Science and Technology: UPSC Previous Year Questions (Prelims)

Explanation

Lead poisoning is a toxic condition caused by the accumulation of lead in the body, typically through exposure to contaminated air, water, soil, or consumer products. It affects multiple organ systems, particularly the nervous system, and can lead to severe health issues such as cognitive impairment, developmental delays, and organ damage.

Option 1 and 3 are correct: Even after the stricter regulations, major sources of lead pollution include mining, smelting, manufacturing, and recycling, with the production of lead-acid batteries for automobiles accounting for over three-quarters of global lead usage. Other common sources of lead poisoning include lead-based paint, contaminated soil, children’s toys and jewelry, drinking water from lead pipes, workplace and hobby hazards (such as mining and smelting), lead-glazed ceramics, pottery, leaded crystal, imported candy, and mini blinds.

Option 2 and 4 are incorrect:

Pens and pencils are incorrect as modern pencils mostly contain graphite, not lead, and pens use regulated ink formulations. Hair oils and cosmetics are incorrect because most cosmetic products are strictly regulated to prevent lead contamination, with only rare exceptions in some traditional items.

Explanation

Cowpea, green gram, and pigeon pea are all versatile crops used in various agricultural practices. Cowpea is a leguminous plant that serves as a pulse, fodder, and green manure. Its seeds are harvested for food, while the plant’s leaves and stems are used as fodder for livestock. Additionally, cowpea is effective as green manure due to its ability to fix nitrogen in the soil, enhancing soil fertility. Green gram, primarily grown for its seeds, is mainly used as a pulse and also as fodder for animals. Although it can contribute to soil health, it is less frequently used as green manure compared to other legumes. Pigeon pea is similarly multifunctional, used as a pulse for consumption, fodder for livestock, and green manure to enrich soil. It plays a crucial role in improving soil fertility by fixing nitrogen. Overall, all three crops serve important roles in sustainable agriculture, with cowpea and pigeon pea being more widely used as green manure than green gram. Note: However, UPSC didn’t consider Pigeon Pea as suitable fit and marked option (a) as correct

Explanation

Statement 1 is correct: Thorium composes 0.0006% of the earth’s crust whereas Uranium composes 0.00018% of the earth’s crust, where a substantial amount of Uranium is found in dissolved seawater. Thus, Thorium(Th) is comparatively far more abundant in nature than uranium(U).

Statement 2 is correct: Uranium-233, produced from thorium, is generally considered to have higher energy output compared to natural uranium, with estimates suggesting it could produce significantly more energy per unit mass, though the exact ratio can vary depending on reactor design and conditions.

Statement 3 is correct: Thorium-based reactors generate less long-lived radioactive waste compared to uranium-based reactors. The waste from thorium has a lower proportion of transuranic elements like plutonium, which are highly radioactive and pose disposal challenges."

Explanation

Biologists studying various forms of life on Earth have identified a common characteristic among all living organisms. The matter within every living organism on Earth primarily consists of four chemical elements: hydrogen, oxygen, carbon, and nitrogen.

Option (b) is correct: Carbon, hydrogen, and nitrogen are the elements that were primarily responsible for the origin of life on Earth. These elements are fundamental in the formation of organic compounds, such as proteins, nucleic acids, and lipids, which are essential for life. The combination of carbon, hydrogen, and nitrogen forms the basis of amino acids, nucleotides, and other critical biomolecules involved in the origin of life on Earth.

Explanation

Capillarity (or capillary action) is the ability of a liquid to flow in narrow spaces, such as thin tubes or porous materials, without the assistance of external forces and even against gravity. It occurs due to the cohesion (attraction between liquid molecules) and adhesion (attraction between the liquid and solid surface), along with surface tension.

Statement 1 is correct: The oil in the wick of a lamp rises due to the capillary action of threads in the wick. Absence of capillarity would certainly make it difficult to use Kerosene lamps.

Statement 2 is incorrect: There is no capillary action in using a straw to consume the soft drink as the consumer applies additional pressure from the mouth to consume the soft drink.

