UPPSC 2024 Prelims GS Paper-I · Question 62 of 150

Correct — C, Terrestrial habitants. A habitat is simply the surroundings in which an organism lives, and school science divides habitats into two broad kinds by the medium the organism lives in: terrestrial habitats, which are on land — forests, grasslands, deserts, coastal strips, mountains — and aquatic habitats, which are in water — ponds, lakes, rivers, swamps, estuaries and oceans. 'Terrestrial' comes from the Latin terra, earth or land. So plants and animals that live on land are the terrestrial ones: a mango tree, a cactus, a camel, a deer, an elephant, an earthworm. That is exactly what the question asks and (c) is the marked answer. The reason this item is not as trivial as it looks is option (d). Plants and animals ARE biotic — 'biotic' is the correct word for the living components of any habitat, as against the abiotic or non-living components. But 'biotic' tells you nothing about land or water: a fish in a river is every bit as biotic as a banyan tree on a hill. The question supplies one specific piece of information — 'live on land' — and the only option that uses that information is 'terrestrial'. Whenever an option is true of the subject but ignores the distinguishing detail the question gives you, it is a distractor, not the answer. Choose the option that discriminates.

• (a)Abiotic — Abiotic names the NON-LIVING part of a habitat — air, water, soil, sunlight, temperature, minerals. Plants and animals are living organisms by definition, so they can never be abiotic. This option is the exact opposite of what the question describes and is included only because 'abiotic' and 'biotic' look and sound alike under exam pressure.
• (b)Aquatic habitants — Aquatic is the complementary category: organisms that live IN WATER — fish, whales, dolphins, octopus, water hyacinth, hydrilla, lotus. The word is built on Latin aqua, water. The question says 'live on land', which is the other half of the same pair, so aquatic is precisely wrong rather than merely irrelevant.
• (d)Biotic — Half-true, and therefore the strongest distractor in the set. Plants and animals are indeed the biotic (living) components of a habitat — that is standard terminology. But biotic is defined against abiotic, i.e. living versus non-living; it does not distinguish land from water. Since the question specifies 'on land', the discriminating term is terrestrial. A student who stops at 'plants and animals are living, so biotic' has answered a question that was not asked.

A habitat is the place with its particular surroundings where an organism lives — where it finds food, shelter, protection and a place to breed. Habitats are classified first by medium into terrestrial (on land) and aquatic (in water), and then into finer types: terrestrial habitats include forests, grasslands, deserts, mountains and coastal regions, while aquatic habitats include freshwater bodies (ponds, lakes, rivers, streams) and marine ones (seas and oceans), with estuaries and marshes in between. Cutting across this classification is a second, entirely different axis: every habitat has biotic components (plants, animals, microorganisms) and abiotic components (air, water, soil, light, temperature). The examiner's whole design here is to see whether a candidate can keep the two axes apart.

Reason it in two steps. Step one: the question describes organisms, so any option naming a non-living category is out — that kills (a) Abiotic immediately. Step two: of the three survivors, ask which one uses the specific information given, namely 'on land'. 'Biotic' applies equally to land and water organisms, so it cannot be the discriminator; 'aquatic' is the wrong medium; 'terrestrial' is the one word that means land-dwelling. One point of wording: the booklet prints 'habitants' where standard usage would be 'habitats' (or 'inhabitants'), but the meaning — land-dwellers — is unambiguous and it does not affect the answer. Note also that UPPSC likes this family of vocabulary and returns to it: in 2023 it asked what desert-dwelling animals are called (xerocoles) and what a lotic ecosystem is (running water, i.e. rivers). Learn the habitat vocabulary as a set, not as isolated words.

• A habitat is the surroundings in which an organism lives; the two broad types are terrestrial (on land) and aquatic (in water).
• Terrestrial habitats include forests, grasslands, deserts, mountains and coastal areas; aquatic habitats include ponds, lakes, rivers, swamps, estuaries and oceans.
• Biotic components of a habitat are the living things — plants, animals, microorganisms; abiotic components are the non-living surroundings — air, water, soil, sunlight, temperature. Biotic/abiotic is a different axis from terrestrial/aquatic.
• Organisms are also named by the specific habitat they occupy: xerocoles (desert), arboreal (trees), fossorial (burrowing), aquatic (water) — the same naming habit UPPSC tested in 2023.
• Organisms show adaptations to their habitat: a cactus is a xerophyte with a fleshy stem, spines for leaves and deep roots for the desert; hydrilla is a hydrophyte with soft, ribbon-like submerged leaves; a camel and a fish are adapted respectively to terrestrial and aquatic life.

• Confusing the two axes. Biotic/abiotic separates living from non-living; terrestrial/aquatic separates land from water. A question that specifies the medium wants the second pair.
• Treating habitat and niche as synonyms. Habitat is the address; the ecological niche is the address plus the occupation — the organism's functional role in the community.
• Forgetting the in-between cases. Amphibians, mangroves and estuarine species straddle land and water, which is why exam items give a clean cue such as 'live on land'.

UPPSC asks this vocabulary as flat one-line NCERT recall — 'organisms living on land are called', 'desert dwelling animals are called', 'example of a lotic ecosystem' — while UPSC takes the same vocabulary a level up and tests the fine distinction, most clearly in its 2013 habitat-versus-niche question.

• practice — not a real PYQ

  Which one of the following is an abiotic component of a habitat?

  • (a)Earthworm
  • (b)Soil
  • (c)Fungi
  • (d)Algae

  Answer(b) Soil — abiotic means the non-living surroundings: air, water, soil, sunlight and temperature. Earthworms, fungi and algae are all living organisms and therefore biotic components.

• practice — not a real PYQ

  Animals that are adapted to live on trees are called :

  • (a)Fossorial animals
  • (b)Arboreal animals
  • (c)Xerocoles
  • (d)Aquatic animals

  Answer(b) Arboreal animals — from Latin arbor, tree; monkeys, langurs, squirrels and sloths are arboreal. Fossorial animals are burrowers (moles, rats), xerocoles are desert dwellers (camel, fennec fox) and aquatic animals live in water.