Quiz 40: Digestion and Human Nutrition


Operculum is a bony flap that covers and protects the gills. In Indian yellow-tail angelfish, operculum is vital in obtaining the oxygen. These open and close alternately. When the mouth of the fish closes, operculum opens that leads to the drop of pressure inside the fish. This allows the fish to absorb some amount of oxygen from water across the gill's lamellae. Thus, it enhances the rate of oxygen diffusing inside the fish and carbon dioxide diffusing out of it. Hence, operculum helps in increasing the rate of absorption of oxygen.

Atmosphere consists of different concentrations of various gases. Composition of gas is as follows: • Nitrogen-78% • Oxygen-21% • Carbon dioxide-0.04% • Other gases-0.04% Thus, nitrogen is the most abundant gas in the atmosphere. Hence, the correct option is (a) 'nitrogen'. Nitrogen is the most abundant gas in the atmosphere followed by oxygen. Hence, option (b) 'oxygen' is incorrect. The concentration of carbon dioxide in atmosphere is 0.04%. Hence, option (c) 'carbon dioxide' is incorrect. The major constituents of atmosphere are nitrogen (78%) and oxygen (21%). Hence, option (d) 'hydrogen' is incorrect.

b) Difference between pharynx and larynx: img Hence, pharynx and larynx are different. c) Difference between bronchioles and bronchus: img Hence, bronchiole and bronchus are different. d) Difference between pleural sac and alveolar sac: img Hence, pleural sac and alveolar sac are different.

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