Miscellaneous: UPSC Previous Year Questions (Science and Technology)

Explanation

Option (b) is correct: Cluster bean commonly known as guar has traditionally been utilized in India as a vegetable and animal feed. Guar gum is widely used in the oil and gas industry particularly in hydraulic fracturing (fracking) for shale gas extraction. It acts as a thickening agent in fracking fluids, helping to carry proppants (like sand) into fractures in the shale rock to keep them open and allow gas to flow. India is one of the largest producers of guar in the world and the demand for guar gum surged due to its use in shale gas extraction especially in the United States.

Option (a),(c) and (d) are incorrect:

Guar seeds are primarily known for their gum content and not oil. It has applications in various industries (food, pharmaceuticals, textiles, etc.) but there is no widespread use of guar seed oil in the manufacture of biodegradable plastics. Traditionally guar leaves have been consumed as a vegetable but their medicinal properties particularly as antihistamines is not well-documented. Guar seeds are not a significant source of biodiesel. It is not commercially significant or widely recognized as a high-quality biodiesel source.

Explanation

The Agni-IV is an intermediate-range ballistic missile developed by India’s Defence Research and Development Organisation (DRDO)

Statement 1 is correct: The Agni-IV is designed as a surface-to-surface missile, capable of being launched from the ground to strike terrestrial targets. It enhances India’s strategic strike capabilities. Statements 2 is incorrect: The Agni-IV utilizes a two-stage solid propellant system, not liquid propellant. Solid propellants offer advantages such as easier handling and longer storage life, which are beneficial for ballistic missiles. Statements 3 is incorrect: The Agni-IV has a range of around 4,000 km and is capable of carrying a payload of up to one tonne, including nuclear warheads. A range of 7,500 km would classify the missile as an intercontinental ballistic missile (ICBM), but the Agni-IV is categorized as an intermediate-range ballistic missile (IRBM).

Explanation

Photosynthesis is the process by which green plants, algae, and certain bacteria convert light energy into chemical energy, producing glucose and releasing oxygen. The functions of the chlorophyll, a green pigment, are related to the transformation of inefficient solar energy into useful chemical energy. During photosynthesis, plants capture light energy (free energy) and convert it into chemical energy, storing it as potential energy in the bonds of glucose molecules. This stored energy can later be used by the plant for various metabolic processes. 6H₂O + 6CO₂C₆H₁₂O₆ + 6O₂

Explanation

Vegetative propagation is a fascinating form of asexual reproduction where new plants grow from specialized vegetative parts like stems, roots, or leaves rather than seeds.

Statement 1 is correct: Vegetative propagation is a process in which new plants are grown from the vegetative parts of the parent plant. As this method does not involve sexual reproduction, the offspring are genetically identical to the parent, creating a clonal population. This technique ensures uniformity among the progeny, making it particularly useful for preserving desirable traits in cultivated plants.

Statement 2 is incorrect: Standard methods of vegetative propagation generally do not eliminate viruses rather they often perpetuate viral infections because the new plants are exact genetic clones of the infected parent plant.

Statement 3 is correct: Unlike seed-based propagation, which is often dependent on specific seasons, methods like cuttings, layering, or tissue culture can be carried out continuously as long as the required conditions and resources are provided. Vegetative propagation can typically be practiced year-round, particularly in controlled environmental settings. This adaptability enables the consistent production of new plants.

Explanation

Transgenic crops are developed by introducing foreign genes into a plant’s genome to confer new traits, such as pest resistance or improved nutritional content.

Statement 1 is incorrect: Budding and grafting are traditional horticultural techniques used to propagate plants. In grafting, tissues from one plant are inserted into those of another so that the two sets of vascular tissues may join together. These methods do not alter the genetic makeup of the plants.

Statement 2 is correct: Cytoplasmic male sterility (CMS) refers to the complete or partial inability of plants to produce functional male gametes. Male Sterility prevents the plant from producing viable pollen, thereby rendering it incapable of self-fertilization. CMS systems are extensively used in hybrid crop production because they simplify the process of controlling male sterility, eliminating the need for manual emasculation during cross-breeding. This enhances efficiency and consistency in hybrid seed production.

Statement 3 is correct: Gene silencing refers to techniques used to suppress the expression of specific genes within an organism. In the context of transgenic crops, methods such as RNA interference (RNAi) are employed to downregulate or silence target genes, thereby conferring desired traits like pest resistance or delayed fruit ripening. One notable example of gene silencing in India is the development of Bt Cotton using RNA interference (RNAi). In Bt cotton, a gene from the soil bacterium Bacillus thuringiensis (Bt) is introduced to produce proteins that are toxic to cotton bollworm pest.

