General Science Questions (MCQs) for Competitive Examinations

Notes:
Mercury belongs to the zinc group of elements in the periodic table, which comprises zinc, cadmium and mercury. They all have completely filled-up atomic orbitals. It becomes difficult to knock out these electron(s) from their orbitals and form metallic bonds. With its filled shell electron configuration it is very reluctant to form bonds even with other mercury atoms.

Notes:
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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Typhoid is a common worldwide bacterial disease transmitted by the ingestion of food or water contaminated with the feces of an infected person, which contain the bacterium Salmonella enterica subsp. enterica, serovar Typhi.

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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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Mitochondria is an organelle found in large numbers in most cells, in which the biochemical processes of respiration and energy production occur. It is for this reason that mitochondria are often referred to as the powerhouses of the cell mitochondria also play a key role in the ageing process as well as in the onset of degenerative disease.

Notes:
A virus has a simple structure. It has no internal cellular structure, no cell wall or cell membrane, just the protein coat that holds the string of nucleic acid. It is made only of a nucleic acid + a protein coat. A cell wall is a layer located outside the cell membrane found in plants, fungi, bacteria, algae, and archaea.

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Cnidarian, also called coelenterate, any member of the phylum Cnidaria (Coelenterata), a group made up of more than 9,000 living species. ? Mostly marine animals, the cnidarians include the corals, hydras, jellyfish, Portuguese men-of-war, sea anemones, sea pens, sea whips, and sea fans.

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The Gambusia fish, also known as larvivorous stagnant water fish. It feeds on the larvae of mosquitoes. So it helps in controlling their population. It is also called ‘mosquito fish’ and is being used as a biological control measure. Hence, a check on malaria and other vector borne diseases like even dengue.

Notes:
Bacteriophage refers to any of a group of viruses that infect bacteria. Bacteriophages were discovered independently by Frederick W. Twort in Great Britain (1915) and Felix d’Herelle in France (1917). D’Herelle coined the term Bacteriophage, meaning “bacteria eater”.

Notes:
The best way of getting rid of non-biodegradable waste such as plastic is by recycling them. Recycling is the process of converting waste materials into new materials and objects. The recovery of energy from waste materials is often included in this concept. Recycling is a key component of modern waste reduction and is the third component of the “Reduce, Reuse, and Recycle” waste hierarchy. Burning may release toxic gas into the atmosphere. Burying and dumping will hardly solve anything because of their very long life of self decomposition.