General Science Mixed Quiz: Set 55

The correct answer is B, Vitamin C. Vitamin C, or ascorbic acid, is needed to make collagen, the protein that holds tissues together, so its absence weakens the gums and blood vessels and delays the healing of wounds. It was the disease of long sea voyages until citrus fruit was added to rations, and amla, guava and lemon are rich sources. Option A is wrong because a lack of vitamin A causes night blindness and, in severe cases, xerophthalmia. Option C is wrong because a lack of vitamin D causes rickets in children and osteomalacia in adults, since the vitamin is needed to absorb calcium. Option D is wrong because a lack of vitamin K delays the clotting of blood, as it is required to make prothrombin. Vitamin C and the B group are water soluble, while A, D, E and K are fat soluble.

The correct answer is A, 1 and 4. Hooke's law holds only as far as the limit of proportionality, and that limit is either equal to or lower than the elastic limit, so statements 1 and 4 are the correct pair. Hooke's law says stress is proportional to strain, which is the straight part of the stress-strain graph; the point where the curve leaves the straight line is the limit of proportionality. A little beyond it the material still springs back to its original shape, and the last point at which it does so is the elastic limit. For most metals the two points lie very close together and for an ideal material they coincide. B is wrong because statement 2 extends the law past the straight part of the graph, where stress and strain are no longer proportional. C and D are wrong because statement 3 says always less, while the two limits may also be equal. Exam tip: order the four points as proportionality limit, elastic limit, yield point, ultimate stress.

The correct answer is B, oxaloacetic acid, a four-carbon acid, which is exactly why the group is called C4. The gas is first fixed in the mesophyll cells by the enzyme PEP carboxylase on to a three-carbon acceptor, and the pathway is named after Hatch and Slack. Maize, sugarcane, sorghum and amaranthus follow it and show the special leaf anatomy called Kranz anatomy. A is wrong because 3-phosphoglyceric acid is the three-carbon first product of C3 plants such as wheat and rice; the two are swapped in almost every paper that asks this. C is wrong because pyruvic acid is a product of glycolysis in respiration and appears in the C4 cycle only later, when the acid is regenerated. D is wrong because ribulose bisphosphate is the five-carbon acceptor molecule in the Calvin cycle, not a product of fixation at all.

The correct answer is C, fish farming. Pisciculture is the rearing of fish in ponds, tanks and other managed waters, the Latin word piscis meaning fish. It is a branch of aquaculture and India is one of the largest fish producers in the world; the Blue Revolution is the name given to the planned growth of fish output, and rohu, catla and mrigal are the common Indian carps raised in ponds. A is wrong because the rearing of honey bees is apiculture, which gives honey and beeswax. B is wrong because the rearing of silkworms is sericulture, in which the mulberry-fed Bombyx mori gives most of the world's silk. D is wrong because the rearing of birds is aviculture, and the keeping of fowl for eggs and meat is poultry farming. Exam tip: learn the culture words together - pisciculture fish, apiculture bees, sericulture silkworms, aviculture birds, horticulture fruits and vegetables, floriculture flowers.

The correct answer is A, Vitamin A. Vitamin A is used to make rhodopsin, the pigment of the rod cells of the retina that allows sight in dim light, so a shortage of it makes a person unable to see properly at dusk or in a dark room. Prolonged deficiency dries the cornea, a condition called xerophthalmia, which can end in blindness, and carrot, papaya, green leafy vegetables, milk and liver are the usual sources. Option B is wrong because a lack of vitamin B1, thiamine, causes beriberi, with weakness of the nerves and swelling of the legs. Option C is wrong because a lack of vitamin C causes scurvy. Option D is wrong because a shortage of iron causes anaemia, in which the blood cannot carry enough oxygen and the person tires easily. The symptom described in the stem is the key to such questions.

The correct answer is B, Galileo Galilei. Galileo was the first to argue that, with air resistance removed, every body falls with the same acceleration regardless of its mass. He reached this by rolling balls down inclined planes and timing them, and the idea is linked in popular accounts with his experiment from the Leaning Tower of Pisa. This overturned the older belief of Aristotle that heavier bodies fall faster. The acceleration he described is g, about 9.8 metres per second squared near the earth. A is wrong because Einstein built on this in the general theory of relativity through the equivalence principle, long afterwards. C is wrong because Edison was an inventor of the electric lamp and phonograph and did no work on falling bodies. D is wrong because Newton, born the year Galileo died, later explained why this happens through his law of gravitation. Exam tip: remember the order - Galileo found that all bodies fall alike, Newton explained the cause.

The correct answer is B, the anther. A stamen is the male reproductive unit of a flower and has just two parts: a stalk called the filament and a swollen head called the anther, in which pollen grains are produced. All the stamens of a flower together make up the whorl called the androecium. A is wrong because the style is the slender tube of the carpel that connects the stigma to the ovary, so it belongs to the female whorl. C is wrong for the same reason: the stigma is the sticky tip of the carpel that receives pollen, and candidates who remember only that pollen touches the stigma often pick it by mistake. D is wrong because a sepal is a member of the calyx, the outermost green whorl that protects the bud; it has no reproductive role. The pair to fix in memory is filament and anther for the stamen, stigma, style and ovary for the carpel.

