Survival of the fittest  is a phrase that originated from an evolutionary theory as a way of describing the mechanism of natural selection. The biological concept of fitness is defined as reproductive success.
The normal respiratory rate is 30 to 60 breaths per minute from birth to one year, 24 to 50 breaths per minute from one to three years and 22 to 34 breaths from three to six years old. As the child moves into school-age, the normal respiratory rate slows. From age six to twelve, the normal rate is 18 to 30 breaths per minute, while 12 to 16 breaths is the normal rate from age 12 to 18.
Heart rate tends to decrease across childhood up to adolescence. Age norms for resting heart rate are available at We Be Fit. There is significant variability in childrenâs heart rates even within age groups. Newborns have heart rates that range from 100 to 160 beats per minute (bpm).Children from ages 1 to 10 have heart rates than range from 60 to 140, and average from 85 to 90. Children who are 11 to 17 have heart rates that range from 60 to 100 bpm.eart rate tends to decrease across childhood up to adolescence. Age norms for resting heart rate are available at We Be Fit. There is significant variability in childrenâs heart rates even within age groups. Newborns have heart rates that range from 100 to 160 beats per minute (bpm).