Citing lake as an example of a simple aquatic ecosystem, interpret how various functions of this ecosystem are carried out. Make a food chain that is functional in this ecosystem.
OR
(a) Colonization of a rocky terrain is a natural process. Mention the group of organisms which invade this area first. Give an example.
(b) Over the years, it has been observed that some of the lakes are disappearing due to urbanization. In absence of human interference, depict by making a flow chart, how do the successional seres progress from hydric to mesic condition.
(c) Identify the climax community of hydrarch and xerarch succession.
Lake is an example of an aquatic ecosystem. Any ecosystem includes both abiotic and biotic factors which determine its productivity.
The important abiotic factors are light, temperature, wind and important gases. Light is essential for carrying out photosynthesis. Solar energy is the major source of energy in the lake ecosystem. Temperature is important as most of the organisms of the lake are poikilothermic.
Among biotic components the first place is occupied by bacteria, then comes the primary producers, invertebrates, then fishes and other vertebrates.
As mentioned above the maximum energy gained by the lake ecosystem comes from photosynthesis carried out by aquatic plants and algae. Bacteria help in nutrient cycling in the lake by decomposing organic matter. Invertebrates like zooplankton for example Daphnia.,are also present. Then comes the fishes which feed mainly on zooplankton insects and other fishes. They also feed on detritus and come under detrivores.
The diagram is shown below:
OR
(a) Colonisation of rocky terrain refers to primary succession. It is the formation of a new biotic community. The group of organisms which invade this area first are lichens. They help in the formation of soil by causing weathering of rocks as they secrete certain acids which dissolve rocky substances.
(b) Succession is of two types – Hydrarch and xerarch. Hydrarch succession occurs in areas where there is water, and xerarch succession occurs in areas which are dry. The ultimate position of both the succession is towards medic which is neither too dry nor to wet. It is an intermediate of hydric and xeric conditions.
(c) The climax community of Hydrarch and xerarch succession is the mesic company.
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