Biotic and abiotic components are physically organized to provide a characteristics structure of ecosystems. Species composition and stratification are important structural features of an ecosystem. Ecosystem structure can be very well depicted through the food relationship of producers and consumers. Tropic (food) structure of ecosystem is based on the existence of several trophic levels in the ecosystem. The producers form the first trophic level, herbivorous the second trophic level and the describing in terms of the amount of living material, called standing crop, present in different trophic levels at a given time.
Ecosystems have natural tendency to persist which is made possible by a verity of functions performed by the structural components. For instance, green leaves functions as sites of food production and roots absorb nutrients from the soil. Herbivorous perform the function of utilizing parts of the plant’s production and in turn, serve as food for carnivores. De-composers break down complex organic materials into simpler inorganic products, which can be used by the producers. These functions are carried out in the ecosystem through delicately balanced and controlled processes.
Food Chain system:All trophic levels is an ecosystems are connected by transfer or energy. The transfer of enrgy from on trophic levelto next trophic levels is called food chain. Organisms which occupy a trophic level belong to that trophic level regardless to their taxonomic position. Thus, a grass hopper, a grazing cattle and grain eating birds, all are primary consumers (second trophic level) because they directly derive their energy from plants.
Two types of food chain can be distinguished in all ecosystems, grazing food chain and detritus food chain.
a)Grazing Food Chain System: Grazing food chain extends from producers through herbivorous to carnivores, cattle grazing in grasslands, seer browsing in forest and insect food on crops and trees are most common biotic constituent of grazing food chain.
(e.g. Plants) (e.g. grass hopper) (e.g. Lizard Snake)
The characteristics of grazing food chain are as follows:
1.The primary energy source of grazing food chain is solar radiations.
2.Green plants (or producers) synthesize their food by the process of photosynthesis and forms the first trophic level of the food chain.
3.Herbivorous are eaten by the carnivores which are of different categories.
4.These always end at decomposer level.
5.These are longer food chain.
Detritus or Saprophytic Chains: Detritus food chain begins with dead organic matter and passes through detritus-feeding organisms in soil to organisms feeding on detritus-feeders.
The characteristics of detritus food chain are as follows:
i)The primary energy source of detritus food chain is dead organic matter called detritus.
ii)Main sources of dead organic matter are fallen leaves or dead animal bodies.
iii)The primary consumers are detrivores e.g. protozoan’s protozoans, bacteria, fungi etc.
iv)The detrivores are eaten by secondary consumers which include insect larvae etc.
v)These are shorter than grazing food chain.
Figure (a generalized scheme of nutritional relationships among different biotic components of ecosystem).