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.
Resting heart rate Age or fitness level Beats per minute (bpm) Babies to age 1: 100-160 Children ages 1 to 10: 60-140 Children ages 11 to 17: 60-100 Adults: 60-100 Well-conditioned athletes: 40-60 Your pulse usually has a strong steady or regular rhythm.