UPSC Prelims 2017 Q21: Environment & Ecology – Ecosystems & Ecology Concepts
Due to some reasons, if there is a huge fall in the population of species of butterflies, what
could be its likely consequence/consequences?
1. Pollination of some plants could be adversely affected.
2. There could be a drastic increase in the fungal infections of some cultivated plants.
3. It could lead to a fall in the population of some species of wasps, spiders and birds.
Select the correct answer
using the code given below:
- (a) 1 only
- (b) 2 and 3 only
- (c) 1 and 3 only
- (d) 1, 2 and 3
Answer: (c) 1 and 3 only
Explanation
What if butterflies declined sharply?
| Statement | Verdict | Why |
|---|---|---|
| 1. Pollination of some plants could suffer | Correct | Butterflies are important pollinators of many flowering plants |
| 2. Fungal infections of crops could rise sharply | Incorrect | Butterflies do not control fungi; there is no such link |
| 3. Some wasps, spiders and birds could decline | Correct | Butterflies and caterpillars are prey for these animals; parasitic wasps depend on caterpillars |
Butterflies in the food web:
| Role | Example |
|---|---|
| Pollinator | Visits flowers for nectar |
| Prey | Eaten by birds, spiders, lizards |
| Host | Caterpillars host parasitoid wasps |
Answer: (c) 1 and 3 only.
Why each option is right or wrong
- (a) Incorrect. Statement 3 is also true; predators and parasitoids depend on butterflies.
- (b) Incorrect. Statement 2 is false; butterflies have no role in controlling fungal infections.
- (c) CORRECT. Fewer butterflies would hurt pollination and the animals that feed on them.
- (d) Incorrect. There is no link between butterfly decline and fungal infections of crops.
Key point
Butterflies are pollinators and prey; their decline hurts pollination and the wasps, spiders and birds that feed on them.
Remember
Butterflies: pollinators and prey.
Common mistakes
- Assuming every ecological change causes disease outbreaks in crops.
- Forgetting butterflies are food for many predators.
- Not knowing parasitoid wasps lay eggs in caterpillars.
Exam tip
Ask what the species does in the food web: what it eats, what eats it, what it pollinates.
Sources
- NCERT Class XII — Biology, Ch 13 (Organisms and Populations)
- Zoological Survey of India — Butterflies of India