UPSC Prelims 2013 Analysis

Explanation

Root hairs are extremely delicate, whether on a tree or a seedling. When transplanting young trees from a nursery to a woodland, damage to the roots and root hairs often leads to the death of a tree.

Explanation

Fruits and vegetables continue their metabolic activity after harvest.

Metabolic Activity is manifested by respiration .

Reduction of temperature is an effective means of reducing the rate of respiration .

Explanation

A rainbow is always formed in a direction opposite to that of the Sun. The water droplets act like small prisms.

Physical Phenomena Involved here are

Refraction Light bends when it enters and exits water droplets, due to the change in speed when traveling between air and water. Dispersion White sunlight is made up of different colors (wavelengths) of light. When light refracts, these different colors bend at slightly different angles, separating them. Internal reflection Light bounces off the inside of the back of the raindrop.

The correct solution is (d) 1, 2 and 3

Explanation

Among marine creatures, the sea cow and sea lion are mammals, while the sea horse is a fish.

The sea cow, a herbivorous marine mammal, resides in the Indian and Pacific Oceans, growing to 3m and weighing around 600kg. Sadly, it's vulnerable due to habitat degradation and hunting.

The sea lion, a carnivorous marine mammal, breeds on Pacific beaches. It grows to 2.5m, weighs around 350kg, and is Endangered.

The sea horse, a carnivorous marine fish, is found in shallow tropical waters. It grows to 35cm, weighs around 200g, and is vulnerable due to habitat damage and fishing.

Explanation

Mycorrhizal plants have tolerance to adverse soil, PH, high temp., drought, and toxic heavy metals.

The most important role of Mycorrhizal fungi is to absorb nutrients and water from the soil and transfer them to their hosts.

Mycorrhizae help plants withstand root diseases.

Oxalic acid production by mycorrhizal fungi contributes to disease suppression.

Hence, all three statements are correct. Answer (c).

Explanation

Bagasse This fibrous residue left after sugarcane juice extraction is a valuable biomass fuel. It can be burned to generate electricity or heat, often powering the sugar mills themselves.

Molasses While molasses isn't directly used to produce synthetic fertilizers, it can be fermented to create ethanol, a biofuel. Ethanol can be used as a transportation fuel or blended with gasoline.

Synthetic Fertilizers Molasses don't directly contribute to the production of synthetic chemical fertilizers. These fertilizers are typically manufactured using chemical processes involving elements like nitrogen, phosphorus, and potassium.

Thus, statements 1&3 are correct while statement 2 is wrong.

Explanation

Hepatitis B is a liver infection that can lead to liver failure and cancer. It's spread through contact with the blood, open sores, or body fluids of an infected person.

HIV is a virus that destroys the white blood cells responsible for fighting infections. It can result in AIDS, the final stage of infection. It spreads mainly through unprotected sex, sharing drug needles, or contact with infected blood.

Chikungunya is a mosquito-borne viral disease that cannot be spread through tattooing.

Explanation

Since Viruses lack organelles and are totally dependent on the host cell's metabolic machinery for replication, they cannot be grown in synthetic media.

In the laboratory, animal viruses are grown in animals or animal cell culture, and plant viruses are grown in plants or plant plant cell culture.

There are two categories of Vectors biological and mechanical.

• If the virus increases its number while in association with a vector, then that vector is termed as being biological.
• Conversely, the vector is termed to be mechanical, if the virus doesnt increase its number while in association with that vector.

Arthropods such as wasps, which repeatedly can sting multiple animals, could serve as mechanical vectors by transporting viruses on the surface of their stingers.

Explanation

Aflatoxins are poisonous carcinogens that are produced by certain moulds (Aspergillus flavus and Aspergillus parasiticus) which grow in soil , decaying vegetation , hay, and grain .

Explanation

A ball bearing is a type of Rolling element bearing that uses the ball to maintain the separation between the bearing races. The purpose of round ball bearings is to reduce the surface area of contact between the object being moved and the one which is providing the power.

