UPSC CSE Prelims
Keystone and Flagship Species Previous Year Questions (PYQs)

Detailed Explanation:

Answer: Option 1 — 1 and 2 only

This question tests knowledge about the behavioral characteristics of big cats, particularly lions, cheetahs, and leopards. Understanding territorial marking, breeding patterns, and vocal capabilities of these species is important for wildlife ecology.

✅ Statement 1 – Correct: Lions do not have a strictly defined breeding season and can breed throughout the year, though some seasonal peaks may occur depending on environmental conditions like prey availability and rainfall.

✅ Statement 2 – Correct: Cheetahs lack the specialized larynx structure (hyoid bone apparatus) that allows other big cats to roar; instead, they produce chirps, purrs, and high-pitched calls similar to birds.

❌ Statement 3 – Incorrect: Male leopards, like male lions, actively use scent marking (urine spraying, scraping, and fecal deposits) to proclaim and defend their territories; this statement incorrectly suggests leopards do not engage in territorial scent marking.

📝 Short Notes: Big Cats - Behavioral Characteristics

• Roaring mechanism: Lions, tigers, leopards, and jaguars belong to genus Panthera with a flexible hyoid bone that enables roaring.
• Cheetah distinction: Belongs to genus Acinonyx; has a fixed hyoid bone, preventing roaring but allowing continuous purring.
• Territorial behavior: All big cats use scent marking (urine, feces, gland secretions) and visual cues (scratch marks) to establish territories.
• Breeding patterns: Most big cats can breed year-round, but environmental factors (prey density, climate) influence peak breeding times.

Detailed Explanation:

Answer: Option 3 — All three

All three groups mentioned in the question—butterflies, fish, and frogs—have poisonous species among them. Butterflies like the Monarch sequester toxins from their larval diet of milkweed, making them poisonous to predators. Many fish species such as pufferfish, lionfish, and stonefish possess deadly venom or toxins. Poison dart frogs are classic examples of amphibians that secrete potent toxins through their skin as a defense mechanism.

📝 Short Notes: Poisonous Species in Different Animal Groups

• Poisonous Butterflies: Monarch butterflies accumulate cardiac glycosides from milkweed plants during their caterpillar stage, making them toxic to birds and other predators. Other examples include the Pipevine Swallowtail.
• Poisonous Fish: Pufferfish contain tetrodotoxin, a neurotoxin deadly to humans. Lionfish and stonefish have venomous spines. Stingrays possess venomous barbs on their tails.
• Poisonous Frogs: Poison dart frogs (family Dendrobatidae) of Central and South America secrete alkaloid toxins through their skin. The Golden Poison Frog is one of the most toxic vertebrates on Earth.
• Mechanism of Toxicity: Some species produce toxins endogenously (within their bodies), while others sequester them from their diet (like Monarch butterflies and poison dart frogs).
• Purpose of Poison: These toxins serve primarily as defense mechanisms against predators, advertised through warning coloration (aposematism) in many cases.

Detailed Explanation:

Answer: Option 3 — Insects

All three organisms—Cicada, Froghopper, and Pond Skater—are classified as insects belonging to different families within the class Insecta. Cicadas are known for their loud mating calls, froghoppers (spittlebugs) are famous for the foam they produce as nymphs, and pond skaters use surface tension to walk on water.

📝 Short Notes: Classification of Common Insects

• Cicada: Order Hemiptera; known for their distinctive loud buzzing sounds produced by males during mating season; have a long lifecycle with some species emerging every 13-17 years.
• Froghopper (Spittlebug): Order Hemiptera; small jumping insects; nymphs produce foam (cuckoo spit) on plants for protection; adults are powerful jumpers.
• Pond Skater (Water Strider): Order Hemiptera, family Gerridae; use surface tension and hydrophobic legs to walk on water; predators of small aquatic organisms.
• Common Feature: All three belong to Order Hemiptera (true bugs), characterized by piercing-sucking mouthparts and incomplete metamorphosis.
• Ecological Role: These insects play important roles as herbivores, predators, and prey in their respective ecosystems.

Detailed Explanation:

Answer: Option 2 — Only two

The question tests knowledge about the behavioral ecology of Indian squirrels. Out of the three statements, two are correct (statements 2 and 3), while statement 1 is incorrect as Indian squirrels are primarily arboreal and build tree nests rather than ground burrows.

