Question map
Not attempted Correct Incorrect ★ Bookmarked
Loading…
Q29 (IAS/2024) Environment & Ecology › Ecology & Ecosystem Basics › Animal adaptations Official Key

Consider the following : 1. Butterflies 2. Fish 3. Frogs How many of the above have poisonous species among them ?

Result
Your answer: —  ·  Correct: C
Explanation

The correct answer is option C because all three groups—butterflies, fish, and frogs—contain poisonous species.

**Butterflies**: Several butterfly species, particularly monarchs, are poisonous due to toxins they accumulate from their larval host plants (like milkweed), which makes them toxic to predators.

**Fish**: High levels of mercury in fish stocks have been found mainly in coastal areas.[1] Additionally, many fish species like pufferfish contain natural toxins (tetrodotoxin) that can be harmful or fatal to humans.

**Frogs**: Poison Dart Frogs got their name because hounds would tip their arrows in the frog's poisons.[2] These frogs secrete potent toxins through their skin as a defense mechanism against predators.

Since all three groups have documented poisonous species, the answer is "All three," making option C correct.

Sources
  1. [1] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 29: Environment Issues and Health Effects > 29.r.4. Mercury > p. 413
  2. [2] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 12: Animal Diversity of India > Do you know? > p. 187
How others answered
Each bar shows the % of students who chose that option. Green bar = correct answer, blue outline = your choice.
Community Performance
Out of everyone who attempted this question.
53%
got it right
PROVENANCE & STUDY PATTERN
Full view
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. Consider the following : 1. Butterflies 2. Fish 3. Frogs How many of the above have poisonous species among them ? [A] Only one [B] Onl…
At a glance
Origin: Mixed / unclear origin Fairness: Moderate fairness Books / CA: 6.7/10 · 0/10

This is a classic 'Existence Heuristic' question. It doesn't require memorizing a list of every toxic animal; it tests the biological principle that in massive taxonomic groups (thousands of species of fish/insects), chemical defense is a common evolutionary adaptation. If you know one famous example (e.g., Monarch Butterfly or Pufferfish), the logic holds.

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
Are there butterfly species that are poisonous (have toxic chemical defenses)?
Origin: Weak / unclear Fairness: Borderline / guessy
Indirect textbook clues
Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 9: Indian Biodiversity Diverse Landscape > ENVIRONMENT > p. 156
Strength: 4/5
“• An insect's consists of 3 body parts and 6 legs and an antennae • E.g.: beetle, butterfly, moth, dragonfly, bee, wasp and praying mantis.”
Why relevant

This snippet explicitly lists 'butterfly' as an insect, establishing that butterflies belong to the biological group (insects) commonly discussed in toxicology and ecology contexts.

How to extend

A student can use the fact that butterflies are insects to ask whether known insect defensive strategies (e.g., chemical defenses) also occur in butterflies and then check entomological sources.

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 6: Environmental Issues > Neonicotinoids > p. 120
Strength: 4/5
“uo Neonicotinoids are a new class of insecticides chemically related to nicotine. The name literally means "new nicotine-like insecticides". Like nicotine, the neonicotinoids act on certain kinds of receptors in the nerve synapse. They are much more toxic to invertebrates, like insects, than they are to mammals, birds and other higher organisms. Neonicotinoids share a common mode of action that affect the central nervous system of insects, resulting in paralysis and death. One thing that has made neonicotinoid insecticides popular in pest control is their water solubility which allows them to be applied to soil and be taken up by plants.”
Why relevant

Explains that certain chemicals (neonicotinoids) act on insect nervous systems and that insects can be differentially affected by chemicals, showing insects as a class interact biologically with toxic compounds.

How to extend

A student could extend this by noting that if insects respond to and accumulate chemicals, some insect species (potentially including butterflies) might carry or sequester toxins as defenses; this suggests searching for examples of chemically defended insects.

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 12: Animal Diversity of India > Do you know? > p. 187
Strength: 3/5
“oak lizards got their name because hounds would tip their arrows in the frog's poisons. Sadly, because people are cutting down rainforests for agriculture and ranching, Poison Dart Frogs are at risk. The Blue Poison Dart Frog is the most endangered due. ,z.t.z. Andaman White-toothed Shrew (Cracidura andamanensis), Jenkin's Andaman Spiny Shrew (Crocidura jenkinsi) and the Nicobar White-tailed Shrew (Crocidura nicobarica) • These animals are endemic to India. • They are usually active by twilight or in the night and have specialized habitat requirements. • Habitat: Leaf litter and rock crevices. • The Andaman White-toothed Shrew is found on Mount Harriet in the South Andaman Islands. • The Jenkins' Andaman Spiny Shrew is found on Wright and Mount Harriet in the South Andaman Islands.”
Why relevant

Gives an example (poison dart frogs) of animals that are poisonous because of skin/ingested toxins, demonstrating the ecological pattern that some small animals use chemical defenses.

