Biology, health and biotechnology: previous-year questions
68 real UPSC Prelims questions (2011–2026) with the official answer and a clear explanation. 12 of them came in the last five papers.
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With reference to Neem tree, consider the following statements :
- 1. Neem oil can be used as a pesticide to control the proliferation of some species of insects and mites.
- 2. Neem seeds are used in the manufacture of biofuels and hospital detergents.
- 3. Neem oil has applications in pharmaceutical industry.
Which of the statements given above is/are correct?
Answer (c) & explanation
Azadirachtin in neem oil repels insects and disrupts their growth, so neem-based products control many insects and mites (1 correct). Neem oil is also used in the pharmaceutical industry, as well as in soaps and toothpastes (3 correct). UPSC's key does not accept statement 2 on biofuels and hospital detergents, so the answer is (c).
India made neem-coated urea compulsory in 2015: the coating slows nitrogen release and stopped urea from being diverted to industry. Neem was also at the centre of a famous biopiracy case, in which a European patent on a neem fungicide was revoked. Notice how traditional knowledge links to IPR.
Answer as per the official UPSC answer key.
Which one of the following is the process involved in photosynthesis?
Answer (b) & explanation
Photosynthesis captures light energy (free energy) and stores it as chemical potential energy in glucose made from carbon dioxide and water, releasing oxygen (b). Option (a) runs the wrong way: releasing stored energy happens in respiration. Options (c) and (d), oxidising food to give CO₂ and water and taking in oxygen, both describe respiration.
Photosynthesis happens in chloroplasts: the light reactions split water and release oxygen, and the dark reactions (Calvin cycle) fix carbon. Notice how the two processes mirror each other and together keep the oxygen and carbon cycles in balance.
Answer as per the official UPSC answer key.
Which of the following statements is/are correct regarding vegetative propagation of plants?
- 1. Vegetative propagation produces clonal population.
- 2. Vegetative propagation helps in eliminating the virus.
- 3. Vegetative propagation can be practiced most of the year.
Select the correct answer using the code given below.
Answer (c) & explanation
Vegetative propagation, by cuttings, grafting, layering or tubers, gives genetically identical clones (1 correct) and can be done for most of the year (3 correct). Statement 2 is wrong: it passes on viruses present in the parent tissue rather than eliminating them. So the answer is (c).
To get virus-free plants, growers use meristem culture, since the growing tip of a plant is often free of virus. Banana, potato and sugarcane are often propagated this way. Notice how clonal crops are uniform but share the same weaknesses, so one disease can wipe out whole fields.
Answer as per the official UPSC answer key.
Consider the following techniques/phenomena :
- 1. Budding and grafting in fruit plants
- 2. Cytoplasmic male sterility
- 3. Gene silencing
Which of the above is/are used to create transgenic crops?
Answer (b) & explanation
Transgenic crops carry genes from another species. Cytoplasmic male sterility systems, such as GM mustard's barnase–barstar system, and gene silencing through RNAi, used in virus-resistant papaya and non-browning apples, are built in through genetic engineering. So 2 and 3 are correct (b). Budding and grafting are traditional propagation methods that join plant parts but change no genes, so options with 1 fail.
India has approved only Bt cotton for commercial cultivation, while DMH-11 mustard got environmental release approval in 2022. Notice how biotechnology meets policy, trade and farmer concerns.
Answer as per the official UPSC answer key.
Among the following organisms, which one does not belong to the class of other three?
Answer (a) & explanation
Mites, scorpions and spiders are arachnids: they have eight legs, two main body parts and no antennae. The crab is a crustacean, with ten legs and two pairs of antennae, so it is the odd one out (a). All four belong to the phylum Arthropoda, with jointed legs and an exoskeleton.
Other arthropod classes include insects (six legs, three body parts, one pair of antennae) and myriapods such as centipedes. Notice how counting legs and antennae is often enough to classify an animal, a handy shortcut for biology questions.
Answer as per the official UPSC answer key.
Consider the following pairs :
| Vitamin | Deficiency disease
| 1. Vitamin C | Scurvy
| 2. Vitamin D | Rickets
| 3. Vitamin E | Night blindness
Which of the pairs given above is/are correctly matched?
Answer (a) & explanation
Pairs 1 and 2 are correct (a). A lack of vitamin C causes scurvy, with bleeding gums, and a lack of vitamin D causes rickets, with soft bones in children. Pair 3 is wrong: night blindness is caused by a lack of vitamin A. Vitamin E deficiency mainly affects nerves and red blood cells.
Other links worth knowing: vitamin B1 and beriberi, B3 and pellagra, B12 and pernicious anaemia, and vitamin K and poor blood clotting. Notice how deficiency diseases tie biology to public policy, such as food fortification and the Vitamin A supplementation programme.