❌ Statement 1 – Incorrect: Indian squirrels like the Indian Palm Squirrel (Funambulus) and Malabar Giant Squirrel (Ratufa indica) are arboreal species that build nests (dreys) in tree branches, hollows, or crevices using twigs and leaves, not ground burrows.

✅ Statement 2 – Correct: Indian squirrels exhibit scatter hoarding behavior, burying nuts and seeds in shallow ground locations for later retrieval, which also aids in seed dispersal and forest regeneration.

✅ Statement 3 – Correct: Squirrels are opportunistic omnivores; while their primary diet includes seeds, nuts, fruits, and fungi, they also consume insects, caterpillars, bird eggs, and occasionally small vertebrates.

📝 Short Notes: Indian Squirrels - Ecology & Behavior

• Common Species: Indian Palm Squirrel (Funambulus palmarum), Three-striped Palm Squirrel (F. tristis), Malabar Giant Squirrel (Ratufa indica), and Indian Giant Squirrel (Ratufa macroura)
• Habitat: Predominantly arboreal (tree-dwelling); found in forests, urban parks, gardens, and agricultural landscapes
• Nesting: Build dreys (leaf and twig nests) in tree branches or use tree hollows; do not make ground burrows unlike ground squirrels found in other regions
• Food Storage: Practice scatter hoarding - bury food items in multiple scattered locations rather than one central cache; excellent spatial memory for retrieval
• Diet: Omnivorous - primarily herbivorous (nuts, seeds, fruits, flowers, bark) but also consume insects, bird eggs, and occasionally small animals
• Ecological Role: Important seed dispersers for many tree species; forgotten caches germinate into new plants, aiding forest regeneration
• Conservation Status: Most species are Least Concern, but habitat specialists like the Malabar Giant Squirrel face threats from habitat fragmentation

Detailed Explanation:

Answer: Option 1 — Only one

Among the three fauna listed, only the Malabar Civet is a nocturnal animal, being primarily active during the night. The Lion-tailed Macaque is a diurnal species, active during the day, while the Sambar Deer is crepuscular, most active during dawn and dusk rather than after sunset.

Analysis of Each Species:
🦁 Lion-tailed Macaque: Diurnal primate found in Western Ghats, active during daylight hours.
🐆 Malabar Civet: Nocturnal carnivore endemic to Western Ghats, most active after sunset. ✅
🦌 Sambar Deer: Crepuscular herbivore, most active at dawn and dusk, not strictly nocturnal.

📝 Short Notes: Activity Patterns in Animals

Detailed Explanation:

Answer: Option 2 — Orangutan

Orangutans are highly intelligent great apes known for their remarkable tool-use capabilities. They have been extensively observed using sticks to scrape and extract insects from holes in trees and logs, probe for honey, and even fashion leaves into gloves or napkins. This behavior demonstrates their advanced cognitive abilities and problem-solving skills, making them one of the most tool-proficient non-human primates.

📝 Short Notes: Tool Use in Animals

• Orangutans: Use sticks to extract insects, honey, and seeds; use leaves as umbrellas, gloves, and napkins; found in Borneo and Sumatra.
• Chimpanzees: Use sticks to fish for termites, stones to crack nuts, and leaves as sponges for drinking water.
• Crows: Craft hooked tools from twigs to extract insects; demonstrate advanced problem-solving abilities.
• Sea Otters: Use rocks as anvils to crack open shellfish while floating on their backs.
• Elephants: Use branches to swat flies, scratch themselves, and modify sticks to reach food.
• Dolphins: Use marine sponges to protect their rostrums while foraging on the seabed.

Detailed Explanation:

Answer: Option 3 — Statement-I is correct but Statement-II is incorrect

This question tests knowledge about the biogeographical distribution of marsupials and their ecological adaptations. Statement I correctly identifies that marsupials are not naturally found in India, while Statement II incorrectly restricts their habitat requirements.

✅ Statement I – Correct: Marsupials are indeed not naturally found in India. They are primarily native to Australia (kangaroos, koalas, wombats), the Americas (opossums), and Papua New Guinea. India falls outside the natural distribution range of marsupials.

