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Class 12th Biology 2016 Set3 Delhi Board Paper Solution

Question 21

 “In a food-chain, a trophic level represents a functional level, not a species.” Explain.
OR
(a) Name any two places where it is essential to install electrostatic precipitators. Why it is required to do so ?
(b) Mention one limitation of the electrostatic precipitator.

Answer

Position of a species in any trophic level is determined by the function performed by that mode of nutrition of species in a particular food chain. A given species may occupy more than one trophic level in the same ecosystem at a given time. If the function of the mode of nutrition of species changes, its position shall change in the trophic levels. The same species can be at the primary level of consumer in one food chain and at the secondary consumer level in another food chain in the same ecosystem at a given time.




OR


(a) Electrostatic precipitators can be installed in thermal power plants, smelters or other particulate matter releasing industries. They are important for removing particulate matter.


(b) Limitations :

Very, very small particulate matter which are less than 2.5 micrometres are not removed.  The velocity of air between the plates must be low enough to allow the dust to fall.  It cannot work without electricity.