Energy Input in Ecosystem
Survival and functioning of ecosystem is dependent on the input of energy. Continuous availability of energy is essential for supporting diverse ecosystem processes. For any ecosystem, the ultimate source of energy is sunlight. And as you know, it enters the ecosystem through the producers. When a primary consumer (herbivore) eats a producer, and is itself eaten by secondary consumers, we can say that energy is flowing through the ecosystem. The information provided therein, would serve you as a base material for understanding this and the subsequent sections of this unit. As you already know that the amount of solar energy received at the outer boundary of earth's atmosphere is at the rate of 2cal/cm2/min. This quantity is fixed and known as solar constant. You have also learnt that about 30 per cent often sunlight reaching the earth's atmosphere is reflected back into space, about 51 per cent is absorbed as heat by ground, vegetation or water, and about 19 per cent is absorbed by the atmosphere.
Only a small fraction of sunlight, that is, about 0.b2 per tent reaching the atmosphere is used in photosynthesis. Nevertheless; it is this small fraction on which all the organisms of the ecosystem depend. The actual amount of solar flux' received at the surface of the earth is dependent on various climatic, geographic and other environmental factors. On an average the total amount of solar energy that reaches the earth's surface is about 3,400 kcal/m2/day. It varies significantly from one place to another, for example, it decreases with latitude and its input also varies during different seasons at any given location.