Science and Technology: UPSC Previous Year Questions (Prelims)

Explanation

Short-Range Devices (SRDs) are communication technologies designed for limited-distance operations, typically within a few meters to a few hundred meters.

Option 1 is correct: CCTV systems use video cameras to transmit signals to specific monitors for surveillance purposes. The transmission range of CCTV systems is generally confined to the premises being monitored, making them short-range by design.

Option 2 is correct: RFID employs electromagnetic fields to automatically identify and track tags attached to objects. They are typically short-range, with passive RFID tags readable from up to a few meters and active tags extending up to 100 meters.

Option 3 is correct: WLANs enable wireless network communication within a localized area, such as a home or office, using high-frequency radio waves. The effective range of WLANs is usually within 100 meters, categorizing them as short-range communication technologies.

Explanation

A solar storm is a disturbance on the Sun that can release a burst of energy and particles into space. These eruptions, such as solar flares and coronal mass ejections, can impact Earth by disrupting communication systems, damaging satellites, and even causing power outages. Statements 1 and 7 are correct: These solar explosions propel bursts of particles and electromagnetic fluctuations into Earth’s atmosphere that could lead to the malfunction of satellites, which might impact high-frequency communication blackouts, satellite anomalies, GPS scintillations, airline communication.

Statement 2 is incorrect: Solar storms affect the Earth’s magnetosphere and ionosphere but do not directly cause tsunamis, which are triggered by seismic activity, underwater landslides, or volcanic eruptions.

Statement 3 is correct: The solar explosions propel bursts of particles and electromagnetic fluctuations into Earth’s atmosphere that could destroy transformers in power systems.

Statement 4 is correct: Energy, radiation and high energy particles emitted by solar flares can trigger intense lights in the sky, called Auroras.

Statement 5 is incorrect: Flares are electromagnetic radiation bursts rather than actual fires. They won’t start forest fires as a result. While they release high-energy radiation, it does not directly ignite fires on Earth.

Statement 6 is correct: Particles from a CME can potentially collide with a satellite’s critical electronics, causing the satellite’s systems to malfunction.

Explanation

The Fractional Orbital Bombardment System (FOBS) is a missile technology designed to place a nuclear warhead into a partial Earth orbit before deorbiting to strike a target. Unlike intercontinental ballistic missiles (ICBMs), FOBS takes an unpredictable orbital path, bypassing traditional radar systems and potentially striking from unexpected directions, such as via the South Pole. Originally developed by the Soviet Union in the 1960s, FOBS was tested with the R-36ORB missile but later abandoned under arms control treaties like SALT II and the Outer Space Treaty. Recent reports indicate renewed interest, with countries like China reportedly testing FOBS integrated with hypersonic glide vehicles. Its capability to evade missile defenses has raised global security concerns and spurred advancements in countermeasures. ICBM Radar Beam Launch site FOBS FOBS Apogee ~150 km ~1200 km Target Early-warning Radar Fig: Fractional Orbital Bombardment System (FOBS)

Explanation

A biofilm is a collection of microbial cells that are encased in a polysaccharide-based matrix and are permanently attached to a surface (i.e., cannot be removed by gentle rinsing). Microorganisms that form biofilms include bacteria, fungi, and protists. Noncellular materials such as mineral crystals, corrosion particles, clay or silt particles, or blood components, depending on the environment in which the biofilm has developed, may also be found in the biofilm matrix.

Statement 1 is correct: Biofilms may form on a wide variety of surfaces, including living tissues, food and food processing surfaces, indwelling medical devices (devices in the body like catheters, heart valves), human and animal tissue, industrial or potable water system piping, or natural aquatic systems.

Statement 2 is correct: Biofilms are a significant concern in the food industry, forming on surfaces such as cutting boards, conveyor belts, and food packaging equipment. Contaminated biofilms can lead to foodborne illnesses caused by pathogens like Listeria monocytogenes, Salmonella, and Escherichia coli.

Statement 3 is correct: Microorganisms in biofilms are significantly more resistant to antibiotics compared to planktonic (free-floating) cells because:

The EPS (extracellular polymeric substance) matrix acts as a barrier, limiting antibiotic penetration. Cells within biofilms have reduced metabolic activity, making them less susceptible to antibiotics targeting active processes. Some bacteria within biofilms can exchange antibiotic resistance genes via horizontal gene transfer. This resistance complicates treatment, especially in chronic infections such as cystic fibrosis, where Pseudomonas aeruginosa biofilms are common.

