General Science Previous Year Questions (PYQ) with Answers – Page 71

A whale is a mammal, not a fish, so it breathes with lungs and must come to the surface to take air through a blowhole on top of its head.

Geitonogamy is pollination between two different flowers borne on the same plant.

The buccal cavity is the mouth, and the saliva poured into it begins the digestion of starch, a carbohydrate. Three pairs of salivary glands supply saliva, which carries the enzyme salivary amylase, also called ptyalin.

Ashwagandha, whose botanical name is Withania somnifera, is called winter cherry in English because of the small red berry it bears inside a papery cover; it is also called Indian ginseng.

The loudness or intensity level of sound is measured in decibels (dB), a unit named after Alexander Graham Bell.

Liquefied petroleum gas is a mixture of these two saturated hydrocarbons, which are gases at ordinary pressure but turn liquid under moderate pressure, so a large quantity of fuel fits into a small cylinder; a strong-smelling compound is added so that a leak is noticed.

Silver is an element, a pure metal with its own place in the periodic table, so it cannot be an alloy; an alloy is a homogeneous mixture of two or more metals, or of a metal with a non-metal such as carbon.

The left atrium is the chamber that receives oxygen-rich blood coming back from the lungs through the pulmonary veins. From there the blood passes the bicuspid or mitral valve into the left ventricle, which pumps it out through the aorta to the whole body.

Dendrites and the axon are the two kinds of processes that grow out of a neuron, the nerve cell that carries messages through the body.

The small intestine is the longest part of the human alimentary canal, about 6 to 7 metres in an adult, which is why it is called the longest organ of the digestive system.

Water behaves unlike most liquids between 0 and 4 degrees Celsius, a behaviour called the anomalous expansion of water. Almost every substance shrinks as it is cooled, but water shrinks only until it reaches 4 degrees Celsius.

Arteries are the blood vessels that carry blood away from the heart to the different parts of the body. Because the heart pushes blood into them under high pressure, arteries have thick, muscular and elastic walls and no valves, and they are placed deep in the body.

Bos mutus is the scientific name of the wild yak, the long haired bovine of the high cold plateaus of Ladakh, Tibet and the Karakoram, which grazes above four thousand metres and is listed as Vulnerable on the IUCN Red List.

A tunnel diode, also called an Esaki diode after Leo Esaki who made it in 1957, is heavily doped on both sides, so its depletion layer is extremely thin and electrons cross it by quantum tunnelling.

Newton's universal law of gravitation states that every two bodies attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them, written F = GMm/d².

Aerobic respiration is the breakdown of glucose in the presence of oxygen, giving carbon dioxide, water and a large amount of energy.

Potassium sits in group 1 of the periodic table along with lithium, sodium, rubidium, caesium and francium, and these six are called the alkali metals because their oxides and hydroxides dissolve in water to give strong alkalis.

Graphite is built of flat sheets of carbon atoms arranged in hexagons, and while the atoms inside a sheet are joined by strong covalent bonds, the sheets themselves are held to one another only by weak van der Waals forces.

Bacteria are grouped by shape, and bacilli are the rod-shaped ones; the Latin word bacillus itself means a small rod or stick.

Thrust is the force acting perpendicular to a surface, and the thrust acting on unit area of that surface is called pressure, so pressure = thrust ÷ area.