General Science Mixed Quiz: Set 56

The correct answer is B, Haemophilia. Haemophilia is an inherited disorder in which a clotting factor is missing, so bleeding continues for a long time after an injury. The gene lies on the X chromosome, which is why the disease appears mostly in males while females usually carry it, and it is the classic example used to explain sex-linked inheritance along with colour blindness. Option A is wrong because cholera is an infectious disease caused by Vibrio cholerae spreading through water. Option C is wrong because rickets is a deficiency disease that follows a shortage of vitamin D and the poor absorption of calcium. Option D is wrong because trachoma is an infection of the eye caused by Chlamydia trachomatis and is a leading cause of preventable blindness. Other inherited disorders worth listing are sickle cell anaemia, thalassaemia and colour blindness.

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, the garden pea, Pisum sativum. Mendel chose it because it breeds true, is easy to cross by hand, completes a generation in a single season and offers seven pairs of sharply contrasting characters such as tall against dwarf stem and round against wrinkled seed. Option A, maize, became an important material for later geneticists, above all for Barbara McClintock's work on transposable elements, but not for Mendel. Option C, the snapdragon or Antirrhinum, is the plant usually used to illustrate incomplete dominance, where a red and a white parent give pink offspring, so it appears in the same chapter but in a different place. Option D, the evening primrose or Oenothera, was the plant on which Hugo de Vries based his mutation theory. Keep the four pairings separate, because a question often supplies all of them as options.

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 D, J. J. Thomson. In 1897 Thomson passed an electric discharge through a gas at very low pressure and showed that the cathode rays produced were a stream of identical negatively charged particles, far lighter than any atom and the same whatever gas or electrode was used. He called them corpuscles; they were later named electrons, and he measured their charge to mass ratio. Option A, Chadwick, discovered the neutron in 1932 and not the electron. Option B, Niels Bohr, did not discover any particle; he proposed the model in which electrons revolve in fixed energy shells and explained the hydrogen spectrum. Option C, Rutherford, used the scattering of alpha particles by gold foil to establish the small, dense, positively charged nucleus and gave the proton its name. The order to memorise is electron by Thomson in 1897, nucleus and proton by Rutherford, and neutron by Chadwick in 1932.

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 A, Ranikhet. Newcastle disease is called Ranikhet disease in India because the first serious outbreak in the country was reported from Ranikhet in the Kumaon hills, while the name Newcastle comes from Newcastle upon Tyne in England, where it was identified in 1926. It is caused by a paramyxovirus, spreads fast through a flock by droppings and droplets, and shows itself as gasping, greenish diarrhoea, twisted neck and a sharp fall in egg laying, so losses can be heavy. There is no cure, and poultry keepers rely on vaccination with the F and R2B strains along with strict hygiene. B is wrong because IBD, infectious bursal disease or Gumboro, attacks the bursa and the young bird's immunity. C is wrong because coccidiosis is caused by Eimeria, a protozoan, and brings bloody droppings. D is wrong because fowl pox is a different viral disease, marked by warty scabs on the comb and wattles. Exam tip: Ranikhet equals Newcastle disease, a viral disease met by vaccination.

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, 3 : 1. When two heterozygous plants of the first generation are crossed, three quarters of the offspring show the dominant character and one quarter the recessive one, because the recessive appears only when both factors in the pair are recessive. Option A, 1 : 2 : 1, is the genotypic ratio of the same cross, counting one homozygous dominant, two heterozygous and one homozygous recessive, and it is the commonest wrong answer because the question is often read carelessly. Option C, 9 : 3 : 3 : 1, is the phenotypic ratio of a dihybrid cross, where two pairs of characters are followed at once. Option D, 1 : 1, is the ratio obtained in a test cross, where a plant showing the dominant character is crossed with a homozygous recessive to find out whether it is pure or hybrid.

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 C, James Chadwick. In 1932 Chadwick bombarded beryllium with alpha particles and showed that the highly penetrating radiation given off consisted of neutral particles with almost the same mass as a proton. The neutron explained why the mass of an atom is greater than the mass of its protons, and it explained isotopes, so Chadwick received the Nobel Prize in Physics for it. Option A, Marie Curie, worked on radioactivity with her husband Pierre and isolated polonium and radium; she did not discover a nuclear particle. Option B, Rutherford, discovered the nucleus through the gold foil experiment and predicted that a neutral particle must exist, but it was his student Chadwick who found it. Option D, Max Planck, founded the quantum theory by proposing that energy is radiated in packets called quanta. The three-line summary is Thomson for the electron, Rutherford for the nucleus and Chadwick for the neutron.

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 C, the law of independent assortment. In a dihybrid cross two pairs of characters are followed together, for example seed shape and seed colour, and the appearance of all four combinations in the proportion nine to three to three to one shows that the inheritance of one pair does not depend on the inheritance of the other. Option A, the law of dominance, is shown by the first generation, where only one of a pair of contrasting characters appears. Option B, the law of segregation or purity of gametes, is shown by the reappearance of the recessive character in the second generation of a monohybrid cross, which proves that the two factors separated cleanly at gamete formation. Option D is not Mendel's at all; use and disuse belongs to Lamarck's theory of evolution and is placed here as a distractor.

