Q.1) Consider the following statements: (UPSC 2023)
How many of the above statements are correct?
(a) Only one
(b) Only two
(c) All three
(d) None
Answer- c
Explanation:
Statement 1 is correct: Thermophiles are extremophiles that thrive at high temperatures, typically between 41 and 122 °C. Most thermophiles prefer temperatures between 60 and 80 °C. Pyrolobus fumarii, for instance, has been discovered at temperatures as high as 113° C, surpassing the boiling point of water.
Statement 2 is correct: Psychrophiles are organisms capable of growing and reproducing in cold temperatures, often exhibiting xerophilic and halophilic traits. Some microbes can continue growing below the freezing point of water, with reported minimum growth temperatures ranging from 0°C to as low as -70°C in practical cases.
Statement 3 is correct: Acidophiles are microorganisms that thrive in highly acidic environments. There are two types: extreme acidophiles, which flourish in environments with a pH below 3, and moderate acidophiles, which grow optimally in conditions with pH values ranging from 3 to 5.
Q.2) Consider the following statements in respect of probiotics: (UPSC 2022)
Which of the statements given above is/are correct?
(a) 1 only
(b) 2 only
(c) 1 and 3
(d) 2 and 3
Answer- c
Explanation:
Statement 1 is correct: Probiotics consist of live beneficial bacteria and/or yeasts.
Statement 2 is incorrect: Probiotics naturally inhabit various parts of the human body, not just the gut. While L. acidophilus is a probiotic bacterium found in the human gut, probiotics can also reside in the mouth, urinary tract, skin, lungs, and other locations.
Statement 3 is correct: Yogurt is a well-known food source of probiotics. Specific bacteria strains in yogurt, such as those containing ß-D-galactosidase, aid in breaking down lactose in dairy products into the sugars glucose and galactose. This enzymatic activity contributes to the digestion of milk sugars.
Q.3) Which of the following statements about carboxylic acids is/are correct? (NDA 2023)
Select the correct answer using the code given below.
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer- a
Explanation:
Statement 1 is correct: Simple aliphatic carboxylic acids are generally soluble in water. This solubility is due to the ability of the carboxylic acid functional group to form hydrogen bonds with water molecules. Carboxylic acids up to a certain chain length exhibit this characteristic.
Statement 2 is correct: Higher carboxylic acids may still exhibit solubility in water, although it generally decreases with an increase in the length of the hydrocarbon chain. Small carboxylic acids, such as formic acid and acetic acid, are more soluble than larger ones.
Statement 3 is incorrect: The acidity of a carboxylic acid is not solely determined by the number of carbon atoms in the hydrocarbon chain. The primary factor influencing the acidity of a carboxylic acid is the strength of the carboxylic acid functional group. The carboxyl group (-COOH) is what imparts acidity to carboxylic acids. It consists of a carbonyl group (C=O) and a hydroxyl group (-OH) attached to the same carbon atom. The hydrogen in the hydroxyl group can ionize in an aqueous solution, leading to the release of a proton (H+) and the formation of a carboxylate anion (COO⁻).
Q.4) Among the following crops, which one is the most important anthropogenic source of both methane and nitrous oxide? (UPSC 2022)
(a) Cotton
(b) Rice
(c) Sugarcane
(d) Wheat
Answer- b
Explanation:
Methane and nitrous oxide are significant contributors to global warming as greenhouse gases. Important anthropogenic sources of biogenic methane include wet rice fields, cattle, animal waste, landfills, and biomass burning.
Flooded rice cultivation has been identified as a prominent global agricultural source of anthropogenic methane (CH4) emissions. It has been estimated that global rice production accounts for approximately 11% of total anthropogenic CH4 emissions.
Paddy fields are also identified as potential sources of anthropogenic nitrous oxide (N2O) emissions. In paddies, both the soil and the rice plants release N2O into the atmosphere. The rice plant in the paddy serves as a conduit between the soil and the atmosphere for N2O emissions. Hence option b is correct.
Q.5) Consider the following: (UPSC 2021)
Which of the above can be cultured in artificial/synthetic medium?
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer- a
Explanation:
Statement 1 is correct: Bacteria can indeed be grown in synthetic culture media. Researchers have achieved significant advancements in synthetic biology, including rewriting the DNA of bacteria like Escherichia coli to create synthetic genomes with increased complexity.
Statement 2 is correct: Fungi, including allergologically important ones like Aspergillus fumigatus, Alternaria, Penicillium notatum, and Cladosporium herbarum, can be cultured in pure synthetic media. Synthetic culture media provide controlled environments for the growth and study of fungi.
Statement 3 is incorrect: Viruses lack their own metabolic machinery and depend entirely on the host cell for replication. Consequently, viruses cannot be grown in synthetic culture media alone. They require living host cells for their replication and propagation.
Q.6) Consider the following activities: (UPSC 2020)
At the present level of technology, which of the above activities can be successfully carried out by using drones?
(a) 1 only
(b) 2 and 3 only
(c) 2 only
(d) 1, 2 and 3
Answer- d
Explanation:
Statement 1 is correct: Spraying pesticides on a crop field can be successfully carried out using drones. Agricultural drones equipped with precision spraying systems can target specific areas of a crop field, delivering pesticides with accuracy and efficiency. This technology helps in reducing the amount of pesticides used, minimizing environmental impact, and optimizing crop management.
Statement 2 is correct: Some of the application of drones: Aerial photography for journalism and film
Express shipping and delivery
Gathering information or supplying essentials for disaster management
Thermal sensor drones for search and rescue operations
Geographic mapping of inaccessible terrain and locations
Building safety inspections
Precision crop monitoring
Unmanned cargo transport
Law enforcement and border control surveillance
Storm tracking and forecasting hurricanes and tornadoes.
Statement 3 is correct: Collecting breath samples from spouting whales for DNA analysis can be successfully carried out using drones. Drones equipped with specialized sampling devices can approach whales and collect exhaled breath, or blow, which contains biological material. This non-invasive method allows researchers to analyze the DNA of whales without direct physical contact.
