Despite the diversity of their components, all ecosystems function in the same way.
They are all open systems in that they take in energy in one form or another in order to convert it into organic matter and give off waste products. As a result, there are two basic types of links or flows between the component parts of the ecosystem – energy flow and biogeochemical cycling.
i. In addition, all ecosystems are self-regulating systems and have an ability up to a point to modify the condition of their internal energy and materials.
ii. The solar energy with the help of chlorophyll in plants under photosynthesis fixes some energy in plants.
The energy that is fixed is called Gross Primary Productivity (GPP) but since every plant has to perform some own function like growing up, etc. some of this energy is subtracted through respiration.
C6 H12 06 + 6Q2 -> 6H2Q + 6CQ2 + Heat |
i. GPP less that used in respiration is called Net Primary Product (NPP).
ii. The energy of NPP is stored in new living plant tissue or plant biomass which may be either direct Consumed or may die and accumulate as Detrital Organic Matter (DOM).
iii. The NPP provides the food base for all secondary biological productivity of animals.
Food Chains and Webs
i. Energy fixed in NPP is consumed by animals unable to manufacture their own food, i.e., herbivores (primary consumers) first, then carnivores (secondary consumers) then the top carnivores (tertiary consumers). The remains are consumed by decomposing organisms (e.g. bacteria and fungi).
ii. The flow of energy is called the food chain and the position one organism occupies in that is called the trophic level.
iii. In the process of eating and being eaten, energy flows – the passing from one trophic level to the next.
iv. The complex (many) food chains are called food web.
In primary biological productivity, the simple inorganic elements and compounds of carbon, oxygen hydrogen, nitrogen, etc. are converted into complex organic substances, e.g., plant and animal tissues. These eventually die and undergo bacterial decay and decomposition.
In this process of biological degradation, the inorganic elements are eventually released to be reused by the plants. Thus, there is a continuous circulation of elements from an inorganic (geo) to an organic (bio) form and back again. This is called biogeochemical cycling.
Some elements, such as C02 and 02 enter and leave the cycle in a gaseous form and follow a simple route from the atmosphere to the organisms and back.
Others such as hydrogen, N, P, K and Ca are absorbed in the form of soil (in solution), therefore, there circulation is dependent on hydrological cycle.