Interaction in the earth ecosystem:
In this comparatively smaller section, we will give you the idea, that the earth as a whole is an ecosystem. Whatever you have learnt till now is also applicable to earth on a large scale. Let us see how. So far you have seen that the interaction of organisms with each other and with their environment is seemingly endless. As we see, the source of all energy is the sun. Solar energy, through photosynthesis, is stored in the food prepared by plants. This energy supports earth's organisms.
Sunlight also powers the water cycle, that ensures supply of fresh water and continually regulates warmth and moisture over the globe. Whether it is the life on land or in water, energy captured by photosynthesis flows through the consumers, thus making animal life possible. In a far more subtle interaction, the molecules of all organisms finally reach the decomposer where the last bit cf energy is exfracted by them. Not only that, the vital elements such as nitrogen, carbon etc. are also freed, to be recycled back to the waiting producers for another turn of the cycle of life. In the ongoing energy flow, each participant releases its quota of unused energy in the form of heat. This energy goes back to the physical world that is the atmosphere. Thus there is an equilibrium between the physical and the biological world in terms of nutrients and energy.
This state is also called natural equilibrium, a term we very often come across, when dealing with problems of ecology and environmental protection. Every individual in modern times, must understand these basics of existence, because he or she may otherwise unknowingly make choices which would provide a set back to these processes and eventually to the life on this planet.