Q.7) Consider the following pairs: (UPSC 2023)
Objects in space Description
How many pairs given above are not correctly matched?
(a) Only one
(b) Only two
(c) All three
(d) None
Answer- d
Explanation:
OPTION D IS CORRECT
Pair 1 is correct: Cepheids, also known as Cepheid Variables, exhibit periodic brightening and dimming, making them valuable cosmic yardsticks for measuring distances. The regularity of their period, which does not change over time, allows for a consistent relationship between their brightness and period. This property makes Cepheids reliable indicators of distance in astronomy.
Pair 2 is correct: A nebula is indeed a vast cloud of dust and gas in space. Some nebulae result from the remnants of dying stars, while others serve as regions where new stars are forming. The term "star nurseries" aptly describes certain nebulae that play a role in the birth of stars.
Pair 3 is correct: Pulsars are, indeed, rotating neutron stars that emit pulses of radiation at regular intervals. These intervals can range from milliseconds to seconds. Pulsars are formed from the remnants of massive stars that have undergone a supernova explosion. The collapse of the star's core results in the formation of a neutron star, and if this neutron star is observed to emit regular pulses of radiation, it is referred to as a pulsar.
Q.8) The surface of a lake is frozen in severe winter, but the water at its bottom is still liquid. What is reason? (UPSC 2011)
(a) Ice is a bad conductor of heat.
(b) Since the surface of the lake is at the same temperature as the air, no heat is lost.
(c) The density of water is Maximum at 4 degree Celsius.
(d) None of the above
Answer- c
Explanation:
Water is an unusual substance because its maximum density occurs at 4 degrees Celsius. As water cools below 4 degrees Celsius, it starts to expand and becomes less dense. When the temperature drops further, water freezes into ice. The less dense ice then floats on the denser liquid water.
In the context of the frozen lake scenario, the surface of the lake freezes because the colder air causes the water at the surface to lose heat and freeze. However, the bottom of the lake, where the water is still liquid, is insulated by the ice layer above. The ice acts as a thermal insulator, preventing further heat loss from the liquid water below. This phenomenon allows the water at the bottom of the lake to remain in a liquid state even in severe winter conditions.
Hence option c is the correct.
Q.9) With reference to ‘stem cells’, frequently in the news, which of the following statement(s) is/are correct? (UPSC 2012)
Select the correct answer using the codes given below.
(a) 1 only
(b) 2 and 3 only
(c) 3 only
(d) 1, 2 and 3
Answer- b
Explanation:
Statement 1 is incorrect: Stem cells are undifferentiated cells with the ability to differentiate into specialized cell types. While the question specifically mentions mammals, it's essential to note that stem cells are not limited to mammals and are present in various organisms.
Statement 2 is correct: Stem cells are valuable in drug discovery and testing. They can be manipulated to become specific cell types, providing a platform for testing the efficacy and safety of new drugs before clinical trials.
Statement 3 is correct: Stem cells have the potential for regenerative medicine. They can be used to replace damaged or diseased tissues and organs, offering promising avenues for treating various medical conditions. Stem cell therapies are being researched and developed for conditions such as spinal cord injuries, diabetes, and heart diseases.
Q.10) With reference to “Blockchain Technology”, consider the following statements: (UPSC 2020)
Which of the statements given above is/are correct?
(a) 1 only
(b) 2 and 3 only
(c) 2 only
(d) 1 and 3 only
Answer- d
Explanation:
Statement 1 is correct: Blockchain is indeed a public ledger that is transparent and open for inspection by anyone. It operates on a decentralized network where no single user or entity has control over the entire system. The data on the blockchain is distributed across a network of computers, ensuring transparency and security.
Statement 2 is incorrect: While blockchain technology is foundational to cryptocurrencies like Bitcoin, its applications extend beyond cryptocurrencies. Blockchain can be used to create secure and transparent ledgers for a wide range of applications, including supply chain management, healthcare records, and smart contracts.
Statement 3 is correct: Blockchain technology allows for the development of decentralized applications (DApps) without requiring centralized control or permission. Developers can create applications that leverage the fundamental features of blockchain, such as decentralization, transparency, and immutability, without the need for approval from a central authority. This characteristic is a key aspect of the blockchain's potential for fostering innovation and inclusivity.
Q.11) To meet its rapidly growing energy demand, some opine that India should pursue research and development on thorium as the future fuel of nuclear energy. In this context, what advantage does thorium hold over uranium? (UPSC 2012)
Which of the statement(s) given above is/are correct?
(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer- d
Explanation:
Statement 1 is correct: Thorium is more abundant than uranium in Earth's crust. It is three to four times more plentiful than uranium, making it a potentially attractive alternative for nuclear energy.
Statement 2 is correct: Thorium is fertile material that can undergo nuclear reactions to produce fissile material (such as uranium-233), which can be used as fuel. The energy potential of thorium is often cited as higher than that of natural uranium, as thorium-232 is more efficiently converted into fissile material in a thermal neutron spectrum.
Statement 3 is correct: The nuclear reactions involving thorium generally produce less long-lived, high-level radioactive waste compared to those involving uranium. Thorium reactors can potentially produce fewer transuranic elements, which contribute to long-term radioactivity.
Q.12) Which of the following pair(s) is/are correctly matched? (UPSC 2014)
Spacecraft Purpose
Select the correct answer using the codes given below.
(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer- b
Explanation:
Pair 1 is incorrect: Cassini-Huygens was a joint NASA-ESA mission designed for the exploration of Saturn and its moons, particularly Titan. It was launched to study Saturn's atmosphere, rings, and magnetic field, and the Huygens probe was specifically designed to land on Titan, Saturn's largest moon.
Pair 2 is correct: The Messenger spacecraft was a NASA mission specifically designed for the exploration of Mercury. It orbited the planet, mapping its surface and investigating its composition, geology, and magnetic field.
