General Science Questions (MCQs) for Competitive Examinations

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Radon, a radioactive noble gas with atomic number 86, is used in radiotherapy. Created by disintegration of radium, its one of the heaviest gases and a health hazard. Radon gas, chemically inert yet radioactive, can accumulate in buildings and drinking water causing lung cancer. Furthermore, radon is noted for brilliant phosphorescence when cooled below its freezing point. Its most stable isotope, 222Rn, has a half-life of 3.8 days. Groundwater often has a higher 222Rn concentration than surface water due to less exposure to atmosphere.

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Keratin is a family of fibrous structural proteins involved in making up the outer layer of human skin. It is also the key structural component of hair and nails. Cells in the epidermis contain a structural matrix of keratin, which makes this outermost layer of the skin almost waterproof, and along with collagen and elastin, gives skin its strength. It also makes up fish scales and crustacean shells, bird feathers and beaks, animal horns and hooves.

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The brain’s limbic system controls emotional expression through the hypothalamus, which has control over the body’s emotional responses systems. The hypothalamus is responsible for regulating hunger, thirst, response to pain, levels of pleasure, sexual satisfaction, anger and aggressive behavior, etc. It also regulates pulse, blood pressure, breathing, and arousal in response to emotional circumstances.

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According to 11th Fiver Year Plan, the Second Green Revolution aims to meet the problems of small and marginal farmers for providing income security to a large section of rural households and treating them as partners of development instead of a mere beneficiary of some government schemes or programme.

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Nitrogen-fixing bacteria are microorganisms capable of transforming atmospheric nitrogen into fixed nitrogen. Rhizobium is one such bacteria that is associated with leguminous plants (e.g., various members of the pea family). It invades the root hairs of host plants and convert free nitrogen to ammonia, which the host plant utilizes for its development.

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Fluorine is the element that is associated with teeth disorder because the presence of sodium fluoride in drinking water at the level of 2ppm may cause mottled enamel in teeth, skeletal fluorosis, and may be associated with cancer and other diseases. However, topically applied fluoride (toothpaste, dental rinses) has been shown to help reduce dental caries.

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Both polio and chicken pox are caused by virus. Poliomyelitis, often called polio or infantile paralysis, is an infectious disease caused by the poliovirus; while, Chickenpox, also known as varicella, is a highly contagious disease caused by the initial infection with varicella zoster virus (VZV).

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Vermicomposting is the process of using worms also called red worms and micro-organisms to turn kitchen waste into black, earthy-smelling, nutrient-rich humus. Vermicompost is an excellent, nutrient-rich organic fertilizer and soil conditioner.

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Photosynthesis is the process by which light energy is converted into chemical energy by organisms. Carbon dioxide and water are the raw materials of this process. The light energy comes from the Sun and its end products are oxygen and glucose.

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New born babies and children normally breathe faster than older children and adults. Their respiratory rate is about 30-60 breaths per minute. The respiratory rate for the different age-categories of children is:-6-12 months: 24-30; 1-5 years: 20-30; 6-12 years: 12-20.