what is the physiological reason for the difference in adult male/female heart rates ?

Answer 1

Whether male or female, the amount of blood the heart has to pump round the cardiovascular loop varies roughly as body mass, and this is "cardiac output", about half a wineglass full is average, - so, say 70 beats per minute gives a total flow on average, of about 5 litres per minute.
But there are big fellas with big hearts, and little fellas with big hearts, and big girls with big hearts and small girls with big hearts, and every combination in between, of fellas and girls and big or small hearts. You name it.

On average, of course, most people have a heart that's tailored to their body mass, and will pump out an average volume at each stroke (or beat). So, although the cardiac output for a woman probably needs to be less than for a man, -because she's smaller, her (average normal) heart probably pumps out less than a man's at each stroke. (Say 60mls instead of 70mls....._)
This won't do, so her heart has to beat more times per minute.
So, multiplying pulse rate by stroke volume gives the right cardiac output, for HER.
It's not a hard and fast rule, of course, and girls with big hearts can have slow pulse rates, and deliver the same outputs. And vice versa.
So, it's not simply question of size, and scale, as stated above,(- although what she says is perfectly true).
It's a question of the combination of pulse rate and stroke volume in comparison with the systemic flow of blood required by the individual.

Answer 2

The source of energy in our body are cells which brake down the food to create energy with help of oxygen. As the body muscles work, they cells need to provide them with energy, which in turn requires more oxygen. The blood is the medium which carries oxygen from the lungs to body cells. As the oxygen requirement increases, the flow of blood needs to increase. So the heart starts to pump blood faster and you feel the heart rate increasing... My english isn't that great (I'm from India) but hope this helps.

Answer 3

Usually, the smaller a person or organism, the faster their heart beat
females are generally smaller than males
example- mice can have a heart beat of 300 per minute, while whales have a heart beat of once per hour