Observe fish in an aquarium. They open and close their mouths and the gill-slits (or the operculum which covers the gill-slits) behind their eyes also open and close. Are the timings of the opening and closing of the mouth and gill-slits coordinated in some manner?
(ii) Whether the number of times the fish opens and closes its mouth in a minute is faster than to the number of times you breathe in and out in a minute?
The timing of the opening and closing of the mouth and gill-slits in a fish are coordinated.
Reason: The water engulfed from the mouth is immediately pushed to gills for absorbing oxygen dissolved in water, into blood. It is then removed by gill-slites.
(ii) The number of times the fish opens and closes its mouth in a minute is much faster than the number of times we breathe.
Reason: The amount of dissolved oxygen in water is very low. The fish opens and closes its mouth (to push water over the gills) more number times so that more and more water passes over the gills. So that sufficient oxygen can be absorbed by the blood in the gills to meet the body's requirement.
