Will mark brainliest! After you have finished reading the passage, describe in your own words what natural selection means in the box below. Give one example