2010 General Studies, all questions
UPSC Prelims 2010 · General Studies
Question 65: Science and Technology
Some species of plants are insectivorous. Why ?
aTheir growth in shady and dark places does not allow them to undertake sufficient photosynthesis and thus they depend on insects for nutrition
bThey are adapted to grow in nitrogen deficient soils and thus depend on insects for sufficient nitrogenous nutrition
cThey cannot synthesize certain vitamins themselves and depend on the insects digested by them
dThey have remained in that particular stage of evolution as living fossils, a link between autotrophs and heterotrophs
AnswerThe answer is (b).
Insectivorous plants such as the pitcher plant, sundew and Venus flytrap typically grow in bogs and other soils poor in nitrogen. They photosynthesise normally, but they trap and digest insects to obtain the nitrogen (and some other minerals) that the soil cannot supply. They do not depend on insects for energy, for vitamins, or because of their stage of evolution. Remember: insects supplement the nitrogen, not the food energy, of these plants.
Why each option is right or wrong
- (a) They photosynthesise; insects supply nitrogen, not energy.
- (b) Right: they live in nitrogen-poor soils and get nitrogen from insects.
- (c) Vitamins are not the reason.
- (d) They are not living fossils linking autotrophs and heterotrophs; the reason is nitrogen shortage.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2010, General Studies, Series A. The paper on upsc.gov.in.