Science and Technology: UPSC Previous Year Questions (Prelims)

Explanation

Option (c) is correct: Eye donation typically involves the donation of the cornea, the transparent, dome-shaped layer at the front of the eye. The cornea is crucial for focusing light on the retina and plays a key role in vision. Corneal transplants are performed to restore vision in people suffering from corneal blindness or damage, which can result from conditions like injury, infections, or diseases.

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

The iris controls the amount of light entering the eye by adjusting the size of the pupil. While important for vision, the iris is not typically used in eye donation. The retina is the light-sensitive layer at the back of the eye responsible for sending visual information to the brain. Retinal transplants are highly complex and not commonly done in eye donation. The lens focuses light on the retina but is not commonly donated for transplant.

Explanation

A is matched with 1: Adrenaline, produced by adrenal gland is associated with the body’s response to stress, especially during situations of anger, fear, or danger. It triggers the "fight or flight" response, increasing heart rate, blood pressure, and energy supply. B is matched with 3: Estrogen is indeed the primary female sex hormone that regulates the development of female reproductive tissues and secondary sexual characteristics such as breast development and menstruation. C is matched with 4: Insulin is a hormone that regulates blood glucose levels, facilitating the uptake of glucose by cells for energy. D is matched with 2: Pheromones are chemicals released by animals or humans that influence the behavior of others, particularly related to attracting partners through the sense of smell.

Explanation

A is matched with 3: Atropine is an alkaloid used primarily to dilate the pupil during eye exams or surgeries. It is also used in emergency situations to treat heart trouble, especially in cases of bradycardia (slow heart rate). B is matched with 1: Ether is an anesthetic and was historically used for local anesthesia or as a general anesthetic in surgeries. C is matched with 2: Nitroglycerine is used to treat heart trouble, especially angina (chest pain) by dilating blood vessels and reducing the heart’s workload. D is matched with 4: Pyrethrin is a natural insecticide, derived from chrysanthemums, used for mosquito control and to manage other pests like lice.

Explanation

Royal haemophilia (also known simply as haemophilia) is a sex-linked recessive genetic disorder. It is an X-linked recessive genetic disorder characterized by impaired blood clotting due to deficiencies in clotting factors, primarily Factor VIII (Haemophilia A) or Factor IX (Haemophilia B). It primarily affects males, as the gene responsible for haemophilia is located on the X chromosome. Females can be carriers. Queen Victoria of England was a carrier of haemophilia B and passed the trait to several of her children, including her son Leopold, who died from a hemorrhage after a fall when he was 30.

Explanation

Lathyrism is a neurological disorder caused by the excessive consumption of khesari dal (also known as Lathyrus sativus), a type of legume commonly grown in India and some other regions. The condition is linked to the presence of toxic compounds in the dal, specifically -ODAP (-oxalylamino-L-alanine), which can cause damage to the nervous system, leading to symptoms like paralysis, muscle weakness, and spasticity.

Explanation

A fuse is a safety device designed to protect electrical circuits from overloads or short circuits. It works by having a thin wire or filament that melts when the current exceeds a certain level, breaking the circuit and preventing damage to electrical appliances. The fuse is specifically made with a low melting point to ensure it melts quickly in the event of excessive current flow, protecting the circuit from potential damage. Options (a), (b) and (d) are incorrect:

They are wired in series with the circuit not parallelbecause this setup ensures that the full current passing through the circuit flows through the fuse. This allows the fuse to effectively interrupt the circuit and halt the electrical flow in the event of an overcurrent. Fuses are not constructed from silver alloys as they are usually made from materials such as copper, zinc, or tin. They do not need high resistance rather, they should allow normal current flow until the current exceeds a safe limit. Direction: The following item consists of two statements, one labeled as the Assertion (A) and the other as Reason (R). You have to answer this item using the code given below.

Explanation

Assertion (A) is true: The flow of electric current through a conductor causes energy dissipation in the form of heat due to the collisions between free electrons and the metal atoms. Reason (R) is true: As electrons travel through a metal as they collide with metal atoms causing the atoms to vibrate more and collide with each other which produces heat. The phenomenon is known as Joule heating. When current flows through the metal wire, the free electrons that carry the current interact with the metal atoms, transferring energy and causing the atoms to vibrate more, leading to a temperature increase due to Joule heating. The amount of heat generated depends on factors such as the wire’s resistance, the current, and the duration of the current flow. This effect is the foundation for devices like electric heaters. Thus Reason (R) explains Assertion (A)

Explanation

A is matched with 2: Dr. Raja Ramanna was a distinguished Indian physicist best known for his role in the development of India’s nuclear program, including the Pokhran-I nuclear test in 1974. B is matched with 5: Dr. Swaminathan is renowned for his contributions to the Green Revolution in India, which transformed the country into a self-sufficient food producer. His focus on developing high-yield and disease-resistant crop varieties, combined with sustainable agricultural practices, earned him global recognition in agricultural science. C is matched with 4: Prof. Udupi Ramachandra Rao was a visionary space scientist who led the design and launch of India’s first satellite, Aryabhata, in 1975. Also as the chairman of ISRO, he contributed significantly to advancing India’s space program. D is matched with 3: Prof. Meghnad Saha is celebrated for the Saha Ionization Equation, which explains the physical and chemical conditions in stars. He also made notable contributions to thermodynamics.

Explanation

Zirconium is an essential element for the construction of nuclear reactors due to its unique properties:

Low Neutron Absorption: Zirconium has a low neutron absorption cross-section, making it ideal for use in nuclear reactors as it does not interfere significantly with the nuclear chain reaction. High Corrosion Resistance: It is resistant to corrosion in the presence of coolant water, including high-temperature water, which is commonly used in nuclear reactors. Strength and Durability: Zirconium alloys are strong and durable, making them suitable for structural components like cladding for fuel rods. This combination of properties makes zirconium critical in the nuclear industry.

Explanation

A is matched with 4: Blue vitriol is the common name for copper sulphate, known for its bright blue color. B is matched with 3: Epsom salt is the common name for magnesium sulphate, often used in bath salts and as a laxative. C is matched with 1: Baking soda is sodium bicarbonate, used in cooking as a leavening agent. D is matched with 2: Caustic soda is the common name for sodium hydroxide (NaOH), a strong base used in industrial applications like soap making.