UPSC Civil Services Examination Science, Technology and Environment Syllabus

What does India's Agni series and BrahMos missile represent?

The Agni series are India's indigenous nuclear-capable surface-to-surface ballistic missiles of increasing range (Agni-I to Agni-V, intercontinental). BrahMos is a supersonic cruise missile developed jointly by India and Russia.

What is the difference between nuclear fission and nuclear fusion?

Fission is the splitting of a heavy nucleus (e.g., Uranium-235) into lighter nuclei, releasing energy; it powers current reactors and atomic bombs. Fusion is the joining of light nuclei (e.g., hydrogen isotopes) into a heavier one, releasing more energy; it powers the Sun and hydrogen bombs.

What are the three stages of India's nuclear power programme and the key fuel of each?

Stage 1: Pressurised Heavy Water Reactors using natural uranium (producing plutonium). Stage 2: Fast Breeder Reactors using plutonium with a thorium blanket. Stage 3: reactors using Uranium-233 bred from India's abundant thorium reserves.

Why is thorium especially important for India's nuclear strategy?

India holds among the world's largest thorium reserves (notably in Kerala's monazite sands) but limited uranium, so the long-term goal is a self-reliant thorium-based fuel cycle in the third stage of its nuclear programme.

What do the computing terms 'bit' and 'byte' mean, and how many bits make a byte?

A bit is the smallest unit of data, a single binary digit (0 or 1). A byte is a group of 8 bits, the standard unit for representing one character of data.

What is the difference between IPv4 and IPv6 addresses?

IPv4 uses 32-bit addresses (about 4.3 billion addresses, e.g., 192.168.0.1). IPv6 uses 128-bit addresses (a vastly larger pool, written in hexadecimal), introduced to overcome IPv4 exhaustion.

Define artificial intelligence, machine learning, and deep learning and their relationship.

AI is the broad field of machines performing tasks needing human-like intelligence. Machine learning is a subset where systems learn patterns from data without explicit programming. Deep learning is a subset of ML using multi-layered neural networks. (Deep learning is within ML, which is within AI.)

What is blockchain, and what is its core defining feature?

Blockchain is a distributed, decentralised digital ledger in which records (blocks) are cryptographically linked in a chain across many computers. Its core feature is tamper-resistance/immutability: once recorded, data cannot easily be altered.

What is the difference between PCR and recombinant DNA technology in biotechnology?

PCR (Polymerase Chain Reaction) amplifies (makes many copies of) a specific DNA segment for detection/analysis. Recombinant DNA technology involves cutting and joining DNA from different sources (using restriction enzymes and vectors) to create new genetic combinations, e.g., for insulin production.

What are GMOs, and name one well-known genetically modified crop relevant to India.

GMOs (Genetically Modified Organisms) have DNA altered through genetic engineering for desired traits. Bt cotton, carrying a Bacillus thuringiensis gene for pest resistance, is the main commercially approved GM crop in India.

What is CRISPR-Cas9 used for in biotechnology?

CRISPR-Cas9 is a precise, low-cost gene-editing tool that uses a guide RNA and the Cas9 enzyme to cut DNA at a targeted site, allowing genes to be added, removed, or altered for research, agriculture, and gene therapy.

What is the difference between a vaccine and an antibiotic?

A vaccine is a preventive agent that trains the immune system (using weakened/inactivated pathogens or antigens) to fight a future infection. An antibiotic is a curative drug that kills or inhibits bacteria in an existing infection; it does not work on viruses.

What are the main types/platforms of vaccines? Give an example of each.

Live attenuated (e.g., BCG, MMR), inactivated/killed (e.g., Covaxin, polio IPV), subunit/protein, toxoid (e.g., tetanus), and mRNA/nucleic-acid vaccines (e.g., Pfizer, Moderna COVID-19).

What is the difference between generic and patented (branded) medicines?

A patented/branded drug is sold exclusively by the originator company during patent protection. A generic medicine is the same active ingredient sold after patent expiry by other manufacturers, typically far cheaper. India is a leading global supplier of generics ('pharmacy of the world').

What is nanotechnology, and what is the size range that defines the nanoscale?

Nanotechnology is the manipulation of matter at the atomic/molecular scale to exploit novel properties. The nanoscale is 1 to 100 nanometres (1 nm = one billionth of a metre).

What are the three classes of robots based on autonomy and degree of human control?