Explanation

Some species of ants such as leafcutter ants (of genus Atta and Acromyrmex) are well-known for cultivating fungi. These ants cut leaves and use them to grow fungi in specialized underground gardens. The fungi serve as the primary food source for the ant colony. This relationship between ants and fungi is a classic example of mutualism where both species benefit. The ants provide the fungi with a controlled environment and a constant supply of plant material while the fungi provide the ants with a nutritious food source. Leafcutter ants are primarily found in Central and South America,

Explanation

Mitochondrial diseases are a group of genetic disorders caused by dysfunction in the mitochondria, the cell’s energy-producing structures.

Statement 1 is correct: Mitochondrial Replacement Therapy (MRT) is an advanced reproductive technique designed to prevent the transmission of mitochondrial diseases from mother to child. MRT involves replacing defective mitochondria in an egg or embryo with healthy mitochondria from a donor. This can be achieved through methods such as:

Spindle Transfer: Performed before fertilization, where the nuclear DNA from the mother’s egg is transferred to a donor egg with healthy mitochondria, followed by fertilization. Pronuclear Transfer: Conducted after fertilization, where the pronuclei (genetic material) from a fertilized egg are transferred into a donor zygote that has healthy mitochondria. These techniques aim to ensure that the resulting child inherits healthy mitochondria, thereby preventing mitochondrial diseases.

Statement 2 is correct: A child inherits mitochondrial diseases entirely from the mother and not from the father. Mitochondria are unique organelles within cells that have their own DNA, known as mitochondrial DNA (mtDNA). Unlike nuclear DNA, which is inherited from both parents, mtDNA is typically inherited exclusively from the mother. This is because the mitochondria in the sperm are usually destroyed or degraded after fertilization, and thus do not contribute to the embryo’s mitochondrial pool. Consequently, if a mother has a mitochondrial disease (caused by mutations in her mtDNA), there is a risk that she can pass it on to her children, while fathers do not pass on mtDNA to their offspring, and thus do not transmit mitochondrial diseases.

Explanation

ACE2 (Angiotensin Converting Enzyme 2) is a protein on the surface of many cell types and tissues, including the lungs, heart, blood vessels, kidneys, liver, and gastrointestinal tract. It serves as the entry point for certain coronaviruses, notably SARS-CoV-2, the virus responsible for COVID-19. The virus’s spike protein binds to the ACE2 receptor, facilitating its entry into host cells and leading to infection.

Explanation

Adenoviruses are non-enveloped, double-stranded DNA viruses that infect a wide range of hosts, including humans. They are known for their ability to efficiently infect various cell types. A retrovirus is a virus that uses RNA as its genetic material. Upon infection with a retrovirus, a cell converts the retroviral RNA into DNA, which in turn is inserted into the DNA of the host.

Statement 1 is incorrect: Adenoviruses possess linear, double-stranded DNA genomes whereas retroviruses have single-stranded RNA genomes. Upon infecting a host cell, retroviruses use the enzyme reverse transcriptase to convert their RNA into double-stranded DNA, which is then integrated into the host’s genome.

Statement 2 is correct: Adenoviruses are known to cause respiratory illnesses, including symptoms similar to the common cold. AIDS (Acquired Immunodeficiency Syndrome) is caused by the Human Immunodeficiency Virus (HIV), which is a retrovirus.

Explanation

A Recombinant Vector Vaccine is a vaccine that uses a genetically modified virus or bacterium as a carrier to deliver pathogen-specific genes, triggering an immune response.

Statement 1 is correct: Recombinant vector vaccines are developed using genetic engineering to insert genes encoding antigens into harmless viruses or bacteria, which serve as vectors. These vectors deliver the genetic material into the body, enabling the expression of target antigens and triggering an immune response against the pathogen. Examples include viral vector vaccines like Oxford-AstraZeneca (ChAdOx1 nCoV-19) and Sputnik V for COVID-19.

Statement 2 is correct: Both bacteria (such as Salmonella) and viruses (such as adenoviruses and vesicular stomatitis virus) can be used as vectors to deliver genetic material into host cells to stimulate an immune response.

Explanation

Astronomical distances are measured in light-years to effectively express the vast distances in space using a consistent and universal unit. A light-year represents the distance light travels in one year in a vacuum, which is approximately 9.46 trillion kilometers (5.88 trillion miles). Astronomers calculate the distances of stars and other celestial objects in the time it takes for light to reach us since estimating distances in miles or kilometres is inadequate on the cosmological scale. Since the speed of light is known to be constant throughout the universe and for high precision, astronomical distances are expressed in terms of light-years. The fastest light can move is in vacuum.