Biology MCQs

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Phosphorus is required for nitrogen fixation by Rhizobium. This is a genus of Gram-negative soil bacteria.

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The principal chemical component of vegetable fibres is cellulose, with varying amounts of lignin and hemicelluloses also usually present; thus, the fibres are also referred to as cellulosic or lignocellulosic. Examples include cotton, hemp, jute, flax, ramie, sisal, bagasse, and banana. Vegetable fibres are usually stiffer but less tough than synthetic fibres.

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Cecum is a pouch connected to the junction of the small and large intestines. It is a large tube-like structure in the lower abdominal cavity that receives undigested food material from the small intestine and is considered the first region of the large intestine. It is separated from the ileum (the final portion of the small intestine) by the ileocecal valve (also called Bauhin valve). The main functions of the cecum are to absorb fluids and salts that remain after completion of intestinal digestion and absorption and to mix its contents with a lubricating substance, mucus.

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Viruses, bacteria and fungi multiply very quickly, while worms multiply very slowly in comparison. Taxonomically, all bacteria are closely related to each other than to viruses and vice versa.

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A Barr body is the inactive X chromosome in a female somatic cell in those species in which sex is determined by the presence of the Y or W chromosome rather than the diploidy of the X or Z. A typical human female has only one Barr body per somatic cell, while a typical human male has none.

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Crabs come from the same family as lobsters, crayfish, shrimp, krill and barnacles, as all are in the subphylum crustacea. They are also in the phylum Arthropoda, which includes insects, arachnids and crustaceans. They are decapods (having ten legs) and form an order within the decapods, called the Brachyura.

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Haptens are small molecules that react with a specific antibody but cannot induce the formation of antibodies unless bound to a carrier protein or other large antigenic molecule. They are incomplete or partial antigens.

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Phototropism is the growth of organisms in response to light. In plants, phototropism is a response to blue wavelengths of light and is caused by a redistribution of auxin from the illuminated side to the darker side of the shoot, resulting in quicker growth on the darker side and bending of the shoot toward the source of light.

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The cerebellum is known as little brain. It is a region of the brain that plays an important role in motor control. i.e. in maintaining and coordinating body posture at different times of the day/night.

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The term xerophyte refers to a plant species that has evolved over time to adapt to dry and arid regions like deserts. Xerophytes have adapted to be able to keep extremely large amounts of water for a long period of time. Without this capability, the plant would die, as the desert region itself does not provide enough water to sustain life. They have thick cuticle, sunken stomata and leaves modified in form of spines such as in opuntia.