Pre-programmed/automated robots (fixed repetitive tasks), teleoperated/remote-controlled robots (human-guided in real time), and autonomous robots (operate independently using sensors and AI). Some classifications add humanoid and augmenting robots.

Name two important Indian R&D / indigenisation initiatives and their focus.

Examples: Make in India and Atmanirbhar Bharat (self-reliance in manufacturing/defence), DRDO (defence research), CSIR (industrial/scientific research), and the defence 'positive indigenisation lists' restricting imports of specified items to boost domestic production.

What is an ecosystem, and what are its two broad components?

An ecosystem is a community of living organisms interacting with each other and their physical environment as a functional unit. Its two components are biotic (living: producers, consumers, decomposers) and abiotic (non-living: soil, water, air, sunlight, temperature).

Distinguish between a food chain and a food web, and what is a trophic level?

A food chain is a single linear sequence of who eats whom (producer to top consumer). A food web is the interconnected network of many overlapping food chains. A trophic level is each feeding step (producers, primary consumers, etc.) in that transfer of energy.

What are biodiversity hotspots, and how many are recognised in India?

Biodiversity hotspots are regions with exceptionally high species richness and high endemism that are severely threatened. India has four: the Himalayas, the Western Ghats, the Indo-Burma region, and Sundaland (Nicobar Islands).

What is the '10 percent law' of energy flow in ecosystems (Lindeman's law)?

Only about 10% of the energy at one trophic level is transferred to the next; the remaining ~90% is lost mainly as heat in metabolism. This limits the number of trophic levels in a food chain.

What are the primary air pollutants responsible for acid rain, and what is its main effect?

Sulphur dioxide (SO2) and nitrogen oxides (NOx) form sulphuric and nitric acids in the atmosphere. Acid rain (pH below ~5.6) damages forests, acidifies soils and lakes, and corrodes buildings/monuments (e.g., marble of the Taj Mahal).

What is eutrophication, and what causes it?

Eutrophication is the over-enrichment of a water body with nutrients (especially nitrogen and phosphorus from fertiliser/sewage runoff), causing algal blooms that deplete dissolved oxygen and kill aquatic life.

What do the air-quality terms PM2.5 and PM10 refer to, and why is PM2.5 more dangerous?

They are particulate matter with diameters of 2.5 micrometres and 10 micrometres or less. PM2.5 is more dangerous because the finer particles penetrate deep into the lungs and enter the bloodstream, causing serious respiratory and cardiovascular harm.

What is the difference between in-situ and ex-situ conservation? Give an example of each.

In-situ conservation protects species in their natural habitat (e.g., national parks, wildlife sanctuaries, biosphere reserves). Ex-situ conservation protects species outside their natural habitat (e.g., zoos, botanical gardens, gene/seed banks).

Differentiate between a national park, a wildlife sanctuary, and a biosphere reserve in India.

National park: highly protected area for ecosystems, no human activity/grazing allowed. Wildlife sanctuary: protects specific species, some regulated human activity permitted. Biosphere reserve: large area with a core (strict protection), buffer, and transition zone balancing conservation and sustainable use.

Name two flagship species-conservation projects in India and the animal each targets.

Project Tiger (1973, conserving the Bengal tiger and its habitat) and Project Elephant (1992, conserving Asian elephants and their corridors). Others include the Crocodile and Vulture conservation projects.

What is the greenhouse effect, and name the major greenhouse gases.

The greenhouse effect is the trapping of outgoing infrared heat by atmospheric gases, warming the Earth. Major greenhouse gases: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), water vapour, and fluorinated gases/CFCs.

What are the Paris Agreement's main temperature goal and the concept of 'net zero'?

The Paris Agreement (2015) aims to limit global warming to well below 2 degrees C, preferably 1.5 degrees C, above pre-industrial levels. 'Net zero' means balancing emitted greenhouse gases with an equal amount removed from the atmosphere; India targets net zero by 2070.

What is the difference between a natural and a man-made (anthropogenic) disaster? Give two examples of each.

Natural disasters arise from natural processes (e.g., earthquakes, floods, cyclones, tsunamis). Man-made/anthropogenic disasters result from human activity (e.g., industrial/chemical accidents like Bhopal gas tragedy, oil spills, nuclear accidents).

Define hazard, vulnerability, and risk in disaster management, including the risk relationship.

A hazard is a potentially damaging event/phenomenon. Vulnerability is the susceptibility of a community/asset to harm. Risk is the expected loss, broadly Risk = Hazard x Vulnerability x Exposure (divided by capacity to cope).