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.
The average maximum heart rate is calculated to be 200 for a 20 year-old and then drop 1 beat per minute for every year over 20 until at age 70, where the average maximum is set at 150 beats per minute. Another way to figure your maximum heart rate is to subtract your age from 220 and use the resulting number.