Statement 3 is correct: A blotting paper soaks ink by the capillary action of the pores in the blotting paper. The blotting paper will not be useful without the capillarity phenomenon.

Statement 4 is correct: The root-hairs of plants draw water from the soil through capillary action. Therefore absence of capillarity phenomenon would adversely affect the growth of trees.

Explanation

DNA Sequencing means determining the order of the four chemical building blocks - called "bases" - that make up the DNA molecule. This sequence informs scientists the kind of genetic information that is carried in a particular DNA segment.

Statement 1 is correct: Pedigree analysis is the examination of a particular trait that is inherited from generation to generation. It helps in understanding the inheritance pattern of that trait and determining whether it is dominant or recessive. A thorough pedigree analysis using pedigree files received via DNA sequencing from the relevant breed organisations will certainly help in interpreting the pattern of inheritance of a livestock.

Statement 2 is correct: Mapping genes allows researchers to identify genetic variations associated with diseases. This understanding facilitates the development of targeted therapies and personalized medicine approaches.

Statement 3 is incorrect: Knowledge of gene positions enables the identification of genes responsible for disease resistance. This information can be utilized to breed or genetically engineer animals that are more resilient to specific diseases. However UPSC has not recognised it as completely true as if this application of DNA sequencing is still under development.

Explanation

Any substance that can inhibit the formation of unstable molecules known as free radicals, which harm DNA, cell membranes, and other components of cells, is referred to as an "antioxidant." Free radicals grab electrons from other molecules in order to complete their electron complement, which causes those molecules to suffer damage. Regular consumption of fresh fruits and vegetables is recommended because they are rich sources of antioxidants. Antioxidants play a crucial role in maintaining health and promoting longevity by neutralizing free radicals produced during metabolism. Free radicals are unstable molecules that can damage cells, proteins, and DNA, contributing to ageing and various diseases. By donating electrons, antioxidants stabilize free radicals, thereby preventing cellular damage and supporting overall health.

Explanation

Option (a) is correct: Bluetooth operates in the 2.4 GHz Industrial, Scientific, and Medical (ISM) band. Wi-Fi, depending on the standard, operates in the 2.4 GHz and/or 5 GHz bands.

Option (b) is incorrect: Bluetooth is typically used for short-range communication, forming Personal Area Networks (PANs), such as connecting peripherals like headphones or keyboards to a computer. Wi-Fi is used for Wireless Local Area Networks (WLANs), providing network connectivity within a local area like a home or office. Neither Bluetooth nor Wi-Fi is typically used for Wireless Wide Area Networks (WWANs), which cover broader areas and are usually associated with cellular networks.

Option (c) is incorrect: Bluetooth does not require a direct line of sight between devices as it can transmit data through obstacles like walls or furniture, though the presence of obstacles can affect the range and quality of the connection. Wi-Fi also does not require line of sight and can cover greater distances than Bluetooth, with its signals capable of passing through walls and other obstructions, though signal strength may degrade with obstacles.

Option (d) is incorrect: Since statement (b) is incorrect the fourth statement ("The statements (a) and (b) given above are correct in this context") is also incorrect.

Explanation

A VPN is a technology that creates a secure, encrypted connection(computer network) over a public internet network (such as the internet) to allow remote users to access their organization’s private network securely. It ensures that data transmitted between the user and the organization’s network is protected from interception or unauthorized access. A VPN encrypts the data transmitted between the user’s device and the VPN server. This ensures that even if the data is intercepted it cannot be read by unauthorized parties. They allow users to bypass geo-restrictions and access content that may be blocked in their region (e.g., streaming services, websites, or social media platforms).

Explanation

Artificial satellites are launched into orbit for a variety of purposes, including communications, navigation, Earth imaging, weather observation, and scientific study. In satellites, humans typically experience a sense of weightlessness because the net force acting on our body is practically zero. This is due to the satellite’s centrifugal force, which cancels out the size of the earth’s gravitational pull. On the other hand, the earth’s gravitational pull is required for the satellite to continuously change its direction, giving acceleration for the satellite’s direction-changing process.