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Q21 (IAS/2017) Environment & Ecology › Ecology & Ecosystem Basics › Plant–animal interactions Official Key

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 :

Result
Your answer: —  ·  Correct: C
Explanation

The correct answer is option C (statements 1 and 3 only).

**Statement 1 is correct:** Bees and butterflies are pollinators that transfer pollen and seeds from one flower to another, fertilizing plants so they can grow and produce food.[1] These insects help pollinate flowers from nearby areas moving pollen from one flower to another, which helps plants produce seeds.[2] Therefore, a huge fall in butterfly populations would adversely affect pollination of some plants.

**Statement 2 is incorrect:** There is no direct ecological connection between butterfly populations and control of fungal infections.[3] Butterflies are not known to control fungal infections in cultivated plants, so their decline would not lead to an increase in such infections.

**Statement 3 is correct:** Dragonflies usually eat flies, bees and butterflies.[4] This demonstrates that butterflies serve as prey in food chains. When butterfly populations fall drastically, predators that feed on them—including certain species of wasps, spiders, and birds—would face reduced food availability, potentially leading to declines in their populations as well.

Sources
  1. [1] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 6: Environmental Issues > 6.4. COLONY COLLAPSE DISORDER > p. 119
  2. [2] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 12: How Nature Works in Harmony > Activity 12.3: Let us read > p. 195
  3. [4] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 12: How Nature Works in Harmony > Activity 12.3: Let us read > p. 195
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Don’t just practise – reverse-engineer the question. This panel shows where this PYQ came from (books / web), how the examiner broke it into hidden statements, and which nearby micro-concepts you were supposed to learn from it. Treat it like an autopsy of the question: what might have triggered it, which exact lines in the book matter, and what linked ideas you should carry forward to future questions.
Q. Due to some reasons, if there is a huge fall in the population of species of butterflies, what could be its likely consequence/consequenc…
At a glance
Origin: Books + Current Affairs Fairness: Moderate fairness Books / CA: 6.7/10 · 3.3/10
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A classic 'Common Sense Ecology' question solvable via NCERT basics. Statements 1 and 3 are direct applications of Food Chains and Pollination. Statement 2 is an 'Extreme Exaggeration' trap designed to test your ability to filter out scientifically weak correlations.

How this question is built

This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.

Statement 1
Would a large decline in butterfly populations adversely affect the pollination of some plant species?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 6: Environmental Issues > 6.4. COLONY COLLAPSE DISORDER > p. 119
Presence: 5/5
“Bees are one of a myriad of other animals, including birds, bats, beetles, and butterflies, called pollinators. Pollinators transfer pollen and seeds from one flower to another, fertilizing the plant so it can grow and produce food. Cross-pollination helps at least 30 percent of the world's crops and go percent of our wild-plants to thrive. Without bees to spread seeds, many plants - including food crops - would die off. Bees are not summertime nuisance, they are small and hard-working insects actually make it possible for many of your favorite foods to reach your table. From apples to almonds to the pumpkin in our pumpkin pies, we have bees to thank.”
Why this source?
  • Explicitly lists butterflies among the animals called pollinators.
  • Explains pollinators transfer pollen and seeds, enabling plant fertilization and production.
  • Notes pollination by such animals is essential for a substantial fraction of crops and wild plants, implying loss of pollinators reduces plant reproduction.
Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 12: How Nature Works in Harmony > Activity 12.3: Let us read > p. 195
Presence: 4/5
“These insects help pollinate flowers from nearby areas moving pollen from one flower to another, which helps plants produce seeds. So, flowers near ponds with fish may produce more seeds than those near ponds without fish. • z What does this study show? How does the population of fish in a pond affect the seed production in nearby plants?• z This study shows how biotic components (fish, dragonflies, pollinators, plants) and abiotic components (temperature, water, nutrients) interact with and affect each other (Fig. 12.4). Similarly, can overfishing by humans change this balance? How do you think it may affect the living and non-living parts of the habitat?”
Why this source?
  • States insects move pollen between flowers and thereby increase seed production nearby.
  • Connects variation in insect (biotic) populations to measurable changes in plant seed output, supporting that insect declines can reduce pollination success.
Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 2: Functions of an Ecosystem > 2.6.r. Tlpes of biotic interaction > p. 16
Presence: 4/5
“r Mutualism: both species benefit. Example; in pollination mutualisms, the pollinator gets food (pollen, nectar), and the plant All Rights Reserved. No part of this material may be reproduced in any form or by any means, without permission in writing,”
Why this source?
  • Identifies pollination as a mutualism where both pollinator and plant benefit.
  • Provides the ecological mechanism (mutual dependence) linking declines in pollinators to adverse effects on plant reproduction.
Statement analysis

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Statement analysis

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