Answer as per the official UPSC answer key.
Mycorrhizal biotechnology has been used in rehabilitating degraded sites because mycorrhiza enables the plants to
- 1. resist drought and increase absorptive area
- 2. tolerate extremes of pH
- 3. resist disease infestation
Select the correct answer using the codes given below.
Answer (d) & explanation
All three are correct (d). Mycorrhiza is a partnership between a fungus and plant roots. The fungal threads extend the absorbing area of roots far into the soil, helping the plant take up water and resist drought (1). They help plants tolerate extremes of pH, salinity and heavy metals in poor soils (2). They also protect roots against soil pathogens by forming a barrier and competing with them (3). This is why mycorrhizal inoculants are used to rehabilitate degraded sites such as mine spoils. So (a), (b) and (c) leave out real benefits.
Notice the main benefit: mycorrhiza greatly improves phosphorus uptake. About 80% of land plants form such partnerships. TERI in India developed mycorrhizal biofertilisers for wasteland reclamation. Trap: all three effects are documented.
Answer as per the official UPSC answer key.
Recombinant DNA technology (Genetic Engineering) allows genes to be transferred
- 1. across different species of plants
- 2. from animals to plants
- 3. from microorganisms to higher organisms
Select the correct answer using the codes given below.
Answer (d) & explanation
All three are correct (d). Because the genetic code is universal, a gene from one organism can work in another. Recombinant DNA technology therefore allows transfer across plant species (1), from animals to plants, as in trials with a fish antifreeze gene in tomato (2), and from microbes to higher organisms, as with the Bt gene in cotton and the human insulin gene in bacteria in reverse (3). So options (a), (b) and (c) leave out real possibilities.
Notice the tools: restriction enzymes cut DNA, ligase joins it, and plasmids or Agrobacterium carry it. Newer CRISPR-Cas9 editing (Nobel 2020) changes a plant's own genes; India exempted such SDN-1 and SDN-2 edits from GM rules in 2022. Trap: the universality of the code makes all three transfers possible.
Answer as per the official UPSC answer key.
Improper handling and storage of cereal grains and oilseeds result in the production of toxins known as aflatoxins which are not generally destroyed by normal cooking process. Aflatoxins are produced by
Answer (c) & explanation
Moulds is correct (c). Aflatoxins are produced by the moulds (fungi) Aspergillus flavus and A. parasiticus, which grow on damp or poorly stored groundnuts, maize, cottonseed, spices and other grains. They are potent liver toxins and among the strongest natural carcinogens, and normal cooking does not destroy them. (a) is wrong: bacteria cause other food poisoning, such as botulinum toxin. (b) and (d) are wrong: protozoa and viruses do not make aflatoxins.
Notice the safety rules: FSSAI sets limits on aflatoxin in food, and aflatoxin M1 appears in milk when cattle eat contaminated feed. Good drying to low moisture and proper storage prevent it. Aflatoxin rejections have hit Indian groundnut and spice exports to the EU. Trap: toxins in food are often blamed on bacteria.
Answer as per the official UPSC answer key.
Consider the following organisms :
- 1. Agaricus
- 2. Nostoc
- 3. Spirogyra
Which of the above is/are used as biofertilizer/biofertilizers?
Answer (b) & explanation
Nostoc only is correct (b). Nostoc is a blue-green alga (cyanobacterium) that fixes atmospheric nitrogen in special cells called heterocysts, so it is used as a biofertiliser in paddy fields, along with Anabaena (2). Item 1 is wrong: Agaricus is an edible mushroom, a fungus that does not fix nitrogen. Item 3 is wrong: Spirogyra is a green alga that does not fix nitrogen. So (a), (c) and (d) fail.
Notice the other biofertilisers: Rhizobium in legume root nodules, free-living Azotobacter and Azospirillum, the Azolla–Anabaena partnership in rice fields, and mycorrhizal fungi that help absorb phosphorus. Biofertilisers are promoted under the National Mission on Natural Farming. Trap: all three are 'lower' organisms, but only one fixes nitrogen.
Answer as per the official UPSC answer key.
Which of the following diseases can be transmitted from one person to another through tattooing?
- 1. Chikungunya
- 2. Hepatitis B
- 3. HIV-AIDS
Select the correct answer using the codes given below.
Answer (b) & explanation
Hepatitis B and HIV are correct (b). Tattoo needles shared or reused without sterilising can carry blood-borne viruses: Hepatitis B (2), Hepatitis C, and HIV (3). Item 1 is wrong: chikungunya spreads through the bite of infected Aedes mosquitoes (aegypti and albopictus), not through blood contact in tattooing. So (a), (c) and (d) fail.
