After analysing the Question Paper, it can be concluded that the examiner has tested the knowledge of the basics, understanding of applications of science in real life and the current issues related to the scientific field.
There were 10 Questions from Science & Technology in 2023, of which
- 1 Question from Genetics (Aerial Metagenomics)
- 2 Questions from Biotechnology (Microsatellite DNA, Biofilters)
- 1 Question from Physics (Accelerometer)
- 1 Questions from Energy (Uranium)
- 1 Questions from Defence (Missiles)
- 1 Question from Diseases (Wolbachia)
- 1 Question from Chemistry (Carbon Fibres)
- 2 Questions from Space (Stars, Navigation)
The level of the questions was moderate.
Most of the questions were aimed at testing the analytical abilities of the candidates.
Solved PYQs Science & Technology With Explanation 2023 UPSC Prelims (Previous Year Questions)
1. ‘Wolbachia method’ is sometimes talked about with reference to which one of the following?
(a) Controlling the viral diseases spread by mosquitoes
(b) Converting crop residues into packing material
(c) Producing biodegradable plastics
(d) Producing biochar from thermo-chemical conversion of biomass
Answer- a
Explanation:
How mosquitoes spread diseases ?
- Mosquitoes do not naturally carry viruses – they can only get them from infected people.
- Since only female mosquitoes bite humans, only female mosquitoes can transmit viruses.
- Mosquitoes pick up viruses by biting infected people. When they bite again, they can transmit the virus to the next person. This is how mosquito-borne diseases spread.
- The Aedes aegypti mosquito is the main transmitter of dengue, Zika, chikungunya and yellow fever viruses.
- Aedes aegypti mosquitoes originated in Africa, but they have spread through tropical and subtropical regions around the world.
About Wolbachia
- Wolbachia is one of the world’s most common types of bacteria, present in 50% of all insect species, including bees, beetles, butterflies, moths, and fruit flies. Wolbachia bacteria cannot make people or animals (for example, fish, birds, pets) sick.
- Wolbachia lives inside insect cells and is passed from one generation to the next through an insect’s eggs. Aedes aegypti mosquitoes don’t normally carry Wolbachia, however many other mosquitoes do.
- Wolbachia blocks viruses like dengue, chikungunya and Zika from growing in the bodies of Aedes aegypti mosquitoes. This means that Wolbachia mosquitoes have a reduced ability to transmit viruses to people.
- When Wolbachia is established in a mosquito population it results in a decreasing incidence of dengue, Zika, chikungunya.
- World Mosquito Program, breeds Wolbachia mosquitoes. Then, in partnership with local communities, release them into areas affected by mosquito-borne diseases.
- Which means less risk of disease in communities where Wolbachia is established in the local mosquito population.
- Wolbachia method can protect communities from mosquito-borne diseases without posing risk to natural ecosystems. This method is natural and self-sustaining.
- People are constantly exposed to Wolbachia through the foods they eat and the insects that bite them, but it causes no known health risks. It also does not affect the food chains of other species because Wolbachia does not reduce mosquito populations.
- Other methods of controlling mosquitoes are Insecticide spraying, the Sterile Insect Technique, the Incompatible Insect technique, and Genetic Modification. But these techniques are not self-sustaining.
2. ‘Aerial metagenomics’ best refers to which one of the following situations?
(a) Collecting DNA samples from air in a habitat at one go
(b) Understanding the genetic makeup of avian species of a habitat
(c) Using air-borne devices to collect blood samples from moving animals
(d) Sending drones to inaccessible areas to collect plant and animal samples from land surfaces and water bodies
Answer- a
Explanation:
Metagenomics:
Meta derives from the Greekword, which encompasses a wide array of meanings, such as “with”, “after”, “alongside”, “on top of” and “beyond”.
Metagenomics, is the study of the total genetic material directly obtained from the microorganisms living in a particular environment, like microbes living in the animal gut or in any particular ecological environment. Metagenomics projects are used to study the genomics of community of organisms.
Applications of Metagenomics
- It helps to study the diversity of microbial communities and how the diversity of these microbes changes with changes in the environment.
- Metagenomics may also help in identifying novel genes or enzymes with the significant industrial applications. For example, the study of microbial communities living in extreme environments, like high temperature sulphur springs can help to identify the novel enzymes that are resistant and functional at such high temperatures. Thus, metagenomics has applications in understanding the genomes of gut microbes, throat microbes, microbes present on a toilet seat, and many more.
- It provides an insight about the genome of diverse forms of microbes and their correlations. For example, study of genomes of diverse forms of viruses may provide an understanding about virus-host interaction, epidemiology and also evolution of viruses.
