General Science Questions (MCQs) for Competitive Examinations

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Common table salt plays a primary role in the processes of digestion and absorption. Salt activates an enzyme in the mouth called salivary amylase. Salt also creates hydrochloric acid. Hydrochloric acid is a very important digestive secretion, which lines the stomach walls.

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Oxygen liberated during photosynthesis comes from the splitting or hydrolysis of water in the green plants. Cornelius van Niel experimentally proved for the first time that the oxygen liberated during photosynthesis comes from water and not from carbon dioxide. Oxygen is expelled out of plants and Hydrogen is used to reduce Carbon dioxide to produce carbohydrates.

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The organs which have different basic structure and origin abut are similar in their appearance and functioning, are called analogous organs. An example of analogous organs are the wings of insects, bats and birds that evolved independently in each lineage separately after diverging from an ancestor without wings.

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Potatoes are examples of tubers : the swollen ends of stolons that may store starch. It is a stem because it has many nodes called eyes with spaces between eyes known as internodes. Potato tubers develop at the end of swollen underground stem structures, rhizomes.

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Marsupial, any of more than 250 species belonging to the infraclass Metatheria, a mammalian group characterized by premature birth and continued development of the newborn while attached to the nipples on the mother’s lower belly. The pouch—or marsupium, from which the group takes its name—is a flap of skin covering the nipples. Well-known marsupials include kangaroos, wallabies, koalas, possums, etc.

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Tuberculosis (TB) is an infectious disease of the lungs. It is typically caused by bacteria called Mycobacterium tuberculosis. The common cold is a viral infectious disease of the upper respiratory tract that primarily affects the nose. AIDS (acquired immunodeficiency syndrome) is a syndrome caused by a virus called HIV (human immunodeficiency virus). Dengue fever is a mosquito-borne tropical disease caused by the dengue virus.

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Those who eat a well-balanced diet and have no metabolic disorders, excess dietary carbohydrates?are converted by the liver into complex chains of glucose called glycogen. Glycogen is stored in liver and muscle cells and is a secondary source of energy to freely circulating blood glucose.

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Palisade parenchyma is the layer of tissue directly beneath the epidermis of the upper surface of a leaf. It contains the cylinder-shaped cells that hold the chloroplasts and constitutes the primary area of photosynthesis that converts the light energy to the chemical potential energy of carbohydrates.

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The femur (pl. femurs or femora), or thigh bone, is the most proximal (closest to the center of the body) bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in the rear legs. By most measures the femur is not only the largest but also other of the strongest bones in the body head of the femur articulates with the acetabulum.

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Birds excrete their nitrogenous wastes as uric acid in the form of a paste. This involves a complex metabolic pathway that is energetically costly in comparison to processing of other nitrogenous wastes such as urea or ammonia, but has the advantages of reducing water loss and preventing dehydration. Uric acid is also excreted by terrestrial reptiles (snakes and lizards).