General Science Questions (MCQs) for Competitive Examinations

Notes:
Stomata are tiny openings or pores in plant tissue that allow for gas exchange. Stomata allow a plant to take in carbon dioxide, which is needed for photosynthesis. They also help to reduce water loss by closing when conditions are hot or dry. Stomata look like tiny mouths which open and close as they assist in transpiration.

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Leukaemia is a type of cancer of the blood or bone marrow characterized by an abnormal increase of immature white blood cells called “blasts”. Damage to the bone marrow, by way of displacing the normal bone marrow cells with higher numbers of immature white blood cells, results in a lack of blood platelets, which are important in the blood clotting process. This means people with leukaemia may easily become bruised, bleed excessively, or develop pinprick bleeds (petechiae). White blood cells, which are involved in fighting pathogens, may be suppressed or dysfunctional. This could cause the patient’s immune system to be unable to fight off a simple infection or to start attacking other normal body cells.

Notes:
Antibiotics are medicines used to treat a wide variety of infections or diseases caused by bacteria, such as respiratory tract infections (eg, pneumonia and whooping cough), urinary tract infections, skin infections and infected wounds. Antibiotics work by blocking vital processes in bacteria, killing the bacteria or stopping them from multiplying.

Notes:
In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure. In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46. The chromosome holds not only the genetic code, but many of the proteins responsible for helping express it.

Notes:
August Wilhelm Eichler, German botanist who developed one of the first widely used natural systems of plant classification. Eichler’s system of plant classification, developed in 1886, eventually won worldwide acceptance. He divided the plant kingdom into four divisions: Thallophyta, Bryophyta, Pteridophyta, and Spermatophyta.

Notes:
The arteries (red) carry oxygen and nutrients away from your heart, to your body’s tissues. The veins (blue) take oxygen-poor blood back to theheart. Arteries begin with the aorta, the large artery leaving the heart. They carry oxygen-rich blood away from the heart to all of the body’s tissues.

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Cellular respiration is a catabolic process because it is breaking down glucose to eventually transfer energy into its usable form in ATP. An anabolic process builds things up, photosynthesis is a version of this and the metabolic opposite of cellular respiration.

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John Dalton was an English physicist who is best known for introducing the atomic theory into chemistry, and for his research into colour blindness. In 1794, he postulated that shortage in colour perception was caused by discoloration of the liquid medium of the eyeball.The thorough and methodical nature of his research into his visual problem was so broadly recognised that Daltonism became a common term for colour blindness.

Notes:
The allotropic form of Phosphorus (white phosphorus) is less stable and therefore highly reactive because of angular strain in P4 molecule where the angles are only 60o. Having very low ignition temperature, it readily catches fire in air to give dense white fumes of P4O10. So it is kept in water to avoid oxidation by the oxygen present in air.

Notes:
Cement (e.g., Portland cement) hardens because of hydration a chemical reaction that occurs independently with the mixture’s water content; they can harden even underwater or when constantly exposed to wet weather. The chemical reaction that results when the anhydrous cement powder is mixed with water produces hydrates that are not water-soluble.