Explanation

Statement 1 is correct: Maize is a primary source for commercial starch production. Through a wet milling process, maize kernels are separated into components such as starch, oil, protein, and fiber. The extracted starch is utilized in multiple industries, including food, paper, and textiles.

Statement 2 is correct: Maize oil, also known as corn oil, can be used as a raw material for biodiesel production. Through a chemical process called transesterification, the oil reacts with short-chain alcohols such as methanol or ethanol, using a catalyst to produce biodiesel efficiently.

Statement 3 is correct: Maize plays a significant role in the production of various alcoholic beverages. Its starch is broken down into sugars, which are subsequently fermented to produce alcohol. This process is crucial in crafting drinks like bourbon whiskey, which traditionally uses a mash containing at least 51% maize.

Explanation

The animal kingdom is broadly classified into different phyla based on structural and functional characteristics.

Option (a) is correct: Arthropoda is the largest phylum in the animal kingdom, including organisms with jointed appendages, segmented bodies, and exoskeletons made of chitin. The phylum is further divided into several subphyla, two of which are:

Chelicerata (includes arachnids like mites, spiders, and scorpions) and Crustacea (includes crabs and other aquatic arthropods). The subphylum Chelicerata (e.g., spiders, scorpions) has two body regions, no antennae, four pairs of legs, and uses chelicerae for feeding, adapted to terrestrial life with book lungs. Crustacea (e.g., crabs, lobsters) has three body regions, two pairs of antennae, gills for respiration, and compound eyes, primarily adapted to aquatic habitats with specialized mandibles. Hence, the crab does not belong to the same class as the mite, spider, and scorpion.

Explanation

A food chain represents the transfer of energy through a series of organisms, starting from green plants (primary producers) and progressing through successive consumers. For example: Grasses Grasshopper Frog Snake Hawk/ Eagle. Each step in the food chain is referred to as a trophic level, indicating the organism’s position in the chain. Food chains begin with producers and end with top carnivores. In marine ecosystems, phytoplankton serve as primary producers. These include:

Diatoms (unicellular algae) Coccolithophores (unicellular eukaryotic protists), Cyanobacteria (blue-green algae such as Synechococcus, Prochlorococcus, Nostoc, and Spirogyra) Dinoflagellates (flagellated protists) Crustaceans, a group of arthropods that includes crabs, lobsters, shrimp, krill, and barnacles, feed on diatoms. In turn, herrings, a type of fish, consume crustaceans, completing this segment of the marine food chain.

Explanation

Statement 1 is correct: PV technology directly converts sunlight into electricity using semiconductor materials like silicon. When sunlight hits the PV cells, it excites electrons, generating Direct Current (DC) electricity. This is a clean and efficient method of harnessing solar energy for electricity. Solar thermal systems use solar collectors to capture the Sun’s heat. This heat is typically used to produce steam, which drives turbines connected to generators, producing electricity. Solar thermal is often used in large-scale power plants and heating systems.

Statement 2 is incorrect: PV systems initially produce Direct Current (DC), which is then converted to Alternating Current (AC) using inverters for compatibility with the electrical grid and household appliances. Solar Thermal systems generate heat, which is used to produce AC electricity through conventional turbines and generators.

Statement 3 is incorrect: India has established manufacturing capabilities for both Solar Thermal and Photovoltaic technologies. The country is expanding its PV manufacturing capacity, aiming to become self-sufficient and reduce reliance on imports.

Explanation

Hibernation is a survival strategy employed by various animals to endure periods of reduced food availability and harsh environmental conditions, typically during winter. This state is characterized by significantly lowered metabolic rates, decreased body temperatures, and reduced physiological activities. Many bat species enter hibernation during colder months when their insect prey becomes scarce. During hibernation, bats can experience a substantial drop in body temperature and significant reduction in metabolic rate. They often hibernate communally in caves, mines, or other sheltered locations that provide stable, cold environments. Bears undergo a form of hibernation known as torpor, which is less extreme than the hibernation observed in smaller mammals. During torpor, bears experience a moderate decrease in body temperature and metabolic rate. They remain in dens throughout the winter months, surviving on stored body fat. Notably, female bears give birth during this period and are capable of nursing their cubs without leaving the den. Species such as ground squirrels and certain mice enter deep hibernation during which they significantly lower their body temperatures and metabolic rates. This state allows them to conserve energy and survive extended periods without food. Rodents often prepare for hibernation by accumulating fat reserves and creating insulated nests or burrows to protect against the cold.