Activity 6.6 NCERT class 10 science chapter 6 Life processes
Activity 6.6 asks us to look at gills and mouth of fishes and observe how many time they open and close in a minute.
The breathing rate of fish is more than us.
Organisms like fishes, animals and humans require oxygen to meet its energy demand. They do this by taking either oxygen dissolved in water as in fish or oxygen present in air by the lungs.
Oxygen is not highly soluble in water. Due to this the amount of oxygen in water is lesser (9mg/ltr). So to meet the demand for oxygen fish opens and closes its mouth and gills more frequently which is around 90 to 100 times a minute.
Atmospheric air contains a significant amount of oxygen (21%). So we need a lesser rate of breathing to fulfil our needs. As a result, human respiratory rate is only 12 to 20 breaths per minute.