The UPSC Prelims 2025 question paper continued its legacy of being unpredictable, analytical, and concept-driven. With 100 questions in General Studies Paper I, the trend clearly reflected a balanced distribution across subjects like Polity, Economy, Environment, Science & Tech, History, and Geography. Among them, Environment & Ecology stood out with a total of 13 questions, constituting a significant portion and demanding focused preparation.
Overall Nature of UPSC Prelims 2025
This year, the paper appeared moderately tougher compared to the previous year. Questions across all subjects ranged from easy to medium and difficult levels, indicating a layered testing approach. The hallmark of this year's paper was its emphasis on core fundamentals, often intertwined with current affairs, reinforcing the need for integrated preparation.
Given below is the breakdown of the 100 questions asked in CSE Prelims 2025.
Environment & Ecology Section: Key Observations
The Environment & Ecology section in UPSC Prelims 2025 reflected a noticeable shift in focus. Rather than concentrating on static topics like species and ecological behavior, the paper leaned towards contemporary environmental issues and technological solutions. The questions tested both core concepts and awareness of current global challenges, particularly those linked to climate change and innovation.
Notable Themes Covered:
- Climate Change Mitigation Technologies – e.g., Direct Air Capture
- Artificial Weather Modification – e.g., Artificial Rainfall
- Sustainable Development and Climate Finance Mechanisms- e.g. Article 6 Paris Climate deal
The Detailed Analysis of UPSC Prelims 2025 Environment Section are as follows:
UPSC Prelims Environment & Ecology Q.
Consider the following:
I. Cigarette butts
II. Eyeglass lenses
III. Car tyres
How many of them contain plastic?
(a) Only one
(b) Only two
(c) All the three
(d) None
Answer: C
Explanation
- Option 1 is correct: Cigarette butts are a persistent form of toxic plastic pollution. Tobacco product waste also contains over 7000 toxic chemicals, including known human carcinogens. Cigarette filters are made of cellulose acetate and therefore also contribute significantly to plastic pollution.
- Option 2 is correct: Many eyeglass lenses are made of plastic. CR-39, also known as Columbia resin #39, is a common plastic material used in lenses. Other plastics like polycarbonate and Trivex are also used, each with its own properties. Plastic lenses offer advantages like being lightweight and less prone to shattering compared to traditional glass lenses.
- Option 3 is correct: Tyre particles are a significant but often-overlooked contributor to microplastic pollution. They account for 28% of microplastics entering the environment globally.
- Hence, option (c) is the correct answer.
MOTIVATION, SOURCES AND COVERAGE OF PRELIMS QUESTION IN THE VISIONIAS SOURCES
Motivation: Plastic Pollution is a major environmental issue often seen in the news. Nanoplastic pollution due to tyres was frequently seen in the news.
Sources:
Coverage of the topic in the VisionIAS Current Affairs Sources
- News Today (18 Nov 2024): New research reveals that microplastics in the atmosphere could be affecting weather and climate
Coverage of Topic in the VisionIAS All India Test Series/ Sandhan/Open Test
Sandhan VisionIAS Prelims Test Series Initiative
Q. Consider the following statements:
Statement I: Pollution from the tyres of vehicles is on the rise on account of increasing number of electric vehicles.
Statement II: Extra weight of electric vehicles, due to their batteries, leads to more abrasion releasing many toxic and carcinogenic chemicals such as 6PPD.
Which one of the following is correct in respect of the above statements?
(a) Both Statement I and Statement II are correct and Statement II is the correct explanation for Statement I.
(b) Both Statement I and Statement II are correct and Statement II is not the correct explanation for Statement I.
(c) Statement I is correct but Statement II is incorrect
(d) Statement I is incorrect but Statement II is correct
UPSC Prelims Environment & Ecology Q.
Consider the following substances:
I. Ethanol
II. Nitroglycerine
III. Urea
Coal gasification technology can be used in the production of how many of them?
(a) Only one
(b) Only two
(c) All the three
(d) None
Answer: B
Explanation
- Coal gasification is a process that converts coal into a gaseous fuel called syngas (synthesis gas), primarily composed of carbon monoxide (CO) and hydrogen (H2). This syngas can then be used as a fuel for various applications, including electricity generation, and as a feedstock for chemical production.