❌ Statement II – Incorrect: This statement is factually wrong on multiple counts. Marsupials do not require montane grasslands exclusively and can thrive in diverse habitats including forests, deserts, savannas, wetlands, and even urban areas. They also coexist with various predators in their natural habitats (e.g., dingoes in Australia). The claim that they can thrive "only" in montane grasslands with no predators is completely false.

📝 Short Notes: Marsupials - Distribution and Ecology

• Definition: Marsupials are mammals characterized by giving birth to relatively undeveloped young that continue development in a pouch (marsupium).
• Primary Distribution: Australia (~70% of all marsupial species), Americas (opossums), Papua New Guinea, and nearby islands.
• Habitat Diversity: Marsupials occupy varied habitats - rainforests (tree kangaroos), deserts (bilbies), grasslands (kangaroos), forests (koalas), and wetlands (water opossums).
• Examples: Kangaroos, wallabies, koalas, wombats, Tasmanian devils, possums, and opossums.
• Evolutionary Significance: Marsupials represent an ancient mammalian lineage that thrived in Gondwanaland before continental drift isolated populations.
• Indian Context: No native marsupials exist in India due to biogeographical separation and different evolutionary pathways in the Indian subcontinent.

Detailed Explanation:

Answer: Option 3 — Honeybees

The waggle dance is a unique form of communication performed by worker honeybees to inform other members of the colony about the direction and distance to food sources. This remarkable behavior was decoded by Austrian scientist Karl von Frisch, who won the Nobel Prize for this discovery. The direction of the dance relative to the vertical indicates the angle to the food source in relation to the sun, while the duration of the waggle portion indicates the distance.

📝 Short Notes: Honeybee Waggle Dance

• Discovered by: Karl von Frisch (Austrian ethologist, Nobel Prize 1973)
• Purpose: Communication among worker bees about food source location (nectar, pollen, water)
• Direction indication: Angle of the waggle run relative to vertical = angle to food source relative to the sun's position
• Distance indication: Duration and number of waggles indicate distance to the source (longer dance = farther distance)
• Round dance: Performed for food sources very close to the hive (within 50-100 meters)
• Significance: Demonstrates complex social communication in insects and symbolic language in non-human species

Detailed Explanation:

Answer: Option 1 — Ant

Certain ant species, particularly leaf-cutter ants and others in the tribe Attini, are well-known for cultivating fungi. These ants practice sophisticated agriculture by cutting plant material, using it as substrate to grow specific fungus species in underground gardens, which then serve as their primary food source. This remarkable mutualistic relationship represents one of the most advanced examples of non-human agriculture in nature.

Why other options are incorrect:
• Cockroaches are omnivorous scavengers that do not cultivate fungi
• Crabs are aquatic scavengers or predators without fungal cultivation behavior
• Spiders are predators that capture prey and do not engage in fungal farming

📝 Short Notes: Fungus-Growing Ants

• Primary Species: Leaf-cutter ants (Atta and Acromyrmex genera) and fungus-growing ants (Tribe Attini) cultivate fungi as their primary food source
• Agricultural Process: Worker ants cut fresh plant material, chew it into a pulp, and use it as substrate for fungal cultivation in specialized underground chambers
• Fungal Species: They cultivate specific fungi from the family Lepiotaceae, which cannot survive outside the ant colonies
• Mutualistic Symbiosis: The ants provide the fungus with nutrients and protection, while the fungus provides specialized structures (gongylidia) as food for the ants
• Antibiotic Production: Some fungus-growing ants harbor bacteria (Actinomycetes) on their bodies that produce antibiotics to protect their fungal gardens from parasitic fungi
• Evolutionary Significance: This ant-fungus mutualism evolved approximately 50-60 million years ago and represents convergent evolution with human agriculture

Detailed Explanation:

Answer: Option 4 — 1 and 3

Among the given animals, hedgehogs and pangolins roll up into a tight ball as a defensive mechanism to protect their vulnerable parts from predators. Hedgehogs use their sharp spines, while pangolins use their tough keratin scales for protection. Marmots, on the other hand, do not roll up; they rely on burrows and alarm calls to avoid predators.

✅ Hedgehog – Correct: Rolls into a tight ball with spines covering vulnerable soft belly parts when threatened.
❌ Marmot – Incorrect: Does not roll up; uses burrows and vocal warning calls as primary defense against predators.
✅ Pangolin – Correct: Rolls into a protective ball, using overlapping keratin scales as armor to shield vulnerable underside.