Notice the prevention: single-use needles, sterilised equipment and fresh ink pots. India's blood banks screen donors for HBV, HCV and HIV and often defer people with recent tattoos for 6–12 months. Hepatitis B has a vaccine in India's Universal Immunisation Programme; HIV and Hepatitis C do not. Trap: chikungunya is a viral disease, but its route is the mosquito.
Answer as per the official UPSC answer key.
Consider the following minerals :
- 1. Calcium
- 2. Iron
- 3. Sodium
Which of the minerals given above is/are required by human body for the contraction of muscles?
Answer (d) & explanation
All three per UPSC's key (d), but iron's place is doubtful. Sodium ions rush into nerve and muscle cells to create the action potential that triggers contraction (3). Calcium released inside the muscle cell binds troponin and lets actin and myosin slide (1). Iron is not directly part of the contraction mechanism; it sits in myoglobin and haemoglobin, supplying the oxygen muscles need to keep working, so many argue for (c). UPSC counted iron as required. (a) and (b) fail on any reading.
Notice the others: potassium restores the resting state, and magnesium helps muscles relax; low calcium causes tetany and cramps. Anaemia from iron deficiency, common in India, causes muscle fatigue. Trap: 'required for contraction' can be read narrowly or broadly.
Answer as per the official UPSC answer key.
Fruits stored in a cold chamber exhibit longer storage life because
Answer (c) & explanation
The rate of respiration is decreased is correct (c). Harvested fruit is still alive and keeps respiring, burning its stored sugars, losing water and ripening further. Low temperature slows respiration and enzyme action, and also slows the growth of microbes that cause rot, so the fruit lasts longer. (a) is wrong: cold chambers are dark, but blocking sunlight is not the main reason. (b) is wrong: higher CO₂ helps only in special controlled-atmosphere storage, not in a simple cold chamber. (d) is wrong: humidity is kept moderate to prevent shrivelling, but it is not the main reason.
Notice the related methods: ethylene scrubbing slows ripening, and irradiation extends shelf life of onions and potatoes. India loses a large share of fruits and vegetables after harvest; the Integrated Cold Chain scheme under PM Kisan SAMPADA tackles this. Trap: cold slows life processes; that is the core idea.
Answer as per the official UPSC answer key.
Many transplanted seedlings do not grow because
Answer (c) & explanation
Most of the root hairs are lost is correct (c). Root hairs, thin outgrowths near the root tips, absorb most of a plant's water and minerals. They are delicate and are torn off when a seedling is uprooted, so the transplanted plant cannot take up enough water and wilts, sometimes dying. (a) is wrong: the new soil usually has adequate minerals. (b) is wrong: root hairs do not 'grip too hard'. (d) is wrong: leaf damage can happen but is not the main reason.
Notice the practice: gardeners transplant with a ball of soil around the roots, water well, shade the seedlings, and transplant in the evening to cut transpiration. Paddy is transplanted from nurseries, while Direct Seeded Rice avoids transplanting altogether and saves water. Trap: the problem is at the roots, not the soil.
Answer as per the official UPSC answer key.
Which of the following statements is/are correct?
- 1. Viruses lack enzymes necessary for the generation of energy.
- 2. Viruses can be cultured in any synthetic medium.
- 3. Viruses are transmitted from one organism to another by biological vectors only.
Select the correct answer using the codes given below.
Answer (a) & explanation
Statement 1 only is correct (a). Viruses have no energy-making enzymes or metabolism of their own; they use the host cell's machinery to make copies (1). Statement 2 is wrong: viruses grow only in living cells, such as cell cultures or embryonated eggs, not in a synthetic, cell-free medium. Statement 3 is wrong: viruses spread by many routes: air (influenza, COVID-19), water and food (hepatitis A), contact, blood (HIV) and also vectors (dengue). So (b), (c) and (d) fail.
Notice the debate: viruses are at the edge of life, active only inside cells. Bacteriophages infect bacteria and are studied as alternatives to antibiotics. India's NIV, Pune is the main virology institute. Trap: 'only' makes statement 3 too narrow.
Answer as per the official UPSC answer key.
Which of the following leaf modifications occurs/occur in desert areas to inhibit water loss?
- 1. Hard and waxy leaves
- 2. Tiny leaves or no leaves
- 3. Thorns instead of leaves
Select the correct answer using the codes given below.
Answer (d) & explanation
All three are correct (d). Desert plants (xerophytes) cut transpiration in every way. Hard, waxy leaves with a thick cuticle reduce evaporation (1). Tiny leaves or no leaves reduce the surface losing water (2). Thorns or spines instead of leaves, as in cactus, reduce water loss further, while the green stem does photosynthesis (3). So options (a), (b) and (c) leave out real adaptations.
