(a) What are genetically modified crops ?
(b) Name four factors for which variety improvement is done.
(c) Write any two ways to control weeds.
CBSE Class IX Science LA (5 Marks)
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(a) Genetically modified crop : In this method, a gene that would provide the desired characteristics is introduced into the crop.
(b) Some of the factors for which crop variety improvement is done are :
(i) Higher Yield : Variety improvement has been done to increase the productivity of the crop per acre. This is very important in order to meet food demand for rapidly growing population.
(ii) Improved Quality : The definition of quality is different for different crops e.g., baking quality is important in wheat, protein quality in pulses, oil quality in oil seeds and preserving qualities in fruits and vegetable.
(iii) Wider Adaptability : Varieties that can grow under any condition and can adapt themselves to various environmental conditions, help in stabilizing the crop production.
(iv) Biotic and Abiotic Resistance : Biotic factors like (pathogens, insects and nematodes) and abiotic factors (drought, salinity, water logging, heat, cold and frost) affect crop production a lot. Varieties resistant to such factors are always preferred to improve crop production.
(c) Two ways to control weeds :
(i) Preventive methods : Proper seed bed preparation, timely sowing of crops, intercropping and crop rotation.
(ii) Chemical methods : Spraying of herbicides or weedicides. e.g., Atrazine. 2, 4 - D.
(b) Some of the factors for which crop variety improvement is done are :
(i) Higher Yield : Variety improvement has been done to increase the productivity of the crop per acre. This is very important in order to meet food demand for rapidly growing population.
(ii) Improved Quality : The definition of quality is different for different crops e.g., baking quality is important in wheat, protein quality in pulses, oil quality in oil seeds and preserving qualities in fruits and vegetable.
(iii) Wider Adaptability : Varieties that can grow under any condition and can adapt themselves to various environmental conditions, help in stabilizing the crop production.
(iv) Biotic and Abiotic Resistance : Biotic factors like (pathogens, insects and nematodes) and abiotic factors (drought, salinity, water logging, heat, cold and frost) affect crop production a lot. Varieties resistant to such factors are always preferred to improve crop production.
(c) Two ways to control weeds :
(i) Preventive methods : Proper seed bed preparation, timely sowing of crops, intercropping and crop rotation.
(ii) Chemical methods : Spraying of herbicides or weedicides. e.g., Atrazine. 2, 4 - D.
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