Pair 3 is correct: The Voyager 1 and Voyager 2 spacecraft were launched by NASA to explore the outer planets of our solar system. They provided invaluable data about Jupiter, Saturn, Uranus, and Neptune, as well as their moons and rings, before continuing their journey into interstellar space.
Q.13) With reference to green hydrogen, consider the following statements: (UPSC 2023)
How many of the statements given above are correct?
(a) Only one
(b) Only two
(c) All three
(d) None
Answer- c
Explanation:
Statement 1 is correct: Hydrogen internal combustion engines and hydrogen fuel cells are two distinct technologies for utilizing hydrogen as a fuel in vehicles. Hydrogen internal combustion engines burn hydrogen in a manner similar to traditional gasoline engines, while hydrogen fuel cells use a chemical process to produce electricity from hydrogen.
Statement 2 is correct: Hydrogen produced through clean methods can be blended with natural gas and injected into existing natural gas pipelines. This blended gas can be used for power generation with lower emissions compared to using natural gas alone. However, there are limits to the blending ratio, influenced by the condition and design of pipeline materials and infrastructure.
Statement 3 is correct: Fuel cell electric vehicles (FCEVs) utilize hydrogen to produce electricity through a chemical reaction in a fuel cell. They are known for their higher efficiency compared to traditional internal combustion engine vehicles and produce only water vapor and warm air as emissions, making them environmentally friendly. FCEVs differ from battery electric vehicles by generating electricity on board rather than relying solely on stored electrical energy in a battery.
Q.14) ‘Wolbachia method’ is sometimes talked about with reference to which one of the following? (UPSC 2023)
(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:
The "Wolbachia method" is a strategy employed to mitigate the transmission of viral diseases like dengue, Zika, and chikungunya through mosquitoes. This technique involves introducing Wolbachia, a bacterium, into mosquito populations to diminish their capacity to spread these diseases. Mosquitoes carrying Wolbachia, when mating with those without it, produce eggs that do not hatch or generate viable offspring. This disruption in the reproductive process helps in curtailing the population of mosquitoes that act as vectors for these viral diseases.
Q.15) 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 (UPSC 2013)
(a) Bacteria
(b) Protozoa
(c) Moulds
(d) Viruses
Answer- c
Explanation:
(a) Bacteria: Bacteria are not responsible for the production of aflatoxins. Aflatoxins are primarily associated with certain molds, particularly species of Aspergillus, such as Aspergillus flavus and Aspergillus parasiticus.
(b) Protozoa: Protozoa are single-celled eukaryotic organisms, and they are not known to produce aflatoxins. Aflatoxins are produced by fungi, not protozoa.
(c) Moulds: Aflatoxins are potent toxins produced by molds, specifically certain species of Aspergillus fungi. These molds can contaminate various crops, especially cereal grains and oilseeds, particularly in warm and humid conditions.
(d) Viruses: Viruses are not involved in the production of aflatoxins. Aflatoxin contamination is a result of fungal growth on certain crops during pre-harvest, storage, or processing stages.
Q.16) Consider the following statements: (UPSC 2021)
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- b
Explanation:
Statement 1 is incorrect: The adenovirus genome is a double-stranded DNA molecule, not single-stranded DNA. Retroviruses, on the other hand, have a single-stranded RNA genome. Adenoviruses are DNA viruses, and their genome consists of a single linear molecule of double-stranded DNA. This is different from retroviruses, which have a single-stranded RNA genome. The information provided correctly distinguishes adenoviruses as having double-stranded DNA.
Statement 2 is correct: The common cold is caused by adenoviruses, while HIV is caused by a retrovirus. Adenoviruses are indeed a common cause of respiratory infections, including the common cold. On the other hand, HIV (Human Immunodeficiency Virus) is a retrovirus. The classification of HIV as a retrovirus is accurate, and it belongs to the Lentivirus family within the retrovirus group. The mention of reverse transcriptase is also correct, as retroviruses use this enzyme to convert their RNA genome into DNA during the replication process.
Q.17) "System of Rice Intensification" of cultivation, in which alternate wetting and drying of rice fields is practised, results in : (UPSC 2022)
Select the correct answer using the code given below:
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer- d
Explanation:
OPTION D IS CORRECT
The System of Rice Intensification (SRI) involves cultivating rice with a focus on organic manure and employs the following practices:
Young seedlings planted singly at wider spacing in a square pattern.
Intermittent irrigation that keeps the soil moist but not inundated.
Frequent inter-cultivation with a weeder to actively aerate the soil.
SRI methods, including Alternate Wetting and Drying (AWD), offer several benefits compared to conventional paddy cultivation:
Option 1 is correct: SRI can increase paddy yields by 20-50%, and in some cases, up to 100%.
Option 2 is correct: It reduces the required seeds for transplanting by 60-80%. This is achieved by using young seedlings planted singly at wider spacing.
Option 3 is correct: SRI can lead to reduced electricity consumption as it allows for the reduced use of chemical fertilizers and agrichemicals. Additionally, there is a decreased need for irrigation water by 25-50%.
Regarding greenhouse gas emissions:
The information provided is correct: By implementing SRI practices, including stopping flooding and relying on organic fertilization, methane emissions are significantly reduced without offsetting increases in nitrous oxide. This leads to a reduction in net greenhouse gas emissions by approximately 30%, compared to current practices, and a more than 50% reduction in greenhouse gas emissions per kilogram of rice produced.
Q.18) Consider the following minerals: (UPSC 2013)
Which of the minerals given above is/are required by human body for the contraction of muscles?
(a) 1 only
(b) 2 and 3 only
(c) 1, 2 and 3
(d) None
Answer- c
Explanation:
OPTION C IS CORRECT:
Calcium: Role in Muscle Contraction: Calcium plays a crucial role in muscle contraction. During the process of muscle contraction, calcium ions are released from the sarcoplasmic reticulum in muscle cells. These calcium ions bind to the protein troponin, leading to a series of events that result in the contraction of muscle fibers.