📝 Short Notes: Defensive Mechanisms in Animals

• Hedgehog: Small spiny mammals found in Europe, Asia, and Africa; covered with about 5,000-7,000 spines made of keratin; rolls into a ball when threatened, making it difficult for predators to attack.
• Pangolin: Only mammal covered in scales; found in Asia and Africa; scales made of keratin (same material as human nails); listed as critically endangered due to illegal wildlife trade; all eight species protected under CITES.
• Marmot: Large ground squirrels found in mountainous areas; social animals living in burrows; use sentinel behavior where one individual watches for predators while others forage; emit high-pitched whistles as alarm calls.
• Other Rolling Animals: Armadillos (three-banded armadillo can roll completely), pill millipedes, pill bugs (woodlice), and some species of armored caterpillars also use rolling as defense.
• Types of Defense Mechanisms: Physical barriers (spines, scales, shells), camouflage, warning coloration, chemical defense (toxins), behavioral (fleeing, freezing, rolling), and group defense.

Detailed Explanation:

Answer: Option 3 — Oyster

Oysters are filter feeders that strain suspended matter and food particles from water by passing it over specialized filtering structures called gills. Among the given options, only oysters possess this feeding mechanism, while catfish are bottom feeders, octopuses are predators, and pelicans are visual hunters that catch fish.

📝 Short Notes: Filter Feeders

• Definition: Filter feeders are organisms that feed by straining suspended matter and food particles from water through specialized filtering structures.
• Common Examples: Clams, oysters, mussels, sponges, krill, baleen whales, and certain fish including some sharks.
• Avian Filter Feeders: Flamingos and certain duck species use filter feeding mechanisms.
• Ecological Role: Filter feeders act as ecosystem engineers by clarifying water and removing suspended particles, improving water quality.
• Bioaccumulation: They serve as indicator organisms due to their role in bioaccumulation of pollutants and toxins from water.
• Pearl Production: Oysters and mussels are commercially important for pearl farming, practiced in states like Gujarat, Maharashtra, Kerala, Odisha, and others in India.

Detailed Explanation:

Answer: Option 3 — 2 and 3

Lichens and mosses are uniquely adapted to survive on bare surfaces without soil. Lichens, being symbiotic associations of fungi and algae/cyanobacteria, can colonize rocks and tree bark by absorbing nutrients directly from air and rain. Mosses, though non-vascular plants, possess specialized structures that enable them to absorb water and nutrients from their immediate environment without requiring soil.

Analysis of Organisms:
1. Fern – Cannot survive without soil: Ferns are vascular plants requiring soil to anchor their roots and absorb water through their well-developed root systems.

2. Lichen – ✅ Can survive without soil: Lichens are symbiotic organisms (fungus + algae/cyanobacteria) that obtain nutrients directly from air and precipitation, thriving on rocks, bark, and other bare surfaces.

3. Moss – ✅ Can survive without soil: Mosses are bryophytes (non-vascular plants) with rhizoids that can attach to bare surfaces and absorb water and minerals directly from the environment.

4. Mushroom – Cannot survive without soil: Mushrooms are fungal fruiting bodies that require organic substrates (decaying matter, soil rich in nutrients) for the mycelium to grow and produce fruiting structures.

📝 Short Notes: Organisms Surviving Without Soil

• Lichens are pioneer species in ecological succession, colonizing bare rocks and weathering them into soil over time.
• Lichens as bioindicators: Highly sensitive to air pollutants like SO₂, NOₓ, and heavy metals; absence indicates poor air quality.
• Mosses reproduce via spores and require moisture for fertilization but can survive desiccation in dry conditions.
• Bryophytes (mosses, liverworts, hornworts) lack vascular tissues (xylem and phloem) but can thrive in moist, shaded environments on various substrates.
• Ferns are more advanced than mosses, having vascular tissues, but still require moist conditions and soil for optimal growth.

Detailed Explanation:

Answer: Option 1 — 1 and 2 only

Indian elephants live in matriarchal societies where the oldest and most experienced female leads the herd, while males typically live solitary lives or form bachelor groups. The gestation period of elephants is the longest among land mammals, ranging from 18 to 22 months.