- Option 1 is correct: Syn Gas produced from Coal gasification can is usable in producing Synthetic Natural Gas (SNG), energy fuel (methanol & ethanol), ammonia for fertilizers and petro-chemicals. Synata Bio has designed an advanced syngas to ethanol technology to ferment syngas. The plant design includes utilization of unique and proprietary anaerobic microorganisms which provides higher hydrogen uptake and increases overall yield to ethanol. The production reactors produce a liquid product stream, “broth”, containing the dilute ethanol product (about 2.5%-3% w/v) in water that is distilled and dehydrated to produce the desired high purity thanol, prior to being sent to the finished product tanks.
- Option 3 is correct: Coal gasification based fertilizer plant at Talcher (Odisha): Talcher Fertilizer Ltd. (a joint venture of CIL, GAIL, RCF and FCIL) is engaged in setting up of an integrated coal gasification based urea plant wherein high ash coal from nearby Talcher coalfields blended with Pet-coke shall be utilized to produce 1.27 Million Metric Tonnes Per Annum (MMTPA) neemcoated Urea. Currently, construction activities are underway.
- Option 2 is not correct: Nitroglycerin, which was originally synthesized by Ascanio Sobrero, was used by Alfred Nobel to manufacture dynamite. It was in Nobel's dynamite factories in the late 1860s that the antianginal effect of nitroglycerin was discovered. Nitroglycerine, therefore, is a vasodilatory drug used primarily to provide relief from anginal chest pain. It is not produced using coal gasification. Hence, option (b) is the correct answer.
MOTIVATION, SOURCES AND COVERAGE OF PRELIMS QUESTION IN THE VISIONIAS SOURCES
Motivation: Coal Gasification is often seen in the news. Recently, Government of India approved two such projects in West Bengal and Odisha.
Sources:
Coverage of the topic in the VisionIAS Current Affairs Sources
- PT 365 2025 Environment: Article 4.4.6. Underground Coal Gasification (UCG)
- Monthly Current Affairs June 2024: Article 5.4. Underground Coal Gasification (UCG)
- News today (06 Feb 2025): Ministry of Coal announced applicants under Category-II of the Financial Incentive Scheme (FIS)
UPSC Prelims Environment & Ecology Q.
Consider the following statements:
Statement I: Activated carbon is a good and an attractive tool to remove pollutants from effluent streams and to remediate contaminants from various industries.
Statement II: Activated carbon exhibits a large surface area and a strong potential for adsorbing heavy metals.
Statement III: Activated carbon can be easily synthesized from environmental wastes with high carbon content.
Which one of the following is correct in respect of the above statements?
(a) Both statement II and Statement III are correct and both of them explain Statement I
(b) Both Statement II and Statement III are correct but only one of them explains Statement I
(c) Only one of the Statements II and III is correct and that explains Statement I
(d) Neither Statement II nor Statement III is correct.
Answer: A
Explanation
- Activated carbon is a popular and effective method for removing pollutants from water, particularly in wastewater treatment and industrial processes. Activated carbon is produced from environmental wastes with high carbon content. Lignocellulosic and coal materials have been used as raw materials planned for manufacturing of activated carbons. There are two approaches for preparing activated carbon that can be used in water purification processes: physical activation and chemical activation.
- Activated carbon has good potential for adsorbing heavy metals because of its greater surface area, microporous ability, and chemical complexity of its external area. Activated carbon can be made relatively easily at home using materials like coconut shells or wood and is therefore an attractive tool to remove pollutants.
- Hence, Both statement II and Statement III are correct and both of them explain Statement I.
MOTIVATION, SOURCES AND COVERAGE OF PRELIMS QUESTION IN THE VISIONIAS SOURCES
Motivation: Recently, a research team in Kerala has engineered activated carbon from coconut rachis.
Sources:
Coverage of Topic in the VisionIAS All India Test Series/ Sandhan/Open Test
Sandhan VisionIAS Prelims Test Series Initiative
Q. Which of the following are the uses of activated charcoal?
1. For curing drug overdose
2. Water filtration
3. Cheesemaking
4. Purifying air
Select the correct answer code given below.
