Question

The heart rates of an elephant, a human and a mouse are nearly 25, 72 and more than 200 per minute respectively. (i) What conclusions can you draw from these observations? (ii) What is the significance of these different heart rates?

Answer 1

Hint: The heart rate also known as the pulse is the number of times the heart beats in a minute. It varies among different organisms as well as among humans. In the case of humans, the average heart rate is 72 beats per minute but can change or vary in different conditions.

Complete Answer:
(i) The heart rate of an organism is independent to its size. As the heart rate of a small animal is about 200 times per minute, the heart rate of a human being who has an average body weight is around 72 beats per minute. The heart rate of a huge size elephant is about 25 beats per minute. So, from this, we can conclude that the larger the size of an organism the slower is the heart rate and smaller the organisms the faster is the heart rate.

(ii) This difference in heart rate due to the size makes an importance in the metabolism. Metabolism is the sum total of all the chemical reactions occurring in the living body. It can be of two types- anabolism and catabolism.
- Anabolism refers to the making up of metabolic products whereas the catabolism refers to the reactions which involves breaking up. This metabolism plays an important role in the body size. The heat evolution occurs during the metabolic processes.
- The heat evolved in small sized organisms evolves at a faster rate. So, to maintain their normal body temperature they have to burn more calories. This respiration process which requires more breakdown of calories requires more oxygen. So, this requirement of the oxygen is fulfilled using faster heart rate in small animals.

Note: In larger animals, the metabolism plays an important role. The larger animals release heat at a slower rate. So, there are no greater oxygen requirements. Thus, the heart rate of such organisms is much slower. The same principle is applicable in case of human babies which have faster heart rate as compared to adults.