In this article we will discuss about the energy source and ecological imbalance.
Source of Energy:
As referred to, sun is the only source of energy to our planet earth. The solar energy is released in form of invisible ultra-violet light and infra-red light, and visible light. Most of the ultra-violet light is absorbed by ozone layer in the upper atmosphere and most of the infra-red light having longer wavelengths are absorbed by atmospheric gases and some are reflected back in the environment.
Visible light constitutes nearly 50 per cent of solar energy; a part of it is reflected by clouds and dust particles, and a part is absorbed by the atmosphere (Fig. 12.19). In fact, sun radiates energy of nearly 1026 Joules/second but the earth gets only a fraction of it.
On the top of the atmosphere, the earth receives energy equal to 173 x 1015 Joules/second; of this about one-third is reflected back into the space by the atmosphere.
However, whatever amount of energy from the sun rEcology, eaches the earth in form of light and heat regulates the climatic phenomena on this planet. The green plants trap only a very small fraction (nearly one per cent) of available solar energy during the process of photosynthesis. Green plants trap light energy with the help of the pigment chlorophyll and convert it in chemical energy.
Thus, the energy trapped by green plants, i.e., autotrophs is utilised then in synthesizing organic compounds during the process of photosynthesis. The green plants, thus, are the only organisms which can trap and fix solar energy and can manufacture food used by them as well as by other organisms; hence, these are called producers.
The rate at which organic compounds are synthesized in a green plant or a population of green plants is called gross primary productivity (GPP). GPP gives us an idea of the proportion of assimilation of light energy into living matter of the plant. The organic compounds synthesized by plants are used as a source of energy for their body building, storage and various catabolic activities.
The total stored energy in form of organic matter (which is not used by the producer itself) is called net primary productivity (NPP). Exactly in the manner as a single plant contributes to the gross primary productivity and net primary productivity, all autotrophs in a community contribute to community productivity.
It has been mentioned earlier that all heterotrophs depend upon autotrophs (producers) directly or indirectly for food. So, by consuming autotrophs, heterotrophs consume organic matter from them. Energy, thus, enters the ecosystem through photosynthesis and passes through the different trophic levels. In other words, flow of energy takes place from the sun to autotrophs to heterotrophs.
The food consumed by heterotrophs is utilized in their maintenance and for storage too. If there is more storage than consumption, the biomass of the population would be higher at the end of a time period than at the beginning. So, this rate of increase in the biomass of heterotrophs is referred to as secondary productivity.
There occurs a continuous loss of energy all along the path when it is transferred from producer to a consumer and from consumer to the next consumer at the higher trophic level. For this, Lindemann (1942) formulated a concept called 10 per cent law.
To explain, when plants (producers) are eaten by a herbivore (primary consumer), about 10 per cent of energy in the food is fixed in herbivore’s body and when a carnivore (secondary consumer) eats up the herbivore, only about 10 per cent of energy in food is fixed in carnivore’s body.
Therefore, the second level consumer gain in energy is only 0.01 per cent of the net productivity of a plant (producer). This clearly shows that there is a loss of energy at each trophic level. So, the longer the food chain, the minimum is the energy available to the last member of the chain. It is, therefore, there are usually four or five steps in natural food chains.
The flow of energy is, however, unidirectional.
Ecological studies suggest that there exists an ecological balance between various constituents of abiotic and biotic components in the biosphere. For example, the various biogeochemical cycles operate in nature without any interruption and the abiotic as well as biotic components including producers, consumers and decomposers are significant.
If producers be destroyed carbon from atmospheric carbon dioxide cannot move to organic compounds in living organism and if consumers and decomposers be destroyed the organic compounds will accumulate resulting into locking up of carbon and further not available for cycling.
However, when all organisms of an area are studied, it becomes evident that in spite of different types of competitions and struggles between them, they co-operate each other on many ways or they seem to be interdependent. This dependence is called ecological balance. It is very necessary for the continuity of ecosystems and, hence, the biosphere.
However, man being a dominant organism of most ecosystems controls and modifies environment more extensively than any other organism. In fact, there have been significant changes in the natural environments due to man’s intervention and his rapid progress in colonization, urbanization, industrialization, agriculture, transportation and technology.
Thus, deforestation has provided land for agriculture and rural inhabitation, rural land has been converted into urban settlements and open spaces are fast vanishing.
All these have resulted into a mass-scale destruction of flora and fauna which has become detrimental to ecological balance. If, this balance is disturbed for long, it is bound to create a number of crises to the biological world including our lives. Hence, considering this importance, a number of ways are being adopted by government and private agencies so that ecological balance could be maintained.