How to extend

A student can generalize that chemical defence is a known ecological strategy and therefore plausibly look for analogous strategies in other small animals, including insects like butterflies.

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 29: Environment Issues and Health Effects > AH*ffis.- s ffiHVINOil[{HHT > p. 418
Strength: 3/5
“e AH*ffis.- s ffiHVINOil[{HHT • Ilioassays are very common in pollution studies. Ilioassays can be conducted by using any type of organisms. However, the fish and insect bioassays are very common.• The aim is to find out either lethal concentration or effective concentration causing mortality or other effects.• Ultimately they are to be used for determination of safe concentration of a chemical or maximum acceptable toxicant concentration (MATC).”
Why relevant

Describes bioassays using insects to determine lethal or effective concentrations of chemicals, implying insects are subjects of toxicological study and can be sensitive to or involved in accumulation of toxins.

How to extend

A student might infer that because insects are studied for toxicity and chemical interactions, some insect species may possess or accumulate toxins, motivating targeted literature checks for butterflies with chemical defenses.

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > Impact of Microparticles > p. 97
Strength: 2/5
“physical obstruction or indirect interference with physiology is always possible (as with sea birds showing satiation on ingesting plastics) the n'raterial will pass through the animal virtually unchanged. The concern, however, is that plastics exposed to sea water tends to concentrate toxic and non-toxic organic compounds present in the sea water at low concentrations. These, including PCBs, DDT, and nonylphenols, have very high partition coefficients and are very efficiently concentrated in the plastic material. Plastic-related distress to over 50 species has been documented worldwide. The focus has very much been on larger species in surface waters or beaches, despite the fact that 99 percent of marine species live in the benthils.”
Why relevant

Shows that environmental materials (plastics) can concentrate toxic organic compounds which affect animals, illustrating the broader point that organisms can accumulate toxins from their diet or environment.

How to extend

A student could extend this general accumulation pattern to consider whether herbivorous insects (like many butterfly larvae) might sequester plant-produced toxins, prompting a focused search for examples.

