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.
A normal respiratory rate for a toddler is between 25 and 30 breaths per minute; for children between the ages of 3 and 6 years, it averages between 21 and 24; and for children between the ages of 6 and 10 years, it averages 19 to 20. normal respiratory rate for an adolescent is between 16 and 20 breaths per minute. Again, be aware of the signs of respiratory distress (tachypnea, retractions, and nasal flaring) and if you observe these, initiate treatment immediately.