Other Functions: Apart from its role in muscle contraction, calcium is essential for various physiological functions, including bone health, blood clotting, and nerve signal transmission.
Iron and Sodium:
Iron: While iron is essential for the formation of hemoglobin in red blood cells and is important for oxygen transport in the body, it is not directly involved in the contraction of muscles.
Sodium: Sodium is involved in maintaining fluid balance and is critical for nerve impulse transmission but is not directly involved in muscle contraction.
Q.19) ‘Aerial metagenomics’ best refers to which one of the following situations? (UPSC 2023)
(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-bome 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:
"Aermal metagenomics" refers to the process of collecting and analyzing DNA samples from the air or aerosol particles within a specific environment. This method involves sampling the air in a particular habitat to capture the genetic material (DNA) of microorganisms, including bacteria, viruses, fungi, and other microscopic entities. Hence option A is correct.
Q.20) Consider the following statement and identify the correct answer using the code given below: (CDS 2023)
(a) Statement 1 is correct but statement 2 is not correct.
(b) Statement 2 is correct but statement 1 is not correct
(c ) Both the statements are correct and statement 2 explains statement 1
(d) Both the statements are correct but statement 2 does not explain statement 1
Answer- c
Explanation:
Statement 1: "In a thermal power station, fuels such as oil, coal, or natural gas are used to generate electricity."
This statement is correct. In thermal power stations, fossil fuels like oil, coal, and natural gas are commonly used as energy sources to generate electricity through a thermal process.
Statement 2: "Fuels are burned to heat water and turn it into steam, which goes through a turbine, which spins and turns, generating electricity."
This statement is correct and explains the process in a thermal power station. Fossil fuels are burned to produce heat, which is used to convert water into steam. The steam is then directed through a turbine, causing it to spin, and the spinning turbine generates electricity through a connected generator.
Both statements are correct, and Statement 2 provides an explanation of the process described in Statement 1 in the context of a thermal power station.
Q.21) Which of the following statements is/are correct regarding vegetative propagation of plants? (UPSC 2014)
Select the correct answer using the code given below.
(a) 1 and 3 only
(b) 1 and 2 only
(c) 2 and 3 only
(d) 1, 2 and 3
Answer- a
Explanation:
Statement 1 is correct: Vegetative propagation involves the reproduction of plants through structures such as stems, roots, and leaves, allowing the creation of genetically identical or clonal offspring. This method ensures that the new plants share the exact genetic makeup of the parent plant.
Statement 2 is incorrect: While vegetative propagation can result in the production of disease-free plants, it does not automatically eliminate viruses. If the parent plant is infected with a virus, the propagated plants may carry the virus as well. Specific measures such as virus testing and treatment are required to ensure virus-free propagation.
Statement 3 is correct: Unlike sexual reproduction, which is often dependent on specific seasons and conditions, vegetative propagation can be carried out throughout much of the year. This flexibility allows for the continuous production of new plants, contributing to efficient and controlled propagation.
Q.22) Which of the following statements is/are correct? (UPSC 2016)
Viruses can infect
Select the correct answer using the code given below:
(a) 1 and 2 only
(b) 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer- d
Explanation:
Viruses can infect bacteria:
Viruses that infect bacteria are called bacteriophages. Bacteriophages are viruses that specifically target and infect bacterial cells. They inject their genetic material into the bacterial cell, take control of the cell's machinery, and replicate within the bacterial host.
Viruses can infect fungi:
Fungi can be susceptible to viral infections. There are viruses known as mycoviruses that infect fungi. These viruses can have various effects on fungal hosts, including altering their growth patterns, affecting pathogenicity, or causing other changes in fungal behavior.
Viruses can infect plants:
Plant viruses are a significant group of viruses that infect plants, causing various diseases. These viruses can be transmitted by vectors such as insects or through direct contact. Plant viruses can affect crop yields, plant health, and overall agricultural productivity.
Q.23) Consider the following statements regarding burning of magnesium ribbon in air : (CDS 2023)
Which of the statements given above are correct?
(a) 1 and 2 only
(b) 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer- d
Explanation:
Statement 1 is correct: When magnesium ribbon burns in air, it undergoes a chemical reaction with oxygen to form magnesium oxide (MgO), which is a white powder. The chemical equation for this reaction is: 2 Mg + O2 —--- 2MgO
Statement 2 is correct: The burning of magnesium ribbon in air is indeed an example of a combustion reaction. Combustion reactions involve the reaction of a substance with oxygen, typically producing heat and light. In this case, magnesium reacts with oxygen to form magnesium oxide, releasing energy in the form of heat and light.
Statement 3 is correct: During the combustion of magnesium, a significant amount of heat and light is produced. This is characteristic of combustion reactions where the reactants (in this case, magnesium and oxygen) undergo a rapid chemical reaction with the release of energy in the form of heat and light.
Q.24) Which of the following pairs of vitamin and disease is/are correctly matched? (CDS 2016)
Select the correct answer using the code given below:
(a) 1 only
(b) 2 only
(c) 1 and 2 only
(d) 2 and 3 only
Answer- d
Explanation:
Pair 1 is incorrect: Vitamin C deficiency leads to scurvy, a condition characterized by weakness, fatigue, swollen and bleeding gums, joint pain, and other symptoms. Vitamin C is essential for the synthesis of collagen, a protein crucial for the health of connective tissues, blood vessels, and skin.
Pair 2 is correct: Vitamin A deficiency is not associated with rickets. Rickets is primarily caused by a deficiency of vitamin D, calcium, or phosphate, and it results in the softening and weakening of bones.
Pair 3 is correct: Beriberi is associated with a deficiency of thiamine (Vitamin B1). Therefore, the correct pairing should be "Vitamin B1: Beriberi." Vitamin B, as a general term, is not specific to any particular disease. Different B vitamins are associated with various health functions and deficiencies.