Environmental DNA (eDNA) and Aerial Metagenomics
DNA can be easily released by an organism, all living beings constantly shed bits of DNA, left behind from skin, scales, hair, urine, feces, pollen and more into environment, such a DNA is called Environmental DNA (eDNA). This DNA can be found in air, water, or soil.
All species shed DNA during life or in death, providing an opportunity to monitor biodiversity via environmental DNA (eDNA).
This environmental DNA, or eDNA, has “changed everything” about how scientists study biodiversity and conservation.
Aerial Metagenomics is about extracting eDNA from the atmosphere. It involves plucking the DNA concerned from thin air.
3. ‘Microsatellite DNA’ is used in the case of which one of the following?
(a) Studying the evolutionary relationships among various species of fauna
(b) Stimulating ‘stem cells’ to transform into diverse functional tissues
(c) Promoting clonal propagation of horticultural plants
(d) Assessing the efficacy of drugs by conducting series of drug trials in a population
Answer- a
Explanation:
Microsatellites, also known as Short Tandem Repeats, are short segments of DNA, typically one to six base pairs long, that repeat multiple times at specific genomic locations. These non-coding sequences vary among individuals, making them useful as polymorphic markers for studying inheritance, creating DNA fingerprints, and analyzing genetic diversity. Their unique patterns can be inherited and are valuable for evolutionary studies, pedigree analysis, and understanding population structure.
4. Consider the following actions:
- Detection of car crash/collision which results in the deployment of airbags almost instantaneously.
- Detection of accidental free fall of a laptop towards the ground which results in the immediate turning off of the hard drive
- Detection of the tilt of smartphone which results in the rotation of display between portrait and landscape mode
In how many of the above actions is the function of the accelerometer required?
(a) Only one
(b) Only two
(c) All three
(d) None
Answer- c
Explanation:
An accelerometer is a device that measures acceleration forces, such as gravity and motion, by converting them into electrical signals.
An accelerometer works by utilizing an electromechanical sensor that is designed to measure either static or dynamic acceleration.
Static acceleration is the constant force acting on a body, like gravity or friction. These forces are predictable and uniform to a large extent. For example, the acceleration due to gravity is constant at 9.8 m/s – and the gravitation force is almost the same at every point on Earth.
Dynamic acceleration forces are non-uniform, and the best example is vibration or shock. A car crash is an excellent example of dynamic acceleration
when an accelerometer detects a sudden change in a car’s speed, signaling an imminent collision, it triggers an electrical circuit that makes the airbags inflate.
Hence Statement 1 is correct.
In a laptop, the accelerometer senses freefall and parks the hard drive—usually—before the device hits the ground.
Hence Statement 2 is correct.
Accelerometer in cellphone, MP3 player, or handheld games console, sense when you tilt it from side to side. That’s how a cellphone automatically figures out when to switch the screen layout from portrait to landscape.
Hence Statement 3 is correct.
Accelerometer in Rockets measure changes in rocket speed ,apogee (when a craft is at its maximum distance from Earth or another mass, so its acceleration due to gravity is at a minimum) and orientation (because tilting something changes the way gravity acts on it and the force it feels).
Accelerometers are also widely used in inertial navigation and guidance systems in such things as airplane and ship autopilots.
Applications of Accelerometer
Accelerometers are versatile sensors used in various sectors to measure acceleration and orientation. Key applications include:
- Consumer Electronics: Integrated into smartphones and wearables for screen orientation, step tracking, and gaming.
- Automotive: Essential for vehicle dynamics, airbag deployment, and anti-theft systems.
- Aerospace and Aviation: Used in navigation systems and aircraft performance monitoring.
- Industrial: Employed for vibration analysis, enabling predictive maintenance.
- Healthcare: Assist in patient monitoring and rehabilitation by tracking body movement.
- Building Monitoring: Detect vibrations in structures to assess stability and seismic activity.
5. Consider the following statements:
- Ballistic missiles are jet-propelled at subsonic speeds throughout their flights, while cruise missiles are rocket-powered only in the initial phase of flight.
- Agni-V is a medium-range supersonic cruise missile, while BrahMos is a solid-fuelled intercontinental ballistic missile.
Which of the statements given above is/are correct?
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
Answer- d
Explanation:
Ballistic missiles
Ballistic missiles are powered initially by a rocket or series of rockets in stages, but then follow an unpowered trajectory that arches upwards before descending to reach its intended target. Ballistic missiles can carry either nuclear or conventional warhead.
There are four general classifications of ballistic missiles based on their range, or the maximum distance the missile can travel:
- Short-range: less than 1,000 kilometers (approximately 620 miles), also known as “tactical” ballistic missiles.
