UPSC Prelims 2013 · GS Paper I
Question 94: Science and Technology
Which of the following leaf modifications occurs/occur in desert areas to inhibit water loss?
- 1.Hard and waxy leaves
- 2.Tiny leaves or no leaves
- 3.Thorns instead of leaves
Select the correct answer using the codes given below.
AnswerUPSC’s answer is (d).
Desert plants (xerophytes) cut water loss by changing their leaves. Hard, waxy, thick-cuticled leaves reduce evaporation, tiny leaves or no leaves at all reduce the surface that loses water, and in cacti the leaves become thorns while the green stem carries out photosynthesis. All three modifications occur.
- 1. Hard, waxy leaves reduce evaporation.
- 2. Tiny or absent leaves reduce water loss.
- 3. Leaves turn into thorns in cacti and similar plants.
How you could have got this
- If you were sure statement 2 is correct, (c) goes: it leaves 2 out.
What you needed to know: Tiny or absent leaves reduce water loss.
- Then, if you were sure statement 3 is correct, (a) and (b) go: each of them leaves 3 out.
What you needed to know: Leaves turn into thorns in cacti and similar plants.
Only (d) is left. You didn’t need statement 1.
Which options go is worked out from UPSC’s key and the options, not by a model.
Why each option is right or wrong
- (a) Wrong. Thorns instead of leaves also occur.
- (b) Wrong. Hard, waxy leaves and thorns also occur.
- (c) Wrong. Tiny or absent leaves also occur.
- (d) Correct. All three modifications occur in desert plants.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2013, General Studies Paper I, Series A. The paper on upsc.gov.in.