UPSC Prelims 2013
Environment & Ecology Previous Year Questions (PYQs)
Explore 21 solved UPSC Prelims 2013 Environment & Ecology questions with detailed step-by-step bilingual solutions, option analysis, and answer keys.
Consider the following animals:
- Sea cow
- Sea horse
- Sea lion
Which of the above is/are mammal/mammals?
Detailed Explanation:
Sea Cow (Dugong): A herbivorous marine mammal found in coastal waters of the Indian and Pacific Oceans; classified under class Mammalia.
Sea Horse: A carnivorous fish (not a mammal) belonging to class Osteichthyes; found in shallow tropical and temperate waters.
Sea Lion: A carnivorous marine mammal of family Otariidae; breeds on Pacific and Atlantic coasts; classified under class Mammalia.
Therefore, only Sea Cow (1) and Sea Lion (3) are mammals.
Mycorrhizal Biotechnology has been used in rehabilitating degraded sites because mycorrhiza enables the plants to -
- Resist drought and increase absorptive area
- Tolerate extremes of pH
- Resist disease infestation
Select the correct answer using the codes given below:
Detailed Explanation:
✅ Statement 1 – Correct: Mycorrhizal fungi form symbiotic associations with plant roots, greatly increasing the effective absorptive surface area (fungal hyphae extend beyond roots) and improving water uptake, enabling plants to resist drought stress.
✅ Statement 2 – Correct: Mycorrhizae help plants tolerate extreme pH conditions (both acidic and alkaline soils) by facilitating nutrient acquisition even when pH levels reduce nutrient availability.
✅ Statement 3 – Correct: Mycorrhizae provide bioprotection against disease infestation by competing with soil-borne pathogens, producing antimicrobial compounds, and enhancing plant immune responses.
With reference to food chains in ecosystems, consider the following statements :
- A food chain illustrates the order in which a chain of organisms feeds upon each other.
- Food chains are found within the populations of a species.
- A food chain illustrates the numbers of each organism which are eaten by others.
Which of the statements given above is/are correct?
Detailed Explanation:
✅ Statement 1 – Correct: A food chain illustrates the linear sequence in which organisms feed upon each other, showing the order of energy flow from producers → primary consumers → secondary consumers → tertiary consumers.
❌ Statement 2 – Incorrect: Food chains operate between different species, not within populations of a single species; they represent inter-species feeding relationships across different trophic levels.
❌ Statement 3 – Incorrect: A food chain shows only the feeding relationship and direction of energy flow, not the numbers or biomass of organisms; ecological pyramids illustrate numerical or biomass relationships.
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In the grasslands, trees do not replace the grasses as a part of an ecological succession because of
Detailed Explanation:
Grasslands maintain themselves as climax communities due to two primary limiting factors: water scarcity and periodic fires.
Grasses have meristematic tissue at the base (not tips), allowing rapid regrowth after fire, while tree seedlings die in fires. Additionally, low annual precipitation (25-75 cm) and thin, dry soil prevent tree establishment, maintaining grasslands in a sub-climax stage.
Which of the following can be found as pollutants in the drinking water in some parts of India?
- Arsenic
- Sorbitol
- Fluoride
- Formaldehyde
- Uranium
Select the correct answer using the codes given below.
Detailed Explanation:
✅ Arsenic (1) – Correct: Found in groundwater of West Bengal, Bihar, Uttar Pradesh, Assam, Jharkhand due to natural leaching from arsenic-bearing rocks; causes arsenicosis and skin lesions.
❌ Sorbitol (2) – Incorrect: A sugar alcohol used as artificial sweetener and humectant; not a naturally occurring groundwater pollutant in India.
✅ Fluoride (3) – Correct: Endemic in Rajasthan, Andhra Pradesh, Tamil Nadu, Gujarat, Haryana and other states; causes dental and skeletal fluorosis from geological sources.
❌ Formaldehyde (4) – Incorrect: An industrial chemical and disinfectant; not a common groundwater contaminant in Indian drinking water systems.
✅ Uranium (5) – Correct: Detected in groundwater of Punjab, Rajasthan, Haryana and parts of southern India; leaches from uranium-bearing granitic rocks.
With reference to the food chains in ecosystems, which of the following kinds of an organism is/are known as decomposer organism/organisms?
- Virus
- Fungi
- Bacteria
Select the correct answer using the codes given below.
Detailed Explanation:
Fungi and Bacteria are the primary decomposers in ecosystems that break down dead organic matter into simpler inorganic substances, recycling nutrients back into the environment.
Viruses are not decomposers—they are metabolically inactive outside host cells and function as obligate intracellular parasites that require living cells to replicate, playing no role in decomposition.
