question_answer

(i) Food web and trophic levels are interconnected. Justify.

(ii) Give diagrammatic representation of trophic levels in an ecosystem with the appropriate diagrams.

Or

Detritus gets decomposed step - by - step by different agents and made available as nutrients to the plant. Describe briefly.

Answer:

(i) (a) Food web is a network of food chains which becomes interconnected at various trophic levels, so as to form a number of feeding connections amongst the different organisms of a biotic community.

(b) Trophic level is the specific position of an organism based on its source of nutrition in the food chain. All organisms occupy a particular place in their natural surrounding or in a community according to their feeding relationship with other organisms. Thus, food web and trophic levels are interconnected.

(ii) Representation of trophic levels in an ecosystem is given below

Or

Detritus is a raw material for decomposition. It includes dead remains of plants (leaves, barks and lowers) and animals including faecal matter. It is largely an aerobic process, i.e. requires oxygen for its processing. Different steps involved in the process of decomposition are as follows

(i) Fragmentation It is the process of breaking down of detritus into smaller particles.

(ii) Leaching It is the process by which water soluble inorganic nutrients go down into the soil horizons and get precipitated as unavailable salts.

(iii) Catabolism It is the process of degradation of detritus into simple organic material by the action of bacterial and fungal enzymes and their further conversion into organic compounds.

(iv) Humitication It is the process that leads to an accumulation of a dark coloured, amorphous and colloidal substance called humus this humus is highly resistant to microbial action .and decomposes at a very slow rate. It serves as a reservoir of nutrients.

(v) Mineralisation It is the process by which humus is further degraded by microbial action and releases inorganic nutrients.