General Science Questions (MCQs) for Competitive Examinations

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Plasma is considered a distinct “fourth state of matter. A plasma is a hot ionized gas consisting of approximately equal numbers of positively charged ions and negatively charged electrons. The characteristics of plasmas are significantly different from those of ordinary neutral gases.

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Steel is an alloy made by combining iron and other elements, the most common of these being carbon. When carbon is used, its content in the steel is between 0.2% and 2. 1% by weight, depending on the grade. Other alloying elements sometimes used are manganese, chromium, vanadium and tungsten. Carbon and other elements act as a hardening agent, preventing dislocations in the iron atom crystal lattice from sliding past one another.

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Edible seaweed products have been consumed in many Asian countries. Edible seaweeds accumulate iodine from seawater and are therefore a good dietary source of iodine. Adequate consumption of seaweed can eliminate iodine deficiency disorders, but excessive iodine intake is not good for health. The recommended dietary reference intake of 0.15 mg/d and 0.14 mg/d for iodine has been established in the United States and Taiwan, respectively. Seaweed is an excellent source of iodine. However, the amount it contains depends on the species. Kombu kelp offers the highest amount of iodine, with some varieties containing nearly 2,000% of the daily value in one gram. Seaweed is a source of iodine, necessary for thyroid function and to prevent goitre. However, an excess of iodine is suspected in the heightened cancer risk in Japanese who consume a lot of the plant, and even bigger risks in post-menopausal women.

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Biofortification is the breeding crops to increase their nutritional value. This can be done either through conventional selective breeding or genetic engineering. Biofortification differs from ordinary fortification because it focuses on making plant foods more nutritious as the plants are growing, rather than having nutrients added to the foods when they are being processed.

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Intensive farming is an agricultural intensification and mechanization system that aims to maximize yields from available land through various means, such as heavy use of pesticides and chemical fertilizers. It is characterized by a low fallow ratio, higher use of inputs such as capital and labour, and higher crop yields per unit land area.

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Saprophytes are the organisms which depend for food on dead and decaying material. They secrete digestive substances into the surrounding environment and break down the organic matter into simpler substances. The nutrients thus produced are absorbed directly through the cell membranes of the organisms.

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Veins carry the deoxygenated blood from different parts of the body to the heart. There are two main veins that carry out this job. The superior vena cava carries deoxygenated blood from head, neck, thorax and hands to the right atrium of our heart. The inferior vena cava carries deoxygenated blood from legs, pelvic region and abdominal organs to the right atrium of our heart. Among the veins, only pulmonary vein carries oxygenated blood.

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The small intestine, the part of the gastrointestinal tract between the stomach and the large intestine, is the main digester and absorber of food. The small intestine has three distinct regions – the duodenum, jejunum, and ileum–that carry out the absorption of nutrients and minerals from food. It converts the food into a semi-solid mass.

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Mycobacterium leprae is a bacillus (rod-shaped) bacterium that causes leprosy, also known as “Hansen’s disease”, which is a chronic infectious disease that damages the peripheral nerves and targets the skin, eyes, and muscles, upper respiratory tract, and nasal mucosa (lining of the nose).

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Silk worms are the larva of a moth (Bombyx mori) native to Asia that spins a cocoon of fine, strong, lustrous fiber that is the source of commercial silk. Silkworms feed on the leaves of the mulberries (genus- Morus) and sometimes on the Osage orange (Maclura pomifera).