✅ Statement 1 – Correct: Elephant herds are matriarchal, led by the oldest and most experienced female (matriarch), while adult males usually live alone or in bachelor groups.

✅ Statement 2 – Correct: Elephants have the longest gestation period among mammals, ranging from 18 to 22 months, with an average of about 22 months.

❌ Statement 3 – Incorrect: Female elephants can continue to reproduce well beyond 40 years of age, often calving into their 50s and sometimes even early 60s, though fertility may decline with age.

❌ Statement 4 – Incorrect: Karnataka has the highest elephant population in India (around 6,000), followed by Assam and Kerala. Kerala ranks third, not first.

📝 Short Notes: Indian Elephants

• Scientific Name: Elephas maximus indicus (subspecies of Asian elephant)
• Protection Status: Schedule I of Wildlife Protection Act, 1972; Appendix I of CITES; IUCN Red List - Endangered
• Social Structure: Matriarchal herds of 6-12 individuals led by the oldest female; adult males are solitary or form temporary bachelor groups
• Reproduction: Gestation period 18-22 months (longest among mammals); females reach sexual maturity at 10-12 years; can reproduce until 50-60 years of age; typically give birth to one calf every 4-5 years
• Distribution in India: Karnataka (highest population ~6,000), Assam (~5,700), Kerala (~3,000), Tamil Nadu, and northeastern states
• Project Elephant: Launched in 1992 to protect elephants, their habitats, and migration corridors; 33 elephant reserves established across 16 states
• Major Threats: Habitat loss and fragmentation, human-elephant conflict, poaching for ivory (though Indian elephants have smaller tusks than African elephants), railway and road accidents

Detailed Explanation:

Answer: Option 1 — Birds

All four species mentioned—Ceylon frogmouth, Coppersmith barbet, Gray-chinned minivet, and White-throated redstart—are birds found in India and neighboring regions. The Ceylon frogmouth is a nocturnal bird of the Western Ghats, the Coppersmith barbet is named for its metallic call, the Gray-chinned minivet is known for its colorful plumage, and the White-throated redstart is characterized by its distinctive red tail.

📝 Short Notes: Indian Bird Species

• Ceylon Frogmouth (Batrachostomus moniliger): A nocturnal bird native to the Western Ghats and Sri Lanka; resembles a frog due to its wide mouth and camouflaged plumage; inhabits dense tropical forests.
• Coppersmith Barbet (Psilopogon haemacephalus): A resident bird across the Indian subcontinent; named for its repetitive metallic 'tuk-tuk-tuk' call resembling a coppersmith's hammer; features crimson forehead and throat with green body.
• Gray-chinned Minivet (Pericrocotus solaris): Found in the Himalayas and Southeast Asia; exhibits sexual dimorphism with males displaying orange-red plumage and females showing yellow; inhabits subtropical and temperate forests.
• White-throated Redstart (Phoenicurus schisticeps): A small passerine bird found in the Himalayas, Nepal, Bhutan, and parts of China; males have black plumage with white throat and bright rufous-red tail; prefers high-altitude scrublands and rocky areas.
• Biodiversity Significance: These species represent India's rich avian diversity across different ecological zones—from tropical forests to high-altitude regions—highlighting the importance of habitat conservation.

Detailed Explanation:

Answer: Option 3 — 1 and 3 only

This question tests knowledge of wildlife species and their natural habitats in India. Out of the three pairs given, only pairs 1 and 3 are correctly matched, while pair 2 incorrectly associates the Irrawaddy Dolphin with the Chambal River.

✅ Pair 1 – Correct: Blue-finned Mahseer is indeed naturally found in the Cauvery River and other rivers of the Deccan Plateau. It is an endangered freshwater fish species.

❌ Pair 2 – Incorrect: Irrawaddy Dolphin is NOT found in the Chambal River. The Chambal River is known for the Gangetic Dolphin. Irrawaddy Dolphins are found in coastal areas of South and Southeast Asia, and in India, they are found in Lake Chilika (Odisha).

✅ Pair 3 – Correct: Rusty-spotted Cat is naturally found in the Eastern Ghats. This small wild cat species is also found in the Western Ghats, central India, and Sri Lanka.

📝 Short Notes: Indian Wildlife Species and Habitats