Q.25) Consider the following statements: (UPSC 2017)
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- c
Explanation:
Statement 1 is correct: The primary vector for Zika virus transmission is the Aedes mosquito, particularly Aedes aegypti. This mosquito species is also a vector for other viruses, including dengue and chikungunya. Therefore, in tropical regions where these diseases are prevalent, the same mosquito species can transmit Zika virus.
Statement 2 is correct: Zika virus can be transmitted sexually from an infected person to their sexual partners. This mode of transmission was identified as a concern during the Zika virus outbreaks, and precautions were recommended to prevent sexual transmission, particularly in regions where the virus was circulating.
Q.26) Match List - I with List-II and select the correct answer from the codes given below the lists: (CAPF 2014)
List - I (Hormone) List – II (Function)
(a) A-4, B-2, C-1, D-3
(b) A-4, B-1, C-2, D-3
(c) A-3, B-2, C-1, D-4
(d) A-3, B-1, C-2, D-4
Answer- d
Explanation:
1. Aldosterone: 3. Salt-retaining hormone- Aldosterone is a hormone produced by the adrenal glands that plays a key role in regulating salt and water balance in the body. It promotes the retention of sodium and water in the kidneys.
2. Oestrogen: 1. Maintains female secondary sex characteristics- Oestrogen is a female sex hormone that is responsible for the development and maintenance of female secondary sex characteristics, including breast development and regulation of the menstrual cycle.
3. Melatonin: 2. Controls circadian rhythm- Melatonin is a hormone produced by the pineal gland that regulates the sleep-wake cycle and controls the circadian rhythm. It is involved in the synchronization of various biological processes with the day-night cycle.
4. Progesterone: 4. Sustains the pregnancy- Progesterone is a hormone that plays a crucial role in the menstrual cycle and pregnancy. It helps prepare the uterine lining for a fertilized egg and, if pregnancy occurs, sustains the early stages of pregnancy.
Q.27) Consider the following statements: (UPSC 2023)
In how many of the above action is the function of accelerometer required?
(a) Only one
(b) Only two
(c) All three
(d) None
Answer- c
Explanation:
Statement 1 is correct: Accelerometers in car crash detection systems play a crucial role in measuring the intensity of accelerations during a collision. When a crash occurs, the accelerometer detects the rapid changes in motion and sends a signal to the airbag control unit. The inflation device is then triggered, leading to the controlled release of nitrogen gas by igniting a mixture of sodium azide and potassium nitrate, ultimately inflating the airbag.
Statement 2 is correct: In laptops, accelerometers are employed to safeguard hard drives from damage caused by sudden drops. The accelerometer can detect the free fall, and in response, it triggers a protective mechanism that immediately turns off the hard drive. This prevents the reading heads from hitting the hard drive platter, reducing the risk of damage during falls.
Statement 3 is correct: Accelerometers in smartphones are versatile sensors that detect acceleration, vibration, and tilt along the three axes. Applications use this information to determine the phone's movement and exact orientation. For example, the accelerometer helps apps identify whether the phone is held in portrait or landscape orientation, and it can detect whether the phone screen is facing upward or downward.
Q.28) Which of the following statements about optical microscope is/are correct? (CAPF 2018)
3. The magnification of a microscope depends upon the length of the microscope tube.
Select the correct answer using the code given below:
(a) 1 and 2 only
(b) 1,2 and 4 only
(c) 1 and 3 only
(d) 1, 2, 3 and 4
Answer- c
Explanation:
Statement 1 is correct: In an optical microscope, the eyepiece is indeed a convex lens, but the objective is a complex lens system that typically includes multiple lenses. The objective is responsible for gathering and magnifying the initial image, while the eyepiece further magnifies the intermediate image formed by the objective.
Statement 2 is incorrect: The magnification of a microscope is influenced by various factors, including the focal lengths of both the objective and eyepiece, as well as the length of the microscope tube. However, simply increasing the focal length of the objective does not necessarily lead to an increase in magnification.
Statement 3 is correct: The magnification of a microscope is affected by the length of the microscope tube. The standard formula for the total magnification of a compound microscope is the product of the magnification of the objective and the magnification of the eyepiece. The tube length is a factor in this calculation.
Statement 4 is incorrect: The eyepiece of an optical microscope is commonly a convex lens. Convex lenses converge light rays and are used to further magnify the intermediate image formed by the objective. A concave lens would diverge light rays and is not typically used as an eyepiece in microscopes.
Q.29) Which one of the following statements explains higher mutation rate and faster evolution found in RNA virus? (CDS 2018)
(a) RNA is relatively unstable compared to DNA
(b) Virus can multiply only within the living cell of a host.
(c) Metabolic processes are absent in virus.
(d) Virus can remain latent for a long period.
Answer- a
Explanation:
The higher mutation rate and faster evolution observed in RNA viruses are primarily attributed to the fact that RNA is relatively unstable compared to DNA. RNA viruses often lack the proofreading mechanisms that DNA viruses have, leading to a higher likelihood of errors during replication. This increased mutation rate allows RNA viruses to generate diverse genetic variants more rapidly, contributing to their ability to evolve quickly and adapt to changing environments. Hence, Option a is correct.
Q.30) Consider the following pairs: (UPSC 2018)
Commonly used/consumed materials Unwanted or controversial chemicals likely to be found in them
Which of the pairs given above is/are correctly matched?
(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer- d
Explanation:
Pair 1 is correct: Lipstick—Lead. Lead has been found in certain lipsticks as a contaminant. It may be present in trace amounts, and concerns have been raised about potential health risks associated with lead exposure from cosmetics, including lipsticks.
Pair 2 is correct: Soft Drinks—Brominated vegetable oils. Some soft drinks may contain brominated vegetable oils (BVOs), which are emulsifiers. BVOs have been used to improve the stability of flavoring oils in soft drinks. However, their use has been controversial due to concerns about potential health effects, and some countries have restricted or banned their use.
