores to carnivores to decomposers) with repeated eating and being eaten is known as food chain. Producers utilize the radiant energy of sun which is transformed to chemical form (ATP) during photosynthesis. Thus green plants occupy the first trophic level in any food chain and are called primary producer level. The energy is stored in food matter manufactured by green plants which are then utilized by plants eaters, herbivores which constitute the second trophic level and are called the primary consumers(herbivores).Again, herbivores are eaten by the carnivores, which constitute the third trophic level i.e. secondary consumers (carnivores). These may be eaten still by other carnivores at tertiary consumers level i.e. by the tertiary consumers and finally, they are eaten by the top consumers. Examples: hawk, lion, tiger are the top carnivores. Some organisms are omnivores, eating the producers as well as carnivores at their lower level in the food chain. Such organism thus may occupy more than one trophic level in the food chain.
As we know that there are two types of food chain i.e. a) Grazing Food chain and b) Detritus food chain.
From above mention facts, we all are clear that food chain is the transfer of food energy from one level to another level or one organism to another organism. During the transfer of food energy, more amount of energy is degraded or loose in the form of heat. For example; green plants which absorb only a few part of sunlight to maintain their food. So they occupy the first trophic level i.e. producer level. These producers are eaten by other primary consumers. During energy flow from producer to herbivores, some amount of energy is degraded or loss in the form of heat. When these primary consumers are eaten by secondary consumers which occupy third trophic level, again there is corresponding more loss of energy.
If the energy in an ecosystem only between first trophic level to second trophic level, there may not be a large amount of loss of energy in the form of heat. For example; an ecosystem of grassland, if there are only vegetation and grasshopper, green vegetation utilize radiant energy and manufacture their own food which occupies first trophic level. This green vegetation is eaten by grasshopper which occupies second trophic level. Here only two trophic level are found so few amount of energy is degraded or loss in the form of heat.
That’s why we can say that shorter the food chain, greater will be the available food energy in an ecosystem.
E.p., Odum. Fundamentals of Ecology. USA: W.B Saunters Company, n.d.
Jr., Miller G.T. Living in the Environment. Belmont, California,USA: Wadsworth Publishing Company, 2003.