RRB ALP 2024 Previous Year GK Questions with Answers

The correct answer is B, Producers. Producers, the green plants and algae, are the most numerous living part of an ecosystem because every other organism depends on them for food. They make their own food by photosynthesis using sunlight, so they form the first trophic level of every food chain. Only about 10 per cent of the energy passes from one level to the next (Lindeman's ten per cent law), so each higher level can support fewer organisms. This gives the upright pyramid of numbers in a grassland: many grass plants, fewer grasshoppers, fewer frogs, and very few snakes and hawks. A is wrong because primary consumers, the herbivores, feed on producers and are fewer than them. C is wrong because secondary consumers, the small carnivores, are fewer still. D is wrong because tertiary consumers, the top carnivores such as the tiger or eagle, are the fewest of all. Exam tip: Producer → primary consumer → secondary consumer → tertiary consumer; about 90 per cent of energy is lost at each step; in a single-tree ecosystem the pyramid of numbers is inverted.

The correct answer is D, Heating effect. An iron, toaster, oven, kettle and heater all turn electrical energy into heat when current flows through a coil of high resistance. This is explained by Joule's law of heating: heat produced H = I²Rt, so the heat grows with the square of the current, with the resistance and with the time. The heating coils are made of nichrome, an alloy of nickel and chromium, because it has high resistance and does not melt or oxidise easily when red hot. The electric fuse and the filament bulb also work on this effect. A is wrong because the chemical effect of current is used in electroplating and in charging batteries. B is wrong because the magnetic effect runs electric bells, fans, motors and electromagnets. C is wrong because the physiological effect is the shock or muscle twitch that current causes in a living body. Exam tip: H = I²Rt; heater coil = nichrome, bulb filament = tungsten, fuse wire = tin-lead alloy with a low melting point.

The correct answer is C, a concave lens of suitable power. A concave lens spreads the light rays slightly before they enter the eye, so the image moves back onto the retina. In myopia, or short-sightedness, a person sees nearby objects clearly but distant objects look blurred. It happens when the eyeball is too long or the eye lens is too curved, so light from far objects meets in front of the retina. Concave lenses have negative power, so spectacles for myopia carry a minus number such as -2.0 D (dioptre). A is wrong because a biconvex lens brings rays together and would make the blur worse. B is wrong because a plain glass plate has no power and does not change where the rays meet. D is wrong because a convex lens corrects hypermetropia, or long-sightedness, in which the image forms behind the retina. Exam tip: Myopia = concave (minus) lens; Hypermetropia = convex (plus) lens; Presbyopia in old age = bifocal lens; Astigmatism = cylindrical lens.

The correct answer is B, Adrenal gland. Adrenaline is made by the adrenal glands, which sit like caps on top of the two kidneys. It is released in fear, anger or sudden danger, so it is called the "fight or flight" hormone. It raises the heartbeat and breathing rate, increases blood sugar and sends more blood to the muscles so that the body can react fast. Adrenaline comes from the inner part of the gland, the adrenal medulla; the outer part, the cortex, makes cortisol and aldosterone. A is wrong because the thyroid gland in the neck makes thyroxine, which controls metabolism and needs iodine. C is wrong because the pineal gland in the brain makes melatonin, which controls the sleep-wake cycle. D is wrong because the pituitary gland makes growth hormone and controls several other glands, so it is called the master gland. Exam tip: Adrenal = adrenaline (emergency hormone), Thyroid = thyroxine (metabolism), Pancreas = insulin (blood sugar), Pituitary = master gland.