- Medium-range: between 1,000 and 3,000 kilometers (approximately 620-1,860 miles), also known as “theater” ballistic missiles.
- Intermediate-range: between 3,000 and 5,500 kilometers (approximately 1,860-3,410 miles)
- Long-range: more than 5,500 kilometers (approximately 3,410 miles), also known as intercontinental or strategic ballistic missiles.
- Intercontinental ballistic missiles (ICBMs) can fly much further than the minimum range; for example, Russia could hit Chicago with an ICBM launched from the Krasnoyarsk ICBM base, which is located 9,156 kilometers (5,689miles) away.
Cruise missiles
Cruise missiles are unmanned vehicles that are propelled by jet engines, much like an airplane. They can be launched from ground, air, or sea platforms.
Cruise missiles remain within the atmosphere for the duration of their flight and can fly as low as a few meters off the ground.
Flying low to the surface of the earth expends more fuel but makes a cruise missile very difficult to detect.
Cruise missiles are self-guided and use multiple methods to accurately deliver their payload, including terrain mapping, global positioning systems (GPS) and inertial guidance, which uses motion sensors and gyroscopes to keep the missile on a pre-programmed flight path.
As advanced cruise missiles approach their target, remote operators can use a camera in the nose of the missile to see what the missile sees. This gives them the option to manually guide the missile to its target or to abort the strike.
Brahmos Cruise missile
- Brahmos is a two-stage missile with a solid propellant booster engine as its first stage which brings it to supersonic speed and then gets separated. The liquid ramjet or the second stage then takes the missile closer to 3 Mach speed in cruise phase. Stealth technology and guidance system with advanced embedded software provides the missile with special features.
- The missile has flight range of upto 290 km with supersonic speed , it operates on Fire and Forget principle
- The range of the missile was originally capped at 290km as per obligations of the Missile Technology Control Regime. Following India’s entry into the club in June 2016, the range has been extended to 450km and work is on to extend it to 600km and beyond
Agni-V Ballistic missile
- Agni-V uses a three-stage solid fuelled engine and is capable of striking targets at ranges upto 5,000 Kms and can reach most parts of China.
- The Agni-V, which currently has range of up to 5,000 kilometre as officially claimed technically qualifies only as an intermediate range ballistic missile (IRBM), and not an Intercontinental ballistic missiles (ICBM) because ICBMs are missiles with ranges over 5,500 km. But the official claim of 5,000 km probably understates the range of the missile, with many reports claiming it is a true ICBM with an 8,000 km range.
- On March 11,2024 , the Indian Defense Research and Development Organization (DRDO) undertook the maiden test of its indigenously developed Agni-V MIRV (Multiple Independently Targetable Re-Entry Vehicle) missile. The flight test, named Mission Divyastra .
- With MIRV technology a single intercontinental ballistic missile (ICBM) can carry and deliver multiple warheads at different locations several hundred kilometers apart.
- MIRV capability is a complex technology and India is among a small group of countries – the United States, United Kingdom, Russia, France, and China – that have developed it.
Hence both the statements are incorrect.
6. Consider the following statements:
Statement- I: India despite having uranium deposits, depends on coal for most of its electricity production.
Statement- II: Uranium, enriched to the extent of at least 60%, is required for the production of electricity.
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
Answer- c
Explanation:
India’s three-stage nuclear power programme is a long-term plan that involves the use of three different types of reactors to produce energy.
The first stage involves uranium-fueled heavy water reactors (HWRs) that produce plutonium.
The second stage, comprising of Fast Breeder Reactors (FBRs) are fuelled by mixed oxide of Uranium238 and Plutonium239, recovered by reprocessing of the first stage spent fuel
The third and final stage involves using the recovered materials to create 232Th/233U fuel for advanced heavy water reactors (HWRs)
This programme is necessary because India has abundant thorium reserves but little uranium, and the use of a thorium fuel cycle in the third stage is a key feature of the programme.
Indian Prime Minister Narendra Modi in March 2024 witnessed the start of fuel loading at the 500 MWe Prototype Fast Breeder Reactor at Kalpakkam in Tamil Nadu in Fast breeder reactors form the second stage of India’s three-stage nuclear programme. India is presently in second stage of India’s three-stage nuclear programme
Since thorium is used in the third stage, presently, India depends substantially on Coal for Power generation
Hence Statement I is correct
Uranium is a naturally occurring radioactive element
There are three natural isotopes of uranium — uranium-234 (U-234), uranium-235 (U-235) and uranium-238 (U-238). U-238 is the most common one, accounting for around 99 per cent of natural uranium found on earth. Most nuclear reactors use fuels containing U-235, however, natural uranium typically contains only 0.72 per cent of U-235 and, most reactors need a higher concentration of this isotope in their fuel. Therefore, the U-235 concentration is being artificially increased through a process called enrichment.
