General Science Questions (MCQs) for Competitive Examinations

Notes:
Magnetite (Fe3O4) typically contains about 70% iron by weight. It is black in color and strongly magnetic. Hematite (Fe2O3) contains about 60–70% iron. Limonite contains 35–50% iron. Siderite (FeCO3) contains about 48% iron. Magnetite is widely mined due to its high iron concentration compared to other ores.

Notes:
Ecological succession is unidirectional progressive process of development in an ecosystem or biome. Grass ecosystems are an early stage of succession in regions where the mature ecosystems are forests. However, grass ecosystems are climax ecosystems in grassland regions, where there is not enough rainfall to support a forest. Due to limiting factors such as water scarcity and forest fire, a grassland ecosystem changes to a desert ecosystem. The ecological succession of grassland is desert.

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Plant wilting occurs after excessive loss of water by transpiration and lesser absorption. i.e. rate of transpiration exceeds rate of water absorption. On a hot day, plants transpire heavily and cannot absorb water speedily to keep pace with transpiration loss, even when there is enough water.

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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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The eustachian tube is a canal that connects the middle ear to the nasopharynx. It controls the pressure within the middle ear, making it equal with the air pressure outside the body. The cochlear nerve is also known as the acoustic nerve. It transfers auditory information from the cochlea (auditory area of the inner ear) to the brain. The malleus transmits the sound vibrations from the eardrum to the incus, and then to the stapes.

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Entomology, branch of anthropology and study of zoology, deals with the scientific study of insects. The Greek word entomon, meaning “notched,” refers to the segmented body plan of the insect. The zoological categories of genetics, taxonomy, morphology, physiology, behaviour, and ecology are included in this field of study.

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A biomass is total quantity of weight of the planet that can be classified according to the plants and animals that live in it. Temperature, soil, and the amount of light and water help determine what life exists in a biome.

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Outer Ear or Pinna is found only in terrestrial mammals. It is composed of a thin plate of yellow elastic cartilage, covered with integument, and connected to the surrounding parts by ligaments and muscles.

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When a DNA solution is heated enough, the double-stranded DNA unwinds, and the Hydrogen bonds that hold the two strands together weaken and finally break. The process of breaking a double-stranded DNA into single strands is known as DNA denaturation, or DNA melting. The hyper-chromicity of DNA occurs when the DNA duplex is denatured.

Notes:
Karl Landsteiner was an Austrian biologist and physician. He is noted for having first distinguished the main blood groups in 1900, having developed the modern system of classification of blood groups from his identification of the presence of agglutinins in the blood, and having identified, with Alexander S. Wiener, the Rhesus factor, in 1937, thus enabling physicians to transfuse blood without endangering the patient’s life.