Thus, reduced area means less friction and more efficiency. The balls have a much lower coefficient of friction than the two flat surfaces sliding against each other.

Explanation

Statement 1 is incorrect since gravity is actually the weakest of the four fundamental forces for a given distance.

Electromagnetism acts only on charged particles, where the charge can be negative or positive.

The weak force is responsible for the existence and structure of atomic nuclei including radioactivity and nuclear fusion .

Strong nuclear force is responsible for holding protons and neutrons together inside the atomic nucleus and is 100 times stronger than electromagnetism .

Explanation

Recombinant DNA technology is a major DNA-based tool that opens a new age for modern biotechnology. With this technology, a gene or multiple genes can be identified, cut, and inserted into the genome of another organism.

Golden rice is developed by transferring carrot genes to rice. The new variety of rice contains Vitamin A. Hence, Statement 1 is correct (across different species of plants).

In 1953, scientists discovered the structure of DNA, and in 1972, researchers developed a method for cutting and splicing DNA. That method became known as recombinant DNA, or rDNA. Since then, researchers have learned how to move genetic material in the form of DNA from one plant or animal to another. They can also take DNA from an animal and place it in a plant, and vice versa.

Explanation

All the given minerals have a role in contraction of muscles in the human body.

Calcium Calcium is essential for activating enzymes which cause muscle contraction.

Iron Iron helps support continued muscle function by supporting energy production in your muscle cells so that muscle fibers always have the energy they need to contract properly. Iron also helps muscles store oxygen to fuel muscle contractions and promotes healthy circulation so that muscles can get additional oxygen from the bloodstream.

Sodium One needs sodium for muscle contraction because it balances potassium to maintain membrane potential.

Explanation

Cumulonimbus is an overgrown cumulus cloud, extending from tremendous vertical height from a base of 2000 feet to over 30,000 feet, they are black and white globular masses that take a fantastic range of shapes. They are also referred to as a thunder-cloud and bring convectional rain, accompanied by lightning and thunder. Thunder is the sound caused by a lightning discharge. Lightning heats the air in its path and causes a large over-pressure of the air within its channel. The channel expands supersonically into the surrounding air as a shock wave and creates an acoustic signal that is heard as thunder.

Explanation

Higgs Boson is a particle postulated by the standard model of Physics to provide mass to all particles in the universe. Discovery of the Higgs Boson will help us further understand why elementary particles have mass.

The technology of transferring physical matter without traversing the physical space in between is not presently related to the discovery of Higgs Boson.

Similarly, Higgs Boson will not help in creating better fuels for nuclear fission. It has to be understood that the discovery of Higgs Boson will only confirm what has been already been theorised and is not the discovery of the new principle in Physics.

Explanation

Out of the listed phenomena, 1, 2, and 4 are optical illusions.

Size of the sun at dusk The sun doesn't actually change size throughout the day. The atmosphere acts like a lens, bending the sunlight slightly, making the sun appear larger near the horizon.

Colour of the sun at dawn and dusk The sun doesn't change colour either. Sunlight is made up of various colours with different wavelengths. As sunlight travels through a thicker layer of atmosphere at sunrise and sunset, shorter wavelengths (like blue and violet) scatter more easily, leaving the remaining light to appear redder or orange.

Moon being visible at dawn This one is not an illusion. Depending on the phases of the moon and your location, the moon can indeed be visible at dawn.

The twinkle of stars Stars twinkle due to the Earth's atmosphere. The starlight gets bent as it travels through the different layers of air with varying temperatures and densities. This creates a shimmering effect, making the stars appear to twinkle.

Polarstar being visible in the sky This is not an illusion either. The North Star (Polaris) is nearly aligned with the Earth's axis, making it appear relatively stationary in the night sky compared to other stars that seem to move across the sky due to Earth's rotation. As long as you're in the Northern Hemisphere with a clear view of the northern sky, you should be able to see Polaris.