Uranium enrichment is the process, through which the isotopic proportion of U-235 is increased from 0.72 per cent to up to 94 per cent.
Uranium is considered low-enriched if its isotopic proportion of U-235 remains below 20 per cent. Most commercial reactors use low-enriched uranium (LEU) below five per cent as fuel, which is also often referred to as “reactor-grade uranium”. LEU does not deteriorate and can be safely stored for many years.
If uranium is enriched beyond 20 per cent, it is considered highly enriched. Uranium with such high isotopic proportions of U-235 is mostly used in naval propulsion reactors (for example in submarines), nuclear weapons and some research reactors.
Hence Statement II is incorrect.
7. Consider the following:
1. Carbon fibres are used in the manufacture of components used in automobiles and aircrafts.
2. Carbon fibres once used cannot be recycled.
Which of the statements given above is fare correct?
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
Answer- a
Explanation:
The Carbon fibres are composed of carbonised polymers, which are lengthy chains of molecules joined by strong bonds between carbon atoms. A precursor material is heated to around 3,000°C in an environment of inert gases to create the fibres. The most commonly used precursor is polyacrylonitrile (PAN), which is produced by the petrochemicals industry. Alternatively, pitch made from coal tar is occasionally utilised. The fibres are spun into yarns, molded into tapes, or threaded into bobbins once they have carbonised. They can also be woven into fabric sheets, depending on the intended use.
Because it is incredibly strong and lightweight, carbon fibre is appealing. Being the strongest fibre, they have 10 times the strength of steel and eight times the strength of aluminum. The carbon fibre is also five times lighter than steel and half the weight, or less, of aluminum. Nor does it corrode. Therefore, they are used in aircrafts and automobiles.
Hence Statement 1 is correct.
On their own, carbon fibres are brittle and can break easily. But their strength comes in tension (they resist being pulled apart). So, the fibres need to be aligned in such a way to impart their strength by distributing loads throughout a structure.
Carbon fibres can be made from manufacturing offcuts or recycled material and can themselves be recycled.
Hence Statement 2 is incorrect.
8. With reference to the role of biofilters in Recirculating Aquaculture System, consider the following statements:
1. Biofilters provide waste treatment by removing uneaten fish feed.
2. Biofilters convert ammonia present in fish waste to nitrate.
3. Biofilters increase phosphorus as a nutrient for fish in water.
How many of the statements given above are correct?
(a) Only one
(b) Only two
(c) All three
(d) None.
Answer- b
Explanation-
About Recirculatory Aquaculture System (RAS )
- Instead of the traditional method of growing fish outdoors in open ponds and raceways, in RAS system fish are typically reared in indoor/outdoor tanks in a controlled environment.
- In RAS water is recycled and reused by passing it through mechanical and biological filters and after suspended matter is removed.
- The steps in RAS include solids removal, ammonia removal, CO2 removal and oxygenation.
Biolfilters: A biological filter consists of various material such as plastic beads (bioball), net fiber, molluscan shells, fiberglass, ceramic or rock that has large amounts of surface area for colonizing the nitrifying bacteria cells which grow on all surfaces of the biofilter media.
How does filtration works?
To remove these wastes, the mechanical filters and biofilter or biological filters are used.
Mechanical filtration: Mechanical filtration of the outlet water from the fish tanks is used for the removal of suspended organic and inorganic wastes. The removal of solid waste including uneaten fish feed is the first stage in serial filtration design. Smaller particles of organic sediments are consumed by microscopic organisms including bacteria. But not all the organic matter is removed in the mechanical filter; the finest particles will pass through the filter along with dissolved compounds such as phosphate and nitrogen which are then removed using biofilters.
Hence Statement 1 is correct.
Biolfilteration: The breakdown of organic matter and ammonia is a biological process carried out by bacteria in the bio-filter. Heterotrophic bacteria oxidize/breakdown the left organic matter by consuming oxygen and producing carbon dioxide and ammonia. Nitrifying bacteria convert ammonia into nitrite and finally into nitrate. The bacteria that convert ammonia to nitrite are known collectively by their genus name Nitrosomonas. Like ammonia, the nitrite produced by the Nitrosomonas bacteria is toxic to aquatic organisms and must be oxidized further to a less toxic form of nitrogen. This is accomplished by genus of bacteria called Nitrobacter.
Hence Statement 2 is correct.