(a) 1 and 3 only
(b) 2, 3 and 4 only
(c) 1, 2 and 4 only
(d) 1, 2, 3 and 4
UPSC Prelims Environment & Ecology Q.
Consider the following statements:
Statement I: Studies indicate that carbon dioxide emissions from cement industry account for more than 5% of global carbon emissions.
Statement II: Silica-bearing clay is mixed with limestone while manufacturing cement.
Statement III: Limestone is converted into lime during clinker production for cement manufacturing.
Which one of the following is correct in respect of the above statements?
(a) Both Statement II and Statement III are correct and both of them explain Statement I
(b) Both Statement II and Statement III are correct but only one of them explains Statement I
(c) Only one of the Statements II and III is correct and that explains Statement I
(d) Neither Statement II nor Statement III is correct
Answer: A
Explanation
- The high-temperature process for manufacturing cement, the all-important glue that binds the components of concrete, accounts for roughly 8% of the world’s anthropogenic carbon dioxide emissions and consumes 2–3% of the global energy supply, according to the International Energy Agency.
- The method calls for heating powdered limestone, a widely available, inexpensive material, and clay to roughly 1,450 °C in a kiln. The high-temperature process, known as calcination (clinker production), converts calcium carbonate (CaCO3), the principal component of limestone, to calcium oxide (CaO), or lime, releasing CO2. That simple reaction, which is key to making cement, is the source of about half the CO2 emissions in cement manufacturing.
- Also, mixing silica-based clay with limestone during cement production leads to the release of CO2. This occurs because there is use of energy for this process and it releases CO2 gas. Hence, Both Statement II and Statement III are correct and both of them explain Statement I.
MOTIVATION, SOURCES AND COVERAGE OF PRELIMS QUESTION IN THE VISIONIAS SOURCES
Motivation: Industries with high CO2 emissions are an important topic under Global Warming.
Sources:
Coverage of the topic in the VisionIAS Current Affairs Sources
- News today (24 May 2024): Zero Carbon Cement
The remaining Environment & Ecology questions from UPSC Prelims 2025 are discussed in - Part 2 of the series.
VisionIAS Faculty Discussion: Environment & Ecology Section Analysis of UPSC Prelims 2025
To help aspirants decode the evolving pattern and approach of UPSC Prelims 2025, our expert faculty at VisionIAS has conducted a detailed analysis session, focusing on the trends, difficulty level, question framing, and effective strategies for future preparation. This video not only breaks down theEnvironment & Ecology but also offers valuable insights on elimination techniques, source mapping, and topic prioritization for UPSC Prelims 2026.
To watch the CSE Prelims 2025 Analysis Video, click on the following link:
UPSC Prelims 2025 | GS Paper 1 | Analysis & Discussion I Geography - Environment
Prepare Smarter with VisionIAS: 10-Year PYQ Environment & Ecology Compilation
To help aspirants systematically decode trends, VisionIAS has released a comprehensive compilation of last 10 years’ Environment & Ecology PYQs (2015–2024). This document offers:
- Topic-wise categorization
- Difficulty level analysis
- Source identification
- Elimination strategies
- Micro-level sub-topic mapping
- Current affairs integration guide
Link to read and download the document: 10 year UPSC PYQ Trend Analysis : Environment
Our faculty at VisionIAS has conducted an insightful discussion on the Environment & Ecology PYQ Trend Analysis Document. This session covers key patterns, conceptual depth of questions, and strategies to tackle future Prelims papers more effectively. The discussion also highlights how our 10-year PYQ document can be used as a powerful tool for focused preparation.
To watch the discussion by our faculty, click on the link below: GS Prelims | 10 Year PYQ (2015 - 2024) | Environment - Part 1
Further, understand the UPSC Prelims with VisionIAS's Master Classes on PYQ of UPSC Prelims. This program transforms 13 years of UPSC previous year question papers into a powerful strategy- building resource. Designed to enhance your accuracy, speed, and conceptual clarity, it's a smart way to turn UPSC PYQs into your strongest preparation tool