Notice the other adaptations: sunken stomata, stomata that open at night (CAM photosynthesis in cacti and pineapple), deep tap roots, and fleshy succulent stems that store water. India's Thar has khejri, which has deep roots, and ker with tiny leaves. Trap: all three are textbook xerophyte features.
Answer as per the official UPSC answer key.
What are the reasons for the people’s resistance to the introduction of Bt brinjal in India?
- 1. Bt brinjal has been created by inserting a gene from a soil fungus into its genome.
- 2. The seeds of Bt brinjal are terminator seeds and therefore, the farmers have to buy the seeds before every season from the seed companies.
- 3. There is an apprehension that the consumption of Bt brinjal may have adverse impact on health.
- 4. There is some concern that the introduction of Bt brinjal may have adverse effect on the biodiversity.
Select the correct answer using the codes given below :
Answer (c) & explanation
Statements 3 and 4 are correct (c). The 2010 moratorium on Bt brinjal followed public fears about possible health effects of eating it (3), and concern that it could contaminate India's many native brinjal varieties, since India is a centre of origin of brinjal (4). Statement 1 is wrong: the Bt gene comes from a bacterium, Bacillus thuringiensis, not a fungus. Statement 2 is wrong: Bt brinjal seeds are not terminator seeds; terminator technology was never commercialised, and public-sector Bt brinjal varieties could be saved. So (a), (b) and (d) fail.
Notice the context: GEAC cleared it in 2009, but Jairam Ramesh imposed the moratorium after public hearings in February 2010. Bangladesh has grown Bt brinjal since 2014. Trap: two plausible myths are mixed with two real concerns.
Answer as per the official UPSC answer key.
Other than resistance to pests, what are the prospects for which genetically engineered plants have been created?
- 1. To enable them to withstand drought
- 2. To increase the nutritive value of the produce
- 3. To enable them to grow and do photosynthesis in spaceships and space stations
- 4. To increase their shelf life
Select the correct answer using the codes given below :
Answer (c) & explanation
Items 1, 2 and 4 are correct (c). Genetic engineering has produced crops for drought tolerance, such as Argentina's HB4 wheat and drought-tolerant maize (1), better nutrition, such as Golden Rice with beta-carotene, approved in the Philippines (2), and longer shelf life, such as the Flavr Savr tomato (1994) and non-browning Arctic apples (4). Item 3 is wrong: there are no GM plants created to photosynthesise in spaceships; plants are grown in space experiments, but not engineered for that purpose. So (a), (b) and (d) fail.
Notice India's position: Bt cotton remains the only GM crop grown commercially; GM mustard DMH-11 got environmental release approval in 2022 but is in court, and genome-edited rice varieties released in May 2025 are not classed as GM. Trap: space farming exists, but not as a GM aim.
Answer as per the official UPSC answer key.
Consider the following kinds of organisms :
- 1. Bacteria
- 2. Fungi
- 3. Flowering plants
Some species of which of the above kinds of organisms are employed as biopesticides?
Answer (d) & explanation
All three are correct (d). Biopesticides come from living organisms of all three kinds. Bacteria: Bacillus thuringiensis (Bt) makes proteins toxic to caterpillars (1). Fungi: Trichoderma controls soil-borne diseases, and Beauveria and Metarhizium infect insects (2). Flowering plants: neem (azadirachtin) and pyrethrum from chrysanthemum flowers act as natural insecticides (3). So options (a), (b) and (c) leave out real sources.
Notice the advantages: biopesticides are specific, biodegradable and safer for pollinators. Viruses such as NPV (nuclear polyhedrosis virus) are also used. In India they are registered under the Insecticides Act, 1968, and promoted under the National Mission on Natural Farming. Trap: plants are often forgotten as a source.
Answer as per the official UPSC answer key.
With reference to ‘stem cells’, frequently in the news, which of the following statements is/are correct?
- 1. Stem cells can be derived from mammals only.
- 2. Stem cells can be used for screening new drugs.
- 3. Stem cells can be used for medical therapies.
Select the correct answer using the codes given below :
Answer (b) & explanation
Statements 2 and 3 are correct (b). Stem cells are unspecialised cells that can divide and turn into other cell types. They are used to grow tissues in the lab to screen new drugs for safety and effect (2), and in therapies such as bone-marrow transplants for leukaemia (3). Statement 1 is wrong: stem cells exist in all multicellular organisms, including plants (meristems), not only mammals. So (a), (c) and (d) fail.
Notice the types: embryonic (pluripotent), adult (multipotent) and induced pluripotent stem cells (iPSCs), for which Shinya Yamanaka shared the 2012 Nobel Prize. India's ICMR guidelines (2017) permit only approved stem-cell therapies, mainly bone-marrow transplants. Trap: 'mammals only' is too narrow.
Answer as per the official UPSC answer key.