The correct answer is C, Cleaning. In electroplating the article to be coated is made the cathode, the plating metal serves as the anode, and both are dipped in an electrolyte containing a salt of that metal. When current flows, the metal ions travel to the cathode and settle on it. The coating can bond only if the surface is chemically clean, so grease, oil, rust and oxide are stripped off first by degreasing and by pickling in acid; any film left behind makes the plating peel, blister or come out patchy. Option A is wrong because buffing only brings up a shine on a surface that is already clean. Option B is wrong because soldering joins two metals with a filler alloy and has nothing to do with preparing a surface for plating. Option D is wrong because polishing smooths the surface mechanically but does not remove the oily and oxide films that spoil adhesion. Exam tip: the order is clean first, then plate, and the article is always the cathode.

The correct answer is B, a worm. Filariasis is caused by the thread-like nematode Wuchereria bancrofti, which is carried by the Culex mosquito. The adult worms live in the lymph vessels and block them, so fluid collects in the legs, arms or other parts and the skin thickens, producing the swelling that gives the disease its common name of elephantiasis. Option A is wrong because protozoan diseases include malaria, kala-azar, amoebic dysentery and sleeping sickness. Option C is wrong because bacterial diseases of this group include plague and tuberculosis. Option D is wrong because fungal infections of the skin are ringworm and athlete's foot, which do not block lymph vessels. Group the worm diseases together for revision: filariasis, ascariasis caused by the roundworm and taeniasis caused by the tapeworm.

The correct answer is C, Thallophyta. Litmus is a purple dye taken from lichens, and in the classification used in school science lichens are placed in Thallophyta, the group of simple plants whose body is an undifferentiated thallus with no true root, stem or leaf. Algae and fungi belong to the same group, and a lichen is in fact a partnership of an alga and a fungus living together. Litmus is a natural indicator: it stays purple in a neutral solution, turns red in acid and blue in base, and is used both as a solution and as litmus paper. Option A is wrong because gymnosperms are well developed plants with naked seeds, such as pine and cycas. Option B is wrong because pteridophytes, the ferns, are the first plants with vascular tissue. Option D is wrong because bryophytes such as moss and Marchantia are called the amphibians of the plant kingdom. Exam tip: litmus is red in acid, blue in base and purple when neutral.

The correct answer is D, angiosperms, the flowering plants. Their pollen tube carries two male gametes into the ovule; one fuses with the egg to form the diploid zygote, which is syngamy, and the other fuses with the two polar nuclei to form the triploid primary endosperm nucleus, which is triple fusion. Two fusions in a single ovule make the event double fertilisation, and it is found nowhere else in the plant kingdom. A is wrong because bryophytes such as mosses have no pollen tube at all and need water for their motile male gametes to swim to the egg. B is wrong because pteridophytes such as ferns also release swimming gametes and bear no seeds. C is wrong because gymnosperms do form pollen tubes and seeds, but only one gamete fuses with the egg and their nutritive tissue is haploid female tissue, not a triploid endosperm.

The correct answer is C. Ultraviolet light is a transverse wave, not a longitudinal one, so this statement is the wrong one. In an electromagnetic wave the electric and magnetic fields vibrate at right angles to each other and to the direction the wave travels, which is the definition of a transverse wave. Longitudinal waves need a material to squeeze and stretch, and sound is the standard example. Option A is correct because ultraviolet light sits in the electromagnetic spectrum between visible light and X-rays. Option B is correct because electromagnetic waves need no medium and cross empty space, which is how the Sun's ultraviolet rays reach the earth. Option D is correct because ultraviolet wavelengths run from about 400 nanometres down to 10 nanometres, shorter than violet light, and this higher energy is what burns skin and is absorbed by the ozone layer. Exam tip: all electromagnetic waves are transverse; only mechanical waves such as sound can be longitudinal.

The correct answer is B, the sandfly. Kala-azar, also called visceral leishmaniasis, is caused by the protozoan Leishmania donovani and is passed on by the bite of the female sandfly, which breeds in cracks of mud walls and damp soil. The disease brings long fever, weight loss, darkening of the skin and enlargement of the spleen and liver, and it occurs mainly in parts of Bihar, Jharkhand, West Bengal and Uttar Pradesh. Option A is wrong because the housefly carries typhoid, cholera and diarrhoea mechanically on its body and does not transmit Leishmania. Option C is wrong because the tsetse fly of Africa carries sleeping sickness, caused by Trypanosoma. Option D is wrong because the rat flea carries plague, caused by Yersinia pestis. Note that both kala-azar and sleeping sickness are protozoan, with different flies.