Pair 3 is correct: Chinese fast food—Monosodium glutamate (MSG). Monosodium glutamate (MSG) is a common flavor enhancer used in Chinese fast food and other cuisines. While it is generally recognized as safe, there have been anecdotal reports of adverse reactions, leading to concerns about its use. However, scientific studies have not consistently supported the existence of the so-called "Chinese restaurant syndrome."
Q.31) Consider the following statements regarding cell wall composition : (NDA 2023)
Select the correct answer using the code given below:
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer- c
Explanation:
Statement 1 is correct: The cell wall of bacteria is primarily composed of peptidoglycan, which is a unique structure made up of sugar chains cross-linked by short peptides. This provides structural integrity to the bacterial cell.
Statement 2 is incorrect: The cell wall of fungi is mainly composed of a complex sugar polymer called chitin, not cellulose. Chitin provides strength and rigidity to the fungal cell wall.
Statement 3 is correct: Unlike plant cells and bacterial cells, animal cells do not have cell walls. Instead, animals have an extracellular matrix (ECM) that surrounds their cells. The ECM is composed of sugars (such as glycosaminoglycans) and proteins (such as collagen and fibronectin), providing support and facilitating cell communication.
Q.32) In plant cells (CDS 2022)
(a) Nucleus does not need a membrane but chloroplasts are surrounded by their own membrane.
(b) Nucleus and chloroplasts are surrounded separately by their own membrane.
(c) Nucleus is surrounded by membrane but chloroplasts do not need membrane.
(d) Both nucleus and chloroplasts are not surrounded by any membrane.
Answer- b
Explanation:
OPTION B IS CORRECT:
In plant cells, both the nucleus and chloroplasts are surrounded by their own distinct membranes. The nucleus is enclosed by a double membrane structure known as the nuclear envelope, which separates the genetic material (DNA) from the cytoplasm. Chloroplasts, responsible for photosynthesis, are also surrounded by a double membrane that protects the internal structures and contents of the chloroplast.
Q.33) With reference to ‘fly ash’ produced by the power plants using coal as fuel, which of the following statements is/are correct? (UPSC 2015)
Select the correct answer using the code given below.
(a) 1 and 2
(b) 2 only
(c) 1 and 3
(d) 3 only
Answer- a
Explanation:
Statement 1 is correct: Fly ash is often used as a supplementary cementitious material in the production of bricks. It can improve the properties of bricks and contribute to sustainability in construction.
Statement 2 is correct: Fly ash is commonly used as a pozzolanic material in concrete. It can replace a portion of Portland cement in concrete mixes, contributing to the reduction of greenhouse gas emissions associated with cement production and improving the durability of concrete.
Statement 3 is incorrect: While fly ash is primarily composed of silicon dioxide (SiO2) and calcium oxide (CaO), it may also contain trace amounts of other elements. The composition can vary depending on the source of coal and the combustion process. It is generally considered non-toxic, but the specific composition should be considered in environmental and health assessments.
Q.34) What is the application of Somatic Cell Nuclear Transfer Technology? (UPSC 2017)
(a) Production of biolarvicides
(b) Manufacture of biodegradable plastics
(c) Reproductive cloning of animals
(d) Production of organisms free of diseases
Answer- c
Explanation:
Somatic Cell Nuclear Transfer (SCNT) technology is primarily associated with the reproductive cloning of animals. In this process, the nucleus of a somatic cell (a cell that is not a sperm or egg cell) is transferred into an enucleated egg cell, creating an organism with the same nuclear DNA as the donor cell. This has been used to produce genetically identical animals, such as sheep, through cloning. The other options—production of biolarvicides, manufacture of biodegradable plastics, and production of organisms free of diseases—are not applications directly related to SCNT technology.
Q.35) Consider the following pairs: (UPSC 2018)
Terms sometimes seen in news Context/Topic
Which of the pairs given above is/are correctly matched?
(a) 1 and 3 only
(b) 2 only
(c) 2 and 3 only
(d) 1, 2 and 3
Answer- b
Explanation:
Pair 2 is correct: Blockchain technology—Digital/Cryptocurrency. Blockchain technology is associated with digital and cryptocurrency contexts. It is a decentralized and distributed ledger technology that underlies digital currencies like Bitcoin. It ensures secure and transparent transactions in a peer-to-peer network.
Pair 1 is incorrect: Belle II experiment is not related to Artificial Intelligence. The Belle II experiment is a particle physics experiment designed to study the properties of B mesons. It is conducted at the SuperKEKB accelerator in Japan and is not associated with Artificial Intelligence.
Pair 3 is incorrect: CRISPR–Cas9 is not related to Particle Physics. CRISPR–Cas9 is a gene-editing technology used in molecular biology and genetics. It is not associated with Particle Physics.
Q.36) Which of the following adds/add nitrogen to the soil? (UPSC 2013)
Select the correct answer using the codes given below:
(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer- c
Explanation:
Statement 1 is correct: Urea, a nitrogen-containing compound, is excreted by animals in their urine. When urea breaks down, it releases nitrogen into the soil, acting as a natural fertilizer.
Burning of coal releases various gases and pollutants, but it does not directly add nitrogen to the soil.
Statement 2 is incorrect: The combustion of coal primarily releases carbon dioxide and other compounds, contributing to air pollution rather than soil nitrogen.
Statement 3 is correct: The death and decomposition of vegetation contribute nitrogen to the soil. When plants die and decompose, the organic matter breaks down, releasing nitrogen compounds into the soil. This process is part of the natural nitrogen cycle.
Q.37) Match List - I with List - II and select the correct answer from the codes given below the lists: (CAPF 2014)
List - I (Cell type) List – II (Function)
(a) A-3, B-2, C-1, D-4
(b) A-3, B-1, C-2, D-4
(c) A-4, B-2, C-1, D-3
(d) A-4, B-1, C-2, D-3
Answer- c
Explanation:
Pair A is correct: Red Blood Cell - 4. Transport oxygen. Red Blood Cells (RBCs), also known as erythrocytes, are specialized cells that contain hemoglobin, a protein that binds with oxygen. The primary function of RBCs is to transport oxygen from the lungs to tissues and organs throughout the body.