Statement 2
Are there fish species that are poisonous (contain toxins harmful to predators or humans)?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 4: Aquatic Ecosystem > 4.4.6. Is it safe to eat seafood? > p. 40
Presence: 5/5
“• It is generally safe to eat seafood.• However, consuming shellfish harvested from waters with high levels of harmful algae and fish that have lesions or were caught during an algal bloom can result in illness.”
Why this source?
  • Explicitly warns that consuming fish caught during algal blooms can result in illness
  • Links contaminated seafood consumption to human health risk
Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 29: Environment Issues and Health Effects > 29.r.4. Mercury > p. 413
Presence: 5/5
“This is the most common and most toxic in water bodies. It occurs in water as monomethyl mercury. Most industrial effluents have mercury. Methyl mercury vapors cause fatal poisoning. High levels of mercury in fish stocks have been found mainly in coastal areas. Mumbai, Kolkata, Karwar (in Karnataka) and North Koel (in Bihar) are some of the severely affected areas. The recent popularity of energy efficient compact to fluorescent lamps or CFLs has added another dimension to the controversy. Toxicity of mercury is much greater than any other substance, about 1000 times more potent than colchicines. All Rights Reserved. No part of this naterial may be reprodriced in an,v forrl or by an1, means, \. without perlnirslon u iriting.”
Why this source?
  • Identifies monomethyl mercury as highly toxic and notes its accumulation in edible fish tissue
  • Specifies severe human health impacts from methylmercury in fish stocks
Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 29: Environment Issues and Health Effects > 29.1.6. DDT > p. 414
Presence: 4/5
“Toxic pesticides such as BHC, PCB, DDT etc., are not easily degraded and are long-lasting in the environment. Their concentration therefore goes on increasing in water and soil with successive applications. DDT was sprayed for many years on marshes to control mosquitoes. The DDT has bio-magnified from water to fish eating birds and humans. DDT is known to depress the activity of estrogen, the female sex hormone and testosterone, male sex hormone. Fish die due to eating of DDT-killed insects; turtles die because of eating DDT-killed fish and so on. DDT deposited in butter fat of milk is a potential danger to infants.”
Why this source?
  • Explains biomagnification of persistent pesticides (DDT) from water to fish-eating organisms and humans
  • Shows that long-lasting pollutants can concentrate in fish and pose risks up the food chain
Statement 3
Are there frog species that are poisonous (have toxic skin secretions harmful to predators or humans)?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 12: Animal Diversity of India > Do you know? > p. 187
Presence: 5/5
“oak lizards got their name because hounds would tip their arrows in the frog's poisons. Sadly, because people are cutting down rainforests for agriculture and ranching, Poison Dart Frogs are at risk. The Blue Poison Dart Frog is the most endangered due. ,z.t.z. Andaman White-toothed Shrew (Cracidura andamanensis), Jenkin's Andaman Spiny Shrew (Crocidura jenkinsi) and the Nicobar White-tailed Shrew (Crocidura nicobarica) • These animals are endemic to India. • They are usually active by twilight or in the night and have specialized habitat requirements. • Habitat: Leaf litter and rock crevices. • The Andaman White-toothed Shrew is found on Mount Harriet in the South Andaman Islands. • The Jenkins' Andaman Spiny Shrew is found on Wright and Mount Harriet in the South Andaman Islands.”
Why this source?
  • Explicitly refers to frogs' poisons and the use of frog toxins on arrows, demonstrating poisonous skin secretions.
  • Names poison dart frogs (e.g., Blue Poison Dart Frog) as examples, linking a taxon to toxic defenses.
Pattern takeaway: UPSC loves 'Possibility' questions in Science/Environment. If the question asks 'Are there ANY species of X that do Y?', and X is a broad category, the answer is overwhelmingly 'Yes'. Avoid extreme negatives.
How you should have studied
  1. [THE VERDICT]: Logical Sitter. While Shankar IAS explicitly covers Frogs (Poison Dart) and implies Fish (toxicity/algal blooms), the Butterfly link is basic NCERT Biology (Monarch Butterfly warning coloration).
  2. [THE CONCEPTUAL TRIGGER]: Evolutionary Adaptations & Defense Mechanisms (Mimicry, Camouflage, Chemical Defense).
  3. [THE HORIZONTAL EXPANSION]: Memorize the 'Weird' Toxic/Venomous classes: 1. Birds (Hooded Pitohui), 2. Mammals (Slow Loris, Platypus, Solenodon), 3. Fish (Pufferfish/Tetrodotoxin, Stonefish), 4. Butterflies (Monarch - eats milkweed), 5. Cephalopods (Blue-ringed Octopus).
  4. [THE STRATEGIC METACOGNITION]: Stop looking for a single page that lists 'All Poisonous Animals'. Instead, apply the 'Law of Large Numbers' in Biology: If a group (like Fish or Butterflies) has 20,000+ species, the probability of *none* of them being poisonous is statistically zero. Assume 'Yes' for broad biological possibilities.
Concept hooks from this question
📌 Adjacent topic to master
S1
👉 Natural chemical defenses in animals (toxicity as a defense)
💡 The insight

Some animals produce or sequester toxic chemicals as a defensive trait, so the existence of poisonous species is a biological adaptation to consider.

High-yield: links ecology, species interactions and conservation; helps distinguish naturally toxic organisms from those harmed by pollutants and frames questions about adaptive significance and protection measures.

📚 Reading List :
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 12: Animal Diversity of India > Do you know? > p. 187
🔗 Anchor: "Are there butterfly species that are poisonous (have toxic chemical defenses)?"
📌 Adjacent topic to master
S1
👉 Anthropogenic chemical pollutants and bioaccumulation
💡 The insight

Human-made chemicals such as PCBs, DDT and mercury can concentrate in ecosystems and cause toxicity across trophic levels, affecting wildlife health and conservation.

High-yield: central to environment and ecology topics; connects pollution sources, biomagnification, and impacts on species (including insects), and is commonly tested in questions on environmental hazards and policy.

📚 Reading List :
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > Impact of Microparticles > p. 97
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 29: Environment Issues and Health Effects > 29.r.4. Mercury > p. 413
  • INDIA PEOPLE AND ECONOMY, TEXTBOOK IN GEOGRAPHY FOR CLASS XII (NCERT 2025 ed.) > Chapter 9: Geographical Perspective on Selected Issues and Problems > Water Pollution > p. 96
🔗 Anchor: "Are there butterfly species that are poisonous (have toxic chemical defenses)?"
📌 Adjacent topic to master
S1
👉 Insect-targeting neurotoxic insecticides (neonicotinoids)
💡 The insight

Neonicotinoids are nicotine-like chemicals that act on insect nervous systems and are especially toxic to insects, affecting insect populations and pollinators.

High-yield: ties agriculture, pest management and pollinator conservation; useful for evaluating policy debates on pesticide regulation and ecological consequences for insects such as butterflies.

