UPSC Prelims 2024 Q19: Environment & Ecology – Biodiversity & Conservation
Consider the following plants :
1. Groundnut
2. Horse - gram
3. Soybean
How many of the above belong to the pea family ?
- (a) Only one
- (b) Only two
- (c) All three
- (d) None
Answer: (c) All three
Explanation
Pea family — Fabaceae (Leguminosae)
| Plant | Botanical name | Family | Legume? |
|---|---|---|---|
| Groundnut | *Arachis hypogaea* | Fabaceae | Yes — pods ripen underground |
| Horse-gram | *Macrotyloma uniflorum* | Fabaceae | Yes — a hardy dryland pulse |
| Soybean | *Glycine max* | Fabaceae | Yes — a protein-rich oilseed |
Why legumes matter:
| Feature | Detail |
|---|---|
| Root nodules | Hold Rhizobium bacteria that fix atmospheric nitrogen |
| Soil benefit | Improve soil fertility; used in crop rotation |
| Food value | Rich in protein — pulses and oilseeds |
All three plants belong to the pea family.
Answer: (c) All three.
Why each option is right or wrong
- (a) Incorrect. All three are legumes, not just one.
- (b) Incorrect. Groundnut, horse-gram and soybean are all members of Fabaceae.
- (c) CORRECT. All three belong to the pea family (Fabaceae) and fix nitrogen with Rhizobium.
- (d) Incorrect. Each of them is a legume with root nodules.
Key point
Groundnut, horse-gram and soybean are all legumes (Fabaceae) that fix nitrogen through Rhizobium root nodules.
Remember
Groundnut, horse-gram and soybean all belong to the pea family.
Common mistakes
- Thinking groundnut is a nut; botanically it is a legume whose pods develop underground.
- Classing soybean only as an oilseed and forgetting it is also a legume.
- Not recognising horse-gram (kulthi) as a pulse of dry South Indian farmland.
Exam tip
Pod + nodules = Fabaceae. Most pulses and groundnut and soybean are in it.
Sources
- NCERT Class XI — Biology, Ch 5 (Morphology of Flowering Plants — Fabaceae)
- Encyclopaedia Britannica — Fabaceae