The correct answer is C, 2 s. A simple pendulum about one metre long completes one full swing in roughly two seconds, and a pendulum of this length is called the seconds pendulum. The time period of a simple pendulum is T = 2 pi times the square root of L divided by g, where L is the length of the thread and g is the acceleration due to gravity, about 9.8 metres per second squared. Putting L = 1 metre gives T = 2 x 3.14 x the square root of 1 divided by 9.8, which comes to about 2.01 seconds. The period depends only on the length and on g, not on the mass of the bob or on how far it is pulled aside, so long as the swing is small. A is wrong because a 6 second period needs a thread about 9 metres long. B is wrong because a 4 second period needs a thread about 4 metres long. D is wrong because a 1 second period belongs to a thread of only about 25 centimetres. Exam tip: the period doubles only when the length becomes four times.

The correct answer is C, Faraday and Henry. Working independently in the 1830s, Michael Faraday in England and Joseph Henry in the United States showed that a changing magnetic flux through a circuit sets up an electromotive force in it, and that the effect depends on the rate of change of flux rather than on the flux itself. This single result is the basis of the dynamo, the alternating current generator, the transformer and the induction motor, and the unit of inductance, the henry, is named after Henry. Option A, Rutherford, belongs to nuclear physics and not to electromagnetism. Option B, Einstein, is remembered for the photoelectric effect, for relativity and for the mass energy relation. Option D pairs Planck, the founder of quantum theory, with Fermi, who built the first nuclear reactor, neither of whom worked on induction. Remember that Faraday also gave the laws of electrolysis, so his name appears in chemistry questions too.

The correct answer is A, 250 cm. In an astronomical telescope set for normal adjustment, the magnifying power equals the focal length of the objective divided by the focal length of the eyepiece. Here the magnification is 100 and the eyepiece is 2.5 cm, so the objective must be 100 multiplied by 2.5, that is 250 cm. This is why astronomical telescopes are long instruments: a large objective focal length with a short eyepiece focal length gives high magnification, and in normal adjustment the tube length is roughly the sum of the two focal lengths. B is wrong because an objective of 40 cm would give a magnification of only 16. C is wrong because a focal length smaller than the eyepiece would shrink the image instead of enlarging it. D is wrong because 100 cm gives a magnification of 40. Exam tip: for a telescope magnification is objective divided by eyepiece, so the objective is the longer lens.

The correct answer is B, Wilhelm Johannsen, the Danish botanist who gave the words gene, genotype and phenotype, distinguishing the hereditary constitution of an organism from its visible expression. Option A, William Bateson, coined the word genetics itself for the new science of inheritance and championed Mendel's rediscovered work in the English-speaking world, so he is the obvious confusion here. Option C, Walter Sutton, with Theodor Boveri put forward the chromosome theory of inheritance in 1902, which located Mendel's factors on the chromosomes. Option D, Thomas Hunt Morgan, worked on the fruit fly Drosophila and established linkage and the mapping of genes along a chromosome, winning the Nobel Prize for it. The set to memorise is Bateson for genetics, Johannsen for gene, Sutton and Boveri for chromosomes and Morgan for linkage.

The correct answer is B, amber. Elektron is the Greek name for amber, the fossilised tree resin which the ancient Greeks found would attract straw, feathers and bits of dust after being rubbed with fur. Because amber was the first material in which this attraction was noticed, the whole science that grew out of it was named electricity, and the particle Thomson discovered in 1897 was named the electron. Option A, ebonite, is a hard vulcanised rubber used in school experiments on static electricity; it is a modern material and not the source of the word. Option C, charge, is the physical quantity that the phenomenon involves, but it is not what the Greek word means. Option D, negative, describes the sign of the charge an electron carries, which was fixed by convention long after the Greek word was coined. Questions on the origin of scientific words are set often, so remember amber for elektron and atomos, meaning indivisible, for atom.

The correct answer is A, Watson and Crick. James Watson and Francis Crick published the double helix model in 1953, with two strands running in opposite directions and bases paired on the inside, using the X-ray diffraction photographs produced by Rosalind Franklin and Maurice Wilkins; Watson, Crick and Wilkins shared the Nobel Prize in 1962. Option B, Hershey and Chase, showed in 1952 by labelling a bacteriophage that DNA and not protein is the material that enters a bacterium and directs it. Option C, Avery and MacLeod, with Colin MacCarty, identified DNA as the transforming principle in the 1940s, building on Griffith's experiment of 1928. Option D, Miller and Urey, performed the experiment of 1953 in which amino acids formed from a mixture of gases and an electric discharge, which belongs to the origin of life and not to the structure of DNA.

The correct answer is B, barometer. A barometer measures the pressure of the atmosphere, and the mercury barometer invented by Evangelista Torricelli in 1643 does so by balancing the weight of the air against a column of mercury about 76 centimetres high at sea level. A sudden fall in the reading means that a storm is approaching, while a steady high reading means fine weather, so the instrument is the foundation of weather forecasting. Option A, hygrometer, measures the humidity or the amount of water vapour in the air. Option C, anemometer, measures the speed of the wind, usually with three or four cups that spin on a vertical axis. Option D, lactometer, measures the relative density of milk and so indicates whether it has been diluted. The trap to watch for is manometer, which also measures pressure but the pressure of an enclosed gas rather than that of the open atmosphere.