Efficiency of bio-filtration depends primarily on Water temperature, oxygen and pH level. To reach an acceptable nitrification rate, water temperatures should be kept within 10 to 35 °C (optimum around 30 °C) and pH levels between 7 and 8. A lower pH level reduces the efficiency of the bio-filter. Under anaerobic conditions, hydrogen sulfide (H2S) can be produced, especially in saltwater systems. This gas is extremely toxic to fish, even in low concentrations, and fish will be killed if hydrogen sulfide is generated in the system.
Note: Phosphate is an inert substance, with no toxic effect, but nitrogen in the form of free ammonia (NH3) is toxic and needs to be transformed into non-toxic form in the bio-filter.
How Phosphates are removed from RAS?
In recirculating aquaculture systems, cultivated fish cannot incorporate all the phosphate contained in the feed. Excess phosphate ends up in the culture water and in the sludge produced, which can harm other aquatic life in the area by causing algae blooms. One method of phosphorus removal is adsorption (adsorbent RhizoSorb (base material of aluminum oxide) is used) which is a surface phenomenon that is often used to bind dissolved pollutants to a solid-phase medium and remove them from water. Thus biofliters reduce the amount of phosphorus in water.
Hence Statement 3 is incorrect.
9. Consider the following pairs:
Objects in space Description
1. Cepheids Giant clouds of dust and gas in space
2. Nebulae Stars which brighten and dim periodically
3. Pulsars out Neutron stars that are formed when massive stars run of fuel and collapse
How many of the above pairs are correctly matched?
(a) Only one
(b) Only two
(c) All three
(d) None
Answer- a
Explanation:
Cepheids, also called Cepheid Variables, are stars which brigthen and dim periodically. This behavior allows them to be used as cosmic yardsticks out to distances of a few tens of millions of light-years
A nebula is a giant cloud of dust and gas in space. Some nebulae (more than one nebula) come from the gas and dust thrown out by the explosion of a dying star, such as a supernova. Other nebulae are regions where new stars are beginning to form.
Hence 1 and 2 are incorrectly matched.
Pulsars are rapidly rotating neutron stars that blast out pulses of radiation at regular intervals ranging from seconds to milliseconds.
A pulsar is the crushed core of a massive star that ran out of fuel, collapsed under its own weight and exploded as a supernova
Hence 3 is correctly matched.
10. Which one of the following countries has its own Satellite navigation system?
(a) Australia
(b) Canada
(c) Israel
(d) Japan
Answer- d
Explanation:
Global navigation satellite system (GNSS) is a general term describing any satellite constellation that provides positioning, navigation, and timing (PNT) services on a global or regional basis.
GPS
The Global Positioning System (GPS) is a U.S.-owned utility that provides users with positioning, navigation, and timing (PNT) services.
GPS is the most prevalent GNSS, other nations are fielding, or have fielded, their own systems to provide complementary, independent PNT capability.
The GPS space segment consists of a constellation of satellites transmitting radio signals to users.
The United States is committed to maintaining the availability of at least 24 operational GPS satellites, 95% of the time.
GPS satellites fly in medium Earth orbit (MEO) at an altitude of approximately 20,200 km (12,550 miles). Each satellite circles the Earth twice a day.
Other Global Navigation Satellite Systems (GNSS)
BeiDou Navigation Satellite System (BDS)
BeiDou, or BDS, is a global GNSS owned and operated by the People’s Republic of China. BDS was formally commissioned in 2020. The operational system consists of 35 satellites. BDS was previously called Compass.
Galileo
Galileo is a global GNSS owned and operated by the European Union. The EU declared the start of Galileo Initial Services in 2016 and plans to complete the system of 24+ satellites in 2021.
GLONASS
GLONASS (Globalnaya Navigazionnaya Sputnikovaya Sistema, or Global Navigation Satellite System) is a global GNSS owned and operated by the Russian Federation. The fully operational system consists of 24+ satellites.
Indian Regional Navigation Satellite System (IRNSS) / Navigation Indian Constellation (NavIC)
IRNSS is a regional GNSS owned and operated by the Government of India. IRNSS is an autonomous system designed to cover the Indian region and 1500 km around the Indian mainland. The system consists of 7 satellites. In 2016, India renamed IRNSS as the Navigation Indian Constellation (NavIC, meaning “sailor” or “navigator”).
Quasi-Zenith Satellite System (QZSS)
QZSS is a regional GNSS owned by the Government of Japan and operated by QZS System Service Inc. (QSS). QZSS complements GPS to improve coverage in East Asia and Oceania. Japan declared the official start of QZSS services in 2018 with 4 operational satellites, and plans to expand the constellation to 7 satellites by 2023 for autonomous capability.