General Science Questions (MCQs) for Competitive Examinations

Notes:
Time required for the organism to eliminate 50 per cent of the total body burden or tissue concentration of chemical is referred to as Half Life Period. A biological half-life or elimination half-life is the time it takes for a substance (drug, radioactive nuclide, or other) to lose one-half of its pharmacologic, physiologic, or radiological activity.

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In citrus fruits such as oranges, the nucleus cells that surround the embryo start dividing and protrude into the embryo sac. These develop into embryos; thus resulting in the presence of more than one embryo inside each ovule. This condition is known as polyembryony.

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Fertilization is the process of fusion of the male and the female gametes. This can occur either inside (internal fertilization) or outside (external fertilization) the body of the female. Humans provide an example of the former whereas seahorse reproduction is an example of the latter.

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Mostly medicinal herbs grown from 30 to 90 cm in height. They reach up to 30 cm in diameter.

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‘Survival of the fittest’ is a phrase that originated from Darwinian evolutionary theory as a way of describing the mechanism of natural selection. Herbert Spencer first used the phrase, after reading Charles Darwin’s On the Origin of Species, in his Principles of Biology (1864), in which he drew parallels between his own economic theories and Dar-win’s biological ones.

Notes:
Chlorophyll, a photo-receptive pigment, allows plants to absorb sunlight. Chlorophyll is a chlorine pigment, which is structurally similar to and produced through the same metabolic pathway as other porphyrin pigments such as heme. At the center of the chlorine ring is a magnesium ion. The molecular formula of C55H70O6N4 Mg. Hence, chlorophyll as a pigment lacks calcium.

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Robert Harding Whittaker was a distinguished American plant ecologist who was the first to pro pose the five-kingdom taxonomic classification of the world’s biota into the Animalia, Plantae, Fungi, Protista, and Monera in 1969. He also proposed the Whittaker Biome Classification, which categorized biome-types upon two abiotic factors: temperature and precipitation.

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Fructose, or fruit sugar, is a simple ketonic monosaccharide found in many plants, where it is often bonded to glucose to form the disaccharide sucrose. It is a 6-carbon polyhydroxyketone with chemical formula of C6H12O6.

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Water catchment areas such as forests are continually being destroyed through deforestation to pave way for human settlement. This problem has been brought about by rapid population increase. As a result, there is not enough rain thus causing water shortage.

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The butterfly and moth develop through a process called metamorphosis. All butterflies have “complete metamorphosis.” To grow into an adult they go through 4 stages: egg, larva, pupa and adult.