Pair B is correct: White Blood Cell - 2. Fight infection. White Blood Cells (WBCs), or leukocytes, are part of the immune system and play a crucial role in defending the body against infections. They are involved in recognizing and attacking foreign invaders, such as bacteria, viruses, and other pathogens.
Pair C is correct: Platelets - 1. Help blood to clot. Platelets, also known as thrombocytes, are cell fragments that play a key role in blood clotting (coagulation). When there is an injury or damage to a blood vessel, platelets adhere to the site, release clotting factors, and help form a blood clot to stop bleeding.
Pair D is correct: Plasma - 3. Carrier of dissolved substances. Plasma is the liquid component of blood and serves as a carrier for various dissolved substances, including nutrients, hormones, electrolytes, and waste products. It transports these substances throughout the circulatory system.
Q.38) Consider the following statements: (CDS 2019)
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- c
Explanation:
Statement 1 is correct : This statement is in line with the concept of diffusion, where particles of matter (atoms, molecules, or ions) tend to spread out and mix with each other spontaneously. Diffusion is a natural process driven by the random motion of particles.
Statement 2 is correct: Particles of matter do experience forces between them. These forces can be attractive or repulsive, depending on the type of particles and their interactions. For example, in solids, particles are closely packed, and there are attractive forces holding them together. In gases, particles are more spread out, and there are intermolecular forces at play.
Q.39) In the context of wearable technology, which of the following tasks is/are accomplished by wearable devices? (UPSC 2019)
Select the correct answer using the code given below:
(a) 1 only
(b) 2 and 3 only
(c) 3 only
(d) 1, 2 and 3
Answer- d
Explanation:
Location identification of a person:
Wearable devices such as smartwatches often come with GPS capabilities that enable location tracking. This feature is useful for tasks like fitness tracking, navigation, and location sharing.
Sleep monitoring of a person:
Many wearable devices, especially fitness trackers and smartwatches, have sleep monitoring functionalities. They use sensors to track sleep patterns, including the duration of sleep, sleep stages, and interruptions.
Assisting the hearing impaired person:
Wearable devices, such as smart hearing aids or assistive listening devices, can assist individuals with hearing impairments. These devices use advanced technologies to enhance sound, reduce background noise, and improve the overall auditory experience for the wearer.
Hence option d is correct.
Q.40) Dengue virus is known to cause low platelet count in blood of patient by: (CDS 2016)
Select the correct answer using the code given below:
(a) 1 only
(b) 2 and 3 only
(c) 3 only
(d) 1, 2 and 3
Answer- d
Explanation:
Dengue virus can affect the bone marrow, where platelets are produced. It may interfere with the normal process of platelet production, leading to a decrease in the platelet count. This is one of the factors contributing to thrombocytopenia in dengue-infected individuals.
Dengue virus infects and replicates within endothelial cells, which line the blood vessels. The infection of these cells can lead to endothelial dysfunction, increased vascular permeability, and leakage of fluid from blood vessels. While this may not directly cause a decrease in platelet count, it contributes to the overall pathophysiology of dengue hemorrhagic fever and dengue shock syndrome.
Dengue virus is known to interact with platelets directly. The virus can bind to platelets, leading to the activation of platelets and their subsequent removal from circulation. This interaction contributes to the reduction in platelet count observed in dengue-infected individuals.
While dengue virus can cause vascular leakage and plasma leakage, leading to fluid accumulation in various tissues, the specific accumulation of platelets in the intestine is not a recognized mechanism contributing to thrombocytopenia in dengue.
Hence option d is correct.
Q.41) In the context of recent advances of human reproductive technology, “Pronuclear Transfer” is used for (UPSC 2020)
(a) fertilization of egg in vitro by the donor sperm
(b) genetic modification of sperm producing cells
(c) development of stem cells into functional embryos
(d) prevention of mitochondrial diseases in offspring
Answer- d
Explanation:
Pronuclear transfer, also known as mitochondrial replacement therapy, is a reproductive technology used to prevent mitochondrial diseases in offspring. This technique involves transferring the nucleus of a fertilized egg (zygote) from a woman with mitochondrial disease to a donor egg with healthy mitochondria. This process aims to replace the defective mitochondria in the mother's egg with healthy mitochondria from the donor egg, reducing the risk of mitochondrial diseases in the resulting offspring. Hence option d is correct.
Q.42) Consider the following statements about mixture: (CDS 2019)
Which of these statements given above is/are correct?
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
Answer- b
Explanation:
Statement 1 is incorrect: A substance cannot be separated into other kinds of matter by any physical process. A substance is a pure form of matter with specific properties, and physical processes typically do not change the identity of the substance. Chemical processes are more likely to result in the formation of new substances.
Statement 2 is correct: When a solution of sodium chloride in water (saltwater) is subjected to the physical process of evaporation, the water evaporates, leaving behind the dissolved sodium chloride as solid salt. This is a physical separation process based on differences in volatility.
Q.43) In the context of hereditary diseases, consider the following statements: (upsc 2021)
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- c
Explanation:
Statement 1 is correct: Mitochondrial replacement therapy (MRT) is a form of reproductive in vitro fertilization (IVF) that involves replacing a woman's mitochondrial DNA (mt-DNA) with a donor's healthy one. MRT includes different techniques such as spindle transfer (ST), pronuclear transfer (PNT), or polar body transfer (PBT). Pronuclear transfer is a specific approach within MRT carried out after fertilization, where two zygotes are cultured in vitro.