The correct answer is A, Two dry surfaces. Coulomb friction, also called dry friction, is the resistance that acts when two solid surfaces touch each other with no lubricant between them. Charles-Augustin de Coulomb set out its rules: the friction force is proportional to the normal reaction, it does not depend on the apparent area of contact, and it is very nearly independent of the sliding speed. Dry friction covers both the static friction that must be beaten before motion can start and the kinetic friction that acts once sliding has begun, and the limiting static value is the larger of the two. Option B is wrong because friction between lubricated surfaces is called fluid or film friction and obeys the laws of viscosity instead. Option C is wrong because relative motion describes kinetic friction, which is only one part of Coulomb friction. Option D is wrong because the resistance between a solid and a liquid is viscous drag. Exam tip: Coulomb friction means dry friction, proportional to the normal reaction and independent of the contact area.

The correct answer is B, the ovary. Once fertilisation is complete, the ovary enlarges and ripens into the fruit, and its wall becomes the pericarp that may be fleshy, as in a mango, or dry, as in a pea pod. A is wrong, and is the single commonest error in this question, because each ovule inside the ovary becomes a seed, not the fruit; the number of seeds in a fruit therefore tells you how many ovules the ovary held. C is wrong because the style, like the stigma, usually withers and falls away after pollination, having served only to carry the pollen tube down to the ovule. D is wrong because petals are display organs that attract pollinators and drop off soon after pollination. Note also that a fruit formed from the ovary alone is a true fruit, while apple and pear, whose flesh comes from the thalamus, are false fruits.

The correct answer is A, Crown Gall. Crown gall is caused by the bacterium Agrobacterium tumefaciens, which enters through a wound near the base, or crown, of the stem and makes the plant grow rough tumour-like swellings there. The bacterium works by pushing a piece of its own Ti plasmid into the plant's cells and forcing them to divide, and that natural trick is why laboratories use it as a vector to carry new genes into plants. Grapevine, apple, rose, walnut and stone fruits suffer the most. Option B is wrong because mosaic diseases, such as tobacco mosaic, are caused by viruses that mottle the leaves in light and dark patches. Option C is wrong because smut of wheat, bajra and sugarcane is a fungal disease that fills the ear with black powdery spores. Option D is wrong because white blister, or white rust, of crucifers such as mustard is also fungal and raises white blisters on leaves and stems. Exam tip: bacterial — crown gall, citrus canker, bacterial blight of rice; viral — mosaic, leaf curl; fungal — smut, rust, blight.

The correct answer is C, Rabies. Rabies is caused by a virus present in the saliva of an infected animal, usually a dog, and it travels along the nerves to the brain, where it causes inflammation, fear of water and almost certain death once the symptoms begin; it is prevented by vaccination after the bite, a method that goes back to Louis Pasteur. Option A is wrong because tuberculosis is caused by the bacterium Mycobacterium tuberculosis. Option B is wrong because cholera is caused by the bacterium Vibrio cholerae, which acts through a toxin in the small intestine. Option D is wrong because typhoid is caused by the bacterium Salmonella typhi and is diagnosed by the Widal test. Keep a short list of viral diseases ready: polio, measles, mumps, rabies, dengue, chickenpox, influenza, hepatitis and smallpox.

The correct answer is B, a stem. The potato is an underground stem tuber, and the proof is on its skin: the hollows called eyes are axillary buds with tiny scale leaves, and buds of this kind are never found on a true root. That is why a cut piece of potato with an eye grows into a whole new plant. A is wrong because the familiar modified roots are the sweet potato, carrot, radish, turnip and beetroot, none of which carries buds. C is wrong because modified leaves give us the fleshy scales of an onion bulb, the tendrils of a pea and the spines of a cactus, but not the potato. D is wrong because the potato is not a reproductive structure in the floral sense; the potato plant does bear flowers separately. Group the modified stems for revision: potato tuber, ginger and turmeric rhizomes, onion and garlic bulbs, colocasia corm.

The correct answer is B, Iodine. The thyroid gland needs iodine to make the hormones thyroxine and triiodothyronine, and when the supply is short the gland enlarges in an attempt to trap more of it, which appears as a swelling in the neck. Severe deficiency in children causes cretinism, with stunted growth and reduced mental development, and the remedy adopted in India is the sale of iodised salt. Option A is wrong because a lack of calcium weakens bones and teeth and can cause spasms of the muscles. Option C is wrong because a shortage of iron causes anaemia, since iron is part of haemoglobin. Option D is wrong because a lack of vitamin D causes rickets and osteomalacia, although it indirectly affects calcium. Note that iodine is a mineral, not a vitamin, which papers sometimes test.

The correct answer is C, ethylene, the only plant hormone that is a gas. It hastens the ripening of fruit, encourages leaves and flowers to drop and is used commercially in the form of ethephon to ripen mangoes, bananas and tomatoes evenly; a ripe fruit kept with unripe ones ripens them because it gives off ethylene. A is wrong because auxin is the hormone of cell elongation, bending towards light and apical dominance, and in high doses it works as a weedkiller. B is wrong because gibberellin lengthens stems, breaks seed dormancy and causes bolting in rosette plants; it is associated with growth in height rather than ripening. D is wrong because cytokinin promotes cell division, delays the ageing of leaves and helps shoots form in tissue culture. The hormone to pair with stress is abscisic acid, which closes the stomata and enforces dormancy.