Science and Technology: UPSC Previous Year Questions (Prelims)

Explanation

Statement 1 is correct: The sweet orange plant is propagated through the grafting technique where a scion (shoot) from a desired sweet orange tree is grafted onto the rootstock of a compatible plant. This ensures the plant retains the desired traits such as high fruit quality and disease resistance.

Statement 2 is correct: The jasmine plant is commonly propagated by layering technique, particularly mound layering or air layering. This method involves bending a healthy branch to the ground or wrapping it with moist materials to encourage root development, which helps maintain the plant’s genetic identity and growth potential.

Explanation

Genetic disorders are caused by abnormalities in an individual’s DNA, inherited from parents or arising from mutations. They can affect structure, function, or production of proteins. Types include single-gene disorders (e.g., cystic fibrosis), chromosomal disorders (e.g., Down syndrome), and multifactorial disorders (e.g., diabetes), impacting health, development, or metabolism.

Option (d) is correct:

Color blindness is a sex-linked recessive disorder carried on the X chromosome. In the above case, the woman suffers from color blindness but her husband does not. Woman’s Genotype: Since the woman has color blindness, her genotype must be X^cX^c (as both X chromosomes carry the color blindness allele). Man’s Genotype: Since the man does not have color blindness, his genotype must be XY (as the Y chromosome does not carry the color blindness gene). Children’s Genotypes:

Son: A son inherits his X chromosome from his mother and his Y chromosome from his father. Since the mother has the X^c chromosome, the son’s genotype will be X^cY, meaning the son will suffer from color blindness. Daughter: A daughter inherits one X chromosome from her mother and one X chromosome from her father. Since the father has a normal X chromosome, the daughter’s genotype will be X^cX. Since color blindness is a recessive trait, the daughter will be a carrier but won’t suffer from color blindness.

Explanation

The flying fox is a type of megabat belonging to the Pteropus genus in the Pteropodidae family. These large bats have wingspans ranging from 1.5 to 1.8 meters and are known for their fox-like faces, which is how they got their name. Flying foxes are found mostly in tropical and subtropical areas, particularly in coastal regions and tropical forests of India. As frugivores, they primarily feed on fruit and play a vital role in pollination and seed dispersal, contributing to the health of their ecosystems. Unlike smaller insect-eating bats, flying foxes do not rely on echolocation. Instead, they use their sharp vision to navigate and find food. This makes them unique compared to other bat species.

Explanation

Salamander-Python-Kangaroo sequence follows a correct evolutionary progression:

Salamanders are amphibians to the class Amphibia.

Amphibians evolved from fish and are characterized by their ability to live both in water (as larvae) and on land (as adults). Pythons are reptiles in the class Reptilia which have evolved from amphibians. Reptiles are vertebrates with dry skin, and they lay eggs on land (as opposed to amphibians, which generally need water for reproduction). Kangaroos are mammals, specifically marsupials in the class Mammalia. Mammals evolved from reptiles. Kangaroos are one of the few mammals that give birth to underdeveloped offspring, which then continue to develop in a pouch.

Explanation

The giant panda (Ailuropoda melanoleuca) belongs to the Ursidae family, which includes all modern bears such as grizzly, polar, and black bears. Though classified as carnivores, giant pandas are mainly herbivores, with bamboo making up to 99% of their diet. They have a unique "thumb" (modified wrist bone) that helps them grasp bamboo. These solitary creatures are recognized by their black and white fur and have a slow metabolism due to their low-calorie diet. Pandas are found in the mountainous regions of China and are classified as vulnerable because of habitat loss and low reproductive rates. Females are only fertile for a few days each year, making reproduction difficult. Conservation efforts have helped increase their population. The giant panda is a symbol of wildlife conservation and through panda diplomacy, it has helped strengthen diplomatic ties between China and other countries. IUCN Status: The IUCN Red List (International Union for Conservation of Nature) currently classifies the giant panda as Vulnerable.

Explanation

The Dugong (Dugong dugon) is a marine mammal found in shallow coastal waters of the Indo-Pacific. It is closely related to manatees. The dugong has a torpedo-shaped body with a fluked tail (similar to a whale’s) and two front flippers. Its skin is grayish-brown, and it has a rounded, wrinkled face that helps it forage for seagrass, its primary food source. Dugongs can grow up to 3 meters in length and weigh up to 400 kg. Dugongs are herbivores and feed mainly on seagrass, earning them the nickname "sea cows". They play a crucial role in maintaining healthy seagrass ecosystems. However, dugongs are vulnerable due to habitat loss, hunting, bycatch, and seagrass degradation. Conservation efforts focus on protecting their habitats through marine protected areas and reducing fishing gear entanglements.

Explanation

The Ministry of Rural Development was designated as the nodal ministry for implementing the National Biodiesel Mission during its initial phases. The mission focused on cultivating Jatropha curcas, a non-edible oilseed crop, on wastelands to produce biodiesel. Jatropha is a plant of Latin American origin, which is now widespread throughout arid and semi-arid tropical regions of the world. This initiative aimed to achieve energy security, promote rural development, and provide an alternative source of livelihood for farmers in marginal and degraded lands.

Explanation

Selene-1 also known as Kaguya is a lunar orbiter mission launched by the Japan Aerospace Exploration Agency (JAXA) using the H-IIA rocket. Its primary objectives were to study the Moon’s origin, evolution, and surface features with unprecedented detail. It mapped the Moon’s mineral composition and gravity anomalies which provided crucial data about its internal structure and geology. As one of the most advanced lunar exploration missions of its time contributing significantly to understanding the Moon’s evolution and mineral distribution.

Explanation

ISRO successfully conducted a rocket test using cryogenic engines at the Liquid Propulsion Systems Centre (LPSC) located in Mahendragiri in Tamil Nadu. ISRO Propulsion Complex (IPRC) is equipped with the state-of-the-art facilities necessary for realising the cutting edge propulsion technology products for the Indian space programme. Formerly, IPRC was known as LPSC, Mahendragiri. The IPRC is responsible for developing cryogenic propulsion systems essential for high-performance launch vehicles. A cryogenic engine uses supercooled liquids, typically liquid oxygen (LOX) and liquid hydrogen (LH2) as propellants. These engines are highly efficient because cryogenic fuels have a higher specific impulse, meaning they provide greater thrust for a given mass of fuel.

Explanation

Options (a), (c) and (d) are incorrect: Apophis was a near-Earth asteroid named after the Egyptian God of chaos. Spitzer is an infrared space telescope launched by NASA in 2003. TechSar is a reconnaissance satellite equipped with synthetic-aperture radar, used for surveillance and intelligence purposes.

Option (b) is correct: Cassini was a groundbreaking planetary exploration mission led by NASA, European Space Agency (ESA), and the Italian space agency (ASI). This advanced robotic spacecraft was designed to study Saturn, its rings, and its moons in extraordinary detail. As part of the mission, Cassini carried the ESA-built Huygens probe, which landed on Saturn’s largest moon, Titan. During its descent through Titan’s dense atmosphere, Huygens captured remarkable images and data, eventually landing on an icy floodplain damp with liquid methane.