Statement 2 is correct: Mitochondria are organelles that contain DNA in circular form, and in animals, they are the only organelles, in addition to the nucleus, that contain DNA and genes. Sperm contain a very low number of mitochondria and mitochondrial genes. Therefore, in offspring, mitochondrial genes are inherited from the mother, and a father with a mitochondrial gene defect cannot transmit the disease to his offspring.
Q.44) Consider the following: (UPSC 2022)
Which of the above are built on top of open-source digital platforms?
(a) 1 and 2 only
(b) 2, 3 and 4 only
(c) 1, 3 and 4 only
(d) 1, 2, 3 and 4
Answer- d
Explanation:
"Closed source" software has source code that only the person, team, or organization who created it maintains exclusive control over. In contrast, open-source software (OSS) is characterized by source code that is accessible to anyone, allowing inspection, modification, and enhancement by the community.
Several public services in India, such as Aadhaar, GSTN, and DigiLocker, utilize Free and Open Source Software (FOSS) building blocks. Additionally, various government solutions, including Digilocker, Diksha, Aarogya Setu, and the Covid-19 vaccination platform CoWIN, have been developed on top of open-source digital platforms.
Q.45) Consider the following statements: (CAPF 2022)
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- a
Explanation:
Statement 1 is correct: Aluminium powder is indeed used as a component in solid rocket propellants. When ignited, it undergoes a combustion reaction with an oxidizer, releasing energy and producing gases that propel the rocket.
Statement 2 is incorrect: Solid rocket engines generally have lower specific impulse (thrust per amount of fuel burned) compared to liquid rocket engines. Liquid rocket engines allow for better control of combustion and can be shut down and restarted, providing more flexibility in mission profiles. Solid rocket engines, once ignited, burn until their propellant is depleted, and they cannot be easily controlled or shut down.
Q.46) Which one of the following statements regarding insulin hormone is correct? (NDA 2023)
(a) Insulin is a protein hormone which is not produced in human body.
(b) Insulin is a steriod hormone which is produced in human body.
(c) Insulin is a cholesterol-driven hormone given to human
(d) Insulin is a protein hormone which is produced in human body.
Answer- d
Explanation:
Insulin is a peptide hormone, specifically a protein hormone, that is produced by the beta cells of the pancreas in the human body. It plays a crucial role in regulating blood glucose levels by facilitating the uptake of glucose by cells for energy storage and utilization.
Hence option d is correct.
Q.47) Aspartame is an artificial sweetener sold in the market. It consist of amino acids and provides calories like other amino acids. Yet, it is used as a lowcalorie sweetening agent in food items. What is the basis of this use? (UPSC 2011)
(a) Aspartame is as sweet as table sugar, but unlike table sugar, it is not readily oxidized in human body due to lack of requisite enzymes.
(b) When aspartame is used in food processing, the sweet taste remains, but it becomes resistant to oxidation.
(c) Aspartame is as sweet as sugar, but after ingestion into the body, it is converted into metabolites that yield no calories.
(d) Aspartame is several times sweeter than table sugar, hence food items made with small quantities of aspartame yield fewer calories on oxidation.
Answer- d
Explanation
Aspartame is a high-intensity sweetener that is several times sweeter than table sugar (sucrose). Because it is much sweeter, only small amounts of aspartame are needed to achieve the desired level of sweetness in food and beverages. Due to its high sweetness potency, food items made with aspartame can provide the sweet taste without adding a significant amount of calories.
The metabolism of aspartame involves the breakdown of its components, aspartic acid and phenylalanine, which are amino acids. However, the amount of these amino acids released during metabolism is small, and they contribute minimal calories compared to the sweetness provided. Therefore, even though aspartame contains amino acids, it is used as a low-calorie sweetening agent because the small quantities used contribute fewer calories on oxidation than an equivalent sweetness provided by table sugar.
Q.48) When calcium metal reacts with sulphuric acid, the reaction stops after a short while. Why? (CAPF 2021)
(a) The reaction of calcium with sulphuric acid is not feasible at room temperature
(b) Formed calcium sulphate is insoluble in water and covers the calcium metal, preventing it from reacting any further
(c) Formed calcium sulphate requires two molecules of water to crystallize as gypsum
(d) Formed calcium sulphate is unstable
Answer- b
Explanation:
When calcium metal reacts with sulphuric acid, it forms calcium sulphate as one of the products. Calcium sulphate is sparingly soluble in water and tends to precipitate out. The formed calcium sulphate layer covers the surface of the calcium metal, preventing it from further reacting with sulphuric acid. This layer acts as a barrier and hinders the continuation of the reaction. As a result, the reaction stops after a short while. Hence option b is correct.
Q.49) Consider the following statements about Tincture of Iodine : (CDS 2022)
How many of the above statements is/are correct?
(a) 1
(b) 2
(c) 3
(d) None
Answer- c
Explanation:
Statement 1 is correct: Tincture of Iodine is commonly used as an antiseptic solution. It contains iodine, which has antiseptic properties, making it effective in killing or inhibiting the growth of microorganisms, including bacteria and fungi.
Statement 2 is correct: Tincture of Iodine is prepared by dissolving iodine crystals in a mixture of alcohol and water. The alcohol helps in solubilizing iodine, allowing it to form a solution that can be easily applied.
Statement 3 is correct: Tincture of Iodine typically has a low concentration of iodine. This is intentional to ensure that it is safe for topical application on the skin. Higher concentrations of iodine can be irritating or damaging to the skin.
Q.50) Brominated flame retardants are used in many household products like mattresses and upholstery. Why is there some concern about their use? (UPSC 2014)
Select the correct answer using the code given below.
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
Answer- c
Explanation:
Statement 1 is correct: Brominated flame retardants are known for their environmental persistence. They resist degradation, and this characteristic raises concerns because it means they can persist in the environment for a long time, potentially leading to bioaccumulation.
Statement 2 is correct: Brominated flame retardants can accumulate in the tissues of living organisms, including humans and animals. This bioaccumulation occurs through exposure to products containing these flame retardants. Once absorbed, they can persist in the body and may have potential health implications.
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