📚 Reading List :
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 6: Environmental Issues > Neonicotinoids > p. 120
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 9: Indian Biodiversity Diverse Landscape > ENVIRONMENT > p. 156
🔗 Anchor: "Are there butterfly species that are poisonous (have toxic chemical defenses)?"
📌 Adjacent topic to master
S2
👉 Biomagnification & bioaccumulation in aquatic food chains
💡 The insight

Explains how lipophilic and persistent pollutants concentrate in fish tissues and magnify up trophic levels, making fish toxic to predators and humans.

High-yield for environment and health topics: explains why pollutants like DDT and PCBs pose long-term risks through seafood consumption, links to pollution control and food safety policy, and enables answers on ecosystem and human-health impacts.

📚 Reading List :
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 2: Functions of an Ecosystem > 2.5.2. Biomagnification > p. 16
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 29: Environment Issues and Health Effects > 29.1.6. DDT > p. 414
🔗 Anchor: "Are there fish species that are poisonous (contain toxins harmful to predators o..."
📌 Adjacent topic to master
S2
👉 Harmful Algal Blooms (HABs) and seafood toxicity
💡 The insight

Describes algal-produced neurotoxins and hepatotoxins that contaminate shellfish and fish and cause poisonings in humans and marine life.

Important for questions on coastal pollution, fisheries management and public health: connects causes (eutrophication), impacts (shellfish/fish poisoning, fish kills) and mitigation (monitoring, closures), and supports case-based policy answers.

📚 Reading List :
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 4: Aquatic Ecosystem > Toxicity > p. 38
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 4: Aquatic Ecosystem > 4.4.4.Is HAB's an environmental hazard? > p. 39
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 4: Aquatic Ecosystem > 4.4.6. Is it safe to eat seafood? > p. 40
🔗 Anchor: "Are there fish species that are poisonous (contain toxins harmful to predators o..."
📌 Adjacent topic to master
S2
👉 Heavy metal contamination in fish (methylmercury)
💡 The insight

Specifies methylmercury accumulation in fish tissue and its severe toxicity to humans.

Useful for environment-health and industrial pollution questions: explains industrial sources, bioaccumulation in edible fish, public-health advisories and regulatory measures; links pollution, human health and fisheries economics.

📚 Reading List :
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 29: Environment Issues and Health Effects > 29.r.4. Mercury > p. 413
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > 5.15.6. Trigger Effect of Acid Rain on Pollutants: > p. 105
🔗 Anchor: "Are there fish species that are poisonous (contain toxins harmful to predators o..."
📌 Adjacent topic to master
S3
👉 Frog chemical defenses (poisonous skin secretions)
💡 The insight

Some frog species possess toxic skin secretions used as a defence, exemplified by poison dart frogs.

High-yield for ecology and biodiversity topics: explains predator–prey interactions, adaptations, and human-wildlife risk. Connects to questions on animal defence mechanisms, toxicology, and species-specific traits commonly asked in environment and biodiversity sections.

📚 Reading List :
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 12: Animal Diversity of India > Do you know? > p. 187
🔗 Anchor: "Are there frog species that are poisonous (have toxic skin secretions harmful to..."
🌑 The Hidden Trap

Venomous Mammals. Since they asked about Fish, Frogs, and Butterflies, the next logical bouncer is 'Are there any poisonous/venomous birds or mammals?' Answer: Yes (Hooded Pitohui, Slow Loris, Platypus).

⚡ Elimination Cheat Code

The 'Diversity Rule'. In a group as diverse as 'Fish' (34,000 species) or 'Butterflies' (17,500 species), it is biologically impossible for *zero* species to have evolved toxicity. If the option implies 'None', it is wrong. 'All three' is the safest bet for 'existence' questions in biodiversity.

🔗 Mains Connection

Bioprospecting & The Nagoya Protocol (Environment/IR). Many of these natural toxins (e.g., from Cone Snails or Frogs) are used by indigenous tribes (Traditional Knowledge) and are targets for pharmaceutical research (Biopiracy). This links biodiversity to Intellectual Property Rights.

✓ Thank you! We'll review this.

SIMILAR QUESTIONS

IAS · 2012 · Q16 Relevance score: -0.16

Consider the following kinds of organisms : 1. Bat 2. Bee 3. Bird Which of the above is/are pollinating agent/agents?

IAS · 2023 · Q14 Relevance score: -0.99

Consider the following fauna : 1. Lion-tailed Macaque 2. Malabar Civet 3. Sambar Deer How many of the above are generally nocturnal or most active after sunset?

IAS · 2023 · Q3 Relevance score: -1.51

Consider the following trees : 1. Jackfruit (Artocarpus heterophyllus) 2. Mahua (Madhuca indica) 3. Teak (Tectona grandis) How many of the above are deciduous trees?