Photochemical smog is a resultant of the reaction among -
Detailed Explanation:
Photochemical smog is formed when nitrogen dioxide (NO₂), volatile organic compounds (VOCs), and oxygen react in the presence of sunlight to produce ozone (O₃) and peroxyacetyl nitrate (PAN).
Option 1 correctly identifies the resultant components (NO₂, O₃, and PAN) that characterize photochemical smog, which forms through photochemical reactions triggered by ultraviolet (UV) sunlight.
Acid rain is caused by the pollution of the environment by -
Detailed Explanation:
Acid rain is caused by sulphur dioxide (SO₂) and nitrogen oxides (NOₓ) released from burning fossil fuels and vehicle emissions.
These gases react with water vapor, oxygen, and other atmospheric chemicals to form sulphuric acid (H₂SO₄) and nitric acid (HNO₃), which fall as acid rain.
Which of the following adds/add nitrogen to the soil?
- Excretion of urea by animals
- Burning of coal by man
- Death of vegetation
Select the correct answer using the codes given below.
Detailed Explanation:
✅ Statement 1 – Correct: Urea (CO(NH₂)₂) excreted by animals is decomposed by soil microbes into ammonia, which is further converted into nitrates and nitrites, adding nitrogen to soil.
❌ Statement 2 – Incorrect: Burning of coal releases nitrogen oxides (NOₓ) into the atmosphere, not directly into soil; these contribute to air pollution and acid rain.
✅ Statement 3 – Correct: Death of vegetation leads to decomposition by bacteria and fungi, which breaks down organic matter and releases nitrogen compounds back into soil.
Due to improper/indiscriminate disposal of old and used computers or their parts, which of the following are released into the environment as e-waste?
- Beryllium
- Cadmium
- Chromium
- Heptachlor
- Mercury
- Lead
- Plutonium
Select the correct answer using the codes given below.
Detailed Explanation:
E-waste from computers contains heavy metals used in electronic components: Beryllium (motherboards, connectors), Cadmium (rechargeable batteries, circuit boards), Chromium (corrosion protection in steel plates), Mercury (fluorescent lamps, switches), and Lead (solder, CRT monitors).
Heptachlor is an organochlorine insecticide, not used in electronics, and Plutonium is a radioactive element found only in nuclear applications, not in computers.
Which one of the following terms describes not only the physical space occupied by an organism but also its functional role in the community of organisms?
Detailed Explanation:
Ecological niche describes both the physical space occupied by an organism and its functional role in the community, including its interactions with biotic and abiotic factors.
Habitat refers only to the physical location where an organism lives, while ecotone is a transition zone between two ecosystems, and home range is the area an animal travels during normal activities.
In which of the following States is lion-tailed macaque found in its natural habitat?
- Tamil Nadu
- Kerala
- Karnataka
- Andhra Pradesh
Select the correct answer using the codes given below.
Detailed Explanation:
✅ Statement 1 – Correct: Lion-tailed macaque is found in Tamil Nadu's Western Ghats forests, particularly in Anaimalai Hills and surrounding evergreen regions.
✅ Statement 2 – Correct: Kerala hosts significant populations in Silent Valley National Park and other Western Ghats rainforests.
✅ Statement 3 – Correct: Karnataka's Western Ghats regions including Kudremukh and Sirsi-Honnavara ranges form part of the natural habitat.
❌ Statement 4 – Incorrect: Andhra Pradesh lies outside the Western Ghats endemic zone; the species is not found naturally in this state.
Which one of the following is the correct sequence of ecosystems in the order of decreasing productivity?
Detailed Explanation:
Ecosystems ranked by Net Primary Productivity (NPP) from highest to lowest:
Mangroves (high NPP) – receive nutrient inputs from both terrestrial runoff and tidal flushing, warm tropical climate, high photosynthetic rates
Grasslands (moderate NPP) – abundant herbaceous vegetation with productivity dependent on rainfall, soil fertility, and grazing intensity
Lakes (moderate to low NPP) – productivity varies with nutrient status (eutrophic > oligotrophic), generally lower than terrestrial ecosystems
Oceans (lowest NPP) – particularly open ocean zones have limited nutrient availability in photic zones, lowest productivity despite covering largest area
Consider the following organisms:
- Agaricus
- Nostoc
- Spirogyra
Which of the above is/are used as biofertilizer/biofertilizers?
Detailed Explanation:
Nostoc is a nitrogen-fixing cyanobacterium (blue-green algae) used as a biofertilizer due to its ability to fix atmospheric nitrogen and enrich soil.
Agaricus is a mushroom (fungus) used for food, not as a biofertilizer.
Spirogyra is a green alga (filamentous) used for research and education, not as a biofertilizer.
Consider the following pairs about parks and rivers passing through them:
- Corbett National Park: Ganga
- Kaziranga National Park: Manas
- Silent Valley National Park: Kaveri
Which of the above pairs is/are correctly matched?
Detailed Explanation:
❌ Pair 1 – Incorrect: Ramganga River (not Ganga) flows through Corbett National Park, Uttarakhand.
❌ Pair 2 – Incorrect: Brahmaputra River (not Manas) flows through Kaziranga National Park, Assam. Manas is a separate river flowing through Manas National Park.
❌ Pair 3 – Incorrect: Kunthipuzha River (not Kaveri) flows through Silent Valley National Park, Kerala.
Consider the following:
- Star tortoise
- Monitor lizard
- Pygmy Hog
- Spider monkey
Which of the above are found in India?
Detailed Explanation:
✅ Star Tortoise – Found in India: Native to dry scrub forests of south and west India, listed as Vulnerable on IUCN Red List.
✅ Monitor Lizard – Found in India: Four species (Bengal Monitor, Water Monitor, Desert Monitor, Yellow Monitor) protected under Schedule I of Wildlife Protection Act, 1972.
✅ Pygmy Hog – Found in India: World's smallest and rarest wild pig, now restricted to Manas National Park, Assam, listed as Critically Endangered.
❌ Spider Monkey – Not Found in India: New World monkey native to Central and South America (southern Mexico to Brazil), absent from Indian wildlife.
Consider the following pairs:
| Protected areas | Region |
|---|---|
| 1. Nokrek Biosphere Reserve | Garo Hills |
| 2. Logtak (Loktak) Lake | Barail Range |
| 3. Namdapha National Park | Dafla Hills |
Which of the above pairs is/are correctly matched?
Detailed Explanation:
✅ Pair 1 – Correct: Nokrek Biosphere Reserve is located in the Garo Hills of Meghalaya, known for conserving citrus gene pool.
❌ Pair 2 – Incorrect: Loktak Lake is located in Manipur valley (not Barail Range), famous for Keibul Lamjao National Park with floating phumdis.
❌ Pair 3 – Incorrect: Namdapha National Park is in Changlang district of Arunachal Pradesh near Myanmar border (not in Dafla Hills, which are in central Arunachal).
Consider the following fauna of India:
- Gharial
- Leatherback turtle
- Swamp deer
Which of the above is/are endangered?
Detailed Explanation:
✅ Gharial (Gavialis gangeticus) – Listed as Critically Endangered (CR) on IUCN Red List; faces drastic population decline due to habitat loss, prey depletion, and fishing nets.
✅ Leatherback turtle (Dermochelys coriacea) – Categorized as Vulnerable (VU) globally; found in Andaman & Nicobar Islands; protected under Schedule I, Wildlife Protection Act, 1972.
✅ Swamp deer/Barasingha (Rucervus duvaucelii) – Listed as Vulnerable (VU) on IUCN Red List; threatened by habitat fragmentation and grassland conversion.
All three species fall under IUCN 'Threatened' categories (CR/EN/VU) and are considered endangered in broader conservation context.
Contour bunding is a method of soil conservation used in
Detailed Explanation:
Contour bunding is a soil and water conservation technique used on sloping lands (typically 2-10% gradient) where earthen embankments are constructed along contour lines to reduce water runoff velocity and prevent soil erosion.
It is primarily employed in rainfed agricultural areas on gentle to moderate slopes, not in desert margins (where wind breaks are used), flat plains (where leveling/drainage is needed), or scrublands (where weed control is unrelated to contour structures).
Which one among the following industries is the maximum consumer of water in India?
Detailed Explanation:
Thermal power plants are the maximum consumers of industrial water in India, accounting for approximately 88% of annual industrial water consumption.
Engineering (~5%), Paper & Pulp (~2.3%), and Textiles (~2%) industries consume significantly smaller shares of industrial water, making thermal power the clear frontrunner in industrial water usage.
Showing 1 to 20 of 21 questions
UPSC Prelims 2013 - Environment & Ecology Chapter-wise Distribution
Biodiversity and Conservation
7 Qs (33.3%)Fundamentals of Ecology
6 Qs (28.6%)Environmental Pollution
4 Qs (19%)Flora, Fauna and Protected Areas
2 Qs (9.5%)Environmental Issues & Challenges
1 Qs (4.8%)Natural Resources & Conservation
1 Qs (4.8%)UPSC Prelims 2013 - Environment & Ecology Questions FAQs
Q1 How many Environment & Ecology questions were asked in UPSC Prelims 2013?
Q2 What is the chapter-wise question distribution for Environment & Ecology in UPSC Prelims 2013?
- Biodiversity and Conservation: 7 questions (33.3%)
- Fundamentals of Ecology: 6 questions (28.6%)
- Environmental Pollution: 4 questions (19%)
- Flora, Fauna and Protected Areas: 2 questions (9.5%)
- Environmental Issues & Challenges: 1 questions (4.8%)
- Natural Resources & Conservation: 1 questions (4.8%)