Biology MCQs

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The human brain sends messages to other parts of the body through a network of connecting wires (neurons) called the nervous system. Neurons carry messages in the form of electrical signals called nerve impulses. The human brain contains about 100 billion neurons.

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The structure of B12 is based on a corrin ring, which is similar to the porphyrin ring found in heme, chlorophyll, and cytochrome. It contains the biochemically rare element cobalt sitting in the centre of the ring. Also called cobalamin, it is a water-soluble vitamin.

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Drones are male honey bees. They develop from eggs that have not been fertilized, and they cannot sting, since the worker bee’s stinger is a modified ovipositor (an egg laying organ). Drones die soon after mating with female partner.

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Leech is an ectoparasite. It secretes the anticoagu lant hirudin and feeds on the cattle’s blood hence called sanguivarous. These are class of animals which feed on blood.

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For keeping the stomata open a constant expenditure of energy is required. This is required for conversion of starch to sugar. The stomatal opening is, in turn, related to transpiration which is the evaporation of water from plants. It occurs chiefly at the leaves while their stomata are open for the passage of CO2 and O2 during photosynthesis.

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Thymus gland also called a degenerating gland as it starts its degeneration form an age of 17-18 years onward is the site of lymphocytes called Tlymphocytes to provide defense to body. A lymphocyte is a type of white blood cell that is part of the immune system. There are two main types of lymphocytes: B cells and T cells. The B cells produce antibodies that are used to attack invading bacteria, viruses, and toxins.

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An allosome is a sex chromosome that differs from an ordinary autosome in form, size, or behaviour. The human sex chromosomes are a typical pair of allosomes. In typical ovum, there is a pair of X-chromosomes while sperm has X and Y chromosome each.

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Cholesterol is defined as a waxy alcohol, fat-like substance that occurs naturally in all areas of the human body. 100-200 mg/dL is considered as normal for the human beings. The total cholesterol counts below 180 mg/dl increase the risk for haemorrhagic stroke; and above 200 mg/dl may be normal and healthy for some people, as the ratio of LDL to HDL cholesterol is considered a more important factor in prediction of disease risk particularly heart disease.

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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.

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The word ecology was coined by the German zoologist Ernst Haeckel, who applied the term oekologie to the “relation of the animal both to its organic as well as its inorganic environment. The word comes from the Greek oikos, meaning “household,” “home,” or “place to live.” Thus, ecology deals with the organism and its environment.