Geography & Environment · Environment & Ecology

Ecology & Ecosystems: 30 previous year questions

UPSC has asked 30 questions on Ecology & Ecosystems between 2002 and 2026: CAPF 18 · CDS 5 · CISF (LDCE) 3 · Geo-Scientist 2 · NDA 1 · CSE 1. 24 of them came after 2015, so this is a live topic examiners keep returning to. 1 were set in Civil Services Prelims; the rest come from UPSC's other papers, which draw on the same question bank.

Practise these 30, one at a time Read the questions

Tap an option to check yourself. Answers follow the official UPSC key; where the key was dropped or disputed the question is not shown.

CAPF2026Ecology & Ecosystems On card ENV 1·2

Which of the following statements about eutrophication is/are correct? 1. Eutrophication takes place in young lakes when the water is cold and clear. 2. Eutrophication is caused by nutrient enrichment in water bodies. Select the answer using the code given below.

Show answer

Answer B (official UPSC key)Eutrophication is caused by nutrient enrichment in water bodies | NOT: eutrophication in young cold clear lakes; it typically occurs in older lakes, young lakes are oligotrophic (nutrient-poor, cold, clear)

CISF (LDCE)2025Ecology & Ecosystems On card ENV 1·1

Which one of the following is the habitat for the Great Indian Bustard?

Show answer

Answer B (official UPSC key)Great Indian Bustard (Ardeotis nigriceps) habitat: arid ecosystem (dry grassland and scrubland) | Primary stronghold: Thar Desert (Desert National Park, Rajasthan)

CAPF2024Ecology & Ecosystems On card ENV 1·1

In an ecosystem why is the number of trophic levels of a food chain usually limited ?

Show answer

Answer B (official UPSC key)Number of trophic levels in a food chain is limited because of the loss of energy at each trophic level | About 10% of energy passes to the next level (10% rule)

CISF (LDCE)2024Ecology & Ecosystems On card ENV 1·1

Ecotone is a

Show answer

Answer B (official UPSC key)Ecotone is a transitional ecosystem between two different ecosystems, often with high biodiversity

Geo-Scientist2023Ecology & Ecosystems On card ENV 1·2

In deep ponds and lakes, which one of the following vertical zones receives least light penetration?

Show answer

Answer D (official UPSC key)Profundal zone receives the least light penetration in deep ponds and lakes (deepest part, below the limnetic zone; no photosynthesis)

NDA2023 · 1Ecology & Ecosystems On card ENV 1·1

Organisms capable of using CO₂ as principal carbon source are called:

Show answer

Answer A (official UPSC key)Autotrophs use CO₂ as their principal carbon source (photosynthesis or chemosynthesis) | Heterotrophs depend on organic carbon sources

CAPF2022Ecology & Ecosystems On card ENV 1·1

"The boundary layer of the forest at which the energy exchange occurs and some insolation is returned directly to space is

Show answer

Answer C (official UPSC key)Forest canopy: boundary layer of the forest where energy exchange occurs and some insolation is returned directly to space

CAPF2022Ecology & Ecosystems On card ENV 1·1

"The organisms that prefer high salt concentration habitats refer to as

Show answer

Answer C (official UPSC key)Halophiles: organisms that prefer high salt concentration habitats (e.g., brine shrimp) | Alkaliphiles tolerate high alkaline pH (above 9)

CAPF2022Ecology & Ecosystems On card ENV 1·1

The World Wetland Day is celebrated on which one of the following dates every year?

Show answer

Answer D (official UPSC key)World Wetlands Day is celebrated on 2 February every year (marks adoption of the Ramsar Convention) | UNGA Resolution 75/317 (30 August 2021) established it

CDS2022 · 1Ecology & Ecosystems On card ENV 1·2

Which of the following is/are the function(s) of environment ? 1. Supplying resources 2. Sustaining life 3. Providing aesthetic services Select the correct answer using the code given below :

Show answer

Answer D (official UPSC key)Functions of environment: supplying resources; providing aesthetic services

CDS2021 · 2Ecology & Ecosystems On card ENV 1·1

Which of the following limits the number of trophic levels in a food chain ?

Show answer

Answer C (official UPSC key)Number of trophic levels in a food chain is limited by decreasing available energy at higher trophic levels | Only about 10% of energy passes to the next level (10% law)

CDS2021 · 2Ecology & Ecosystems On card ENV 1·1

While studying vegetation of an area, terms like ‗population‘ and ‗community‘ are often used. Which one of the following statements best describes a population ?

Show answer

Answer A (official UPSC key)Population: a group of organisms of one species living in the same area

CISF (LDCE)2021Ecology & Ecosystems On card ENV 1·1

The idea of Ecological Succession was first formally coined by

Show answer

Answer B (official UPSC key)Idea of ecological succession was first formally developed by Frederic E. Clements (book 'Plant Succession', 1916) | Succession leads to a stable climax community

Geo-Scientist2021Ecology & Ecosystems On card ENV 1·1

A growing population cannot increase indefinitely at a geometric rate because a given habitat has a carrying capacity. This type of growth is known as:

Show answer

Answer C (official UPSC key)Logistic growth: population growth that slows as it approaches the carrying capacity (K), forming an S-shaped (sigmoid) curve

CAPF2020Ecology & Ecosystems On card ENV 1·1

Transition zone of varied natural vegetation occupying the boundary between two adjacent and differing plant communities is known as

Show answer

Answer B (official UPSC key)Ecotone: transition zone between two adjacent and differing plant communities

CAPF2020Ecology & Ecosystems On card ENV 1·2

Which one of the following statements about the Acacia tree is/are correct ? 1. It has a long shallow root system which enables it to find moisture 2. It has thorny leaves to prevent water loss 3. It has wide crown so the foliage can absorb the maximum Sunlight Select the correct answer using the code given below:

Show answer

Answer D (official UPSC key)Acacia tree (per key): long shallow root system to find moisture; thorny leaves to prevent water loss; wide crown so foliage absorbs maximum sunlight

CDS2020 · 1Ecology & Ecosystems On card ENV 1·1

Geomorphic factors influencing plant and animal distributions are

Show answer

Answer C (official UPSC key)Geomorphic factors influencing plant and animal distribution: slope angle, slope aspect and relief

CAPF2019Ecology & Ecosystems On card ENV 1·2

Phreatophytes are the plants adapted to grow in

Show answer

Answer C (official UPSC key)Phreatophytes: deep-rooted plants of arid environments that draw water from the phreatic zone below the water table (e.g., Mesquite, Greasewood)

CDS2019 · 2Ecology & Ecosystems On card ENV 1·1

Which one of the following is the correct sequential phase in the successional development of vegetation community in a habitat ?

Show answer

Answer C (official UPSC key)Sequence of vegetation succession: Nudation -> Migration -> Reaction -> Stabilization

CAPF2017Ecology & Ecosystems On card ENV 1·2

NPP (Net Primary Productivity) is highest for

Show answer

Answer A (official UPSC key)Net Primary Productivity (NPP) is highest for tropical forests (of: tropical forests, swamps, reefs, woodland and shrubland)

CAPF2017Ecology & Ecosystems On card ENV 1·1

Study of a single species and the environmental factors in its habitat is called

Show answer

Answer C (official UPSC key)Autecology: study of a single species and the environmental factors in its habitat | Synecology: structure, development and distribution of ecological communities

CAPF2017Ecology & Ecosystems On card ENV 1·1

The ecological niche of an organism relates to

Show answer

Answer A (official UPSC key)Ecological niche of an organism relates to its specific habitat (per key)

CAPF2017Ecology & Ecosystems On card ENV 1·2

Free swimming macroscopic animals in an aquatic environment are referred to as

Show answer

Answer D (official UPSC key)Nekton: free-swimming macroscopic animals in an aquatic environment | Plankton: drift with currents, usually microscopic

CAPF2017Ecology & Ecosystems On card ENV 1·1

The term Bio-magnifications is referred to as

Show answer

Answer C (official UPSC key)Biomagnification: accumulation of increasing amounts of non-degradable pollutants in organisms up the food chain

CAPF2012Ecology & Ecosystems On card ENV 1·2

Consider the following statements : 1. Creepers or climbers are commonly found in the tropical rain forest. 2. The epiphytes, which do not have their roots on the ground, survive on the trees in the tropical rain forest. 3. All epiphytes are not creepers. Which of the statements given above is/are correct?

Show answer

Answer A (official UPSC key)Creepers or climbers are common in tropical rain forests | Epiphytes have no roots on the ground and survive on trees in tropical rain forests | Not all epiphytes are creepers

CAPF2012Ecology & Ecosystems On card ENV 1·2

How do marine animals survive in water without air contact?

Show answer

Answer B (official UPSC key)Marine animals survive without air contact by taking dissolved oxygen from water (gills in fish and crabs; skin in some soft-bodied creatures) | Marine mammals like whales and dolphins surface to breathe air with lungs

CAPF2011Ecology & Ecosystems On card ENV 1·1

Which one among the following phenomena includes processes, such as production, predation, nutrient transformation, and the influx and efflux of energy and materials ?

Show answer

Answer B (official UPSC key)Ecosystem function includes production, predation, nutrient transformation and the influx and efflux of energy and materials

CAPF2010Ecology & Ecosystems On card ENV 1·2

Plants that behave as a Xerophyte in one season and as hydrophyte in another season is known as :

Show answer

Answer B (official UPSC key)Tropophytes: plants that behave as xerophytes in one season and as hydrophytes in another (seasonal climate)

CAPF2009Ecology & Ecosystems On card ENV 1·2

Aquatic animals breathe much faster than terrestrial animals because of :

Show answer

Answer A (official UPSC key)Aquatic animals breathe faster than terrestrial animals because of the low amount of dissolved oxygen in water (oxygen in air is much higher)

CSE2002Ecology & Ecosystems On card ENV 1·1

Consider the following ecosystems: 1. Taiga 2. Tropical Evergreen 3. Tropical Deciduous 4. Tundra The correct sequence in decreasing order of the Albedo values of these ecosystems is:

Show answer

Answer B (official UPSC key)Albedo in decreasing order: Tundra > Taiga > Tropical Deciduous > Tropical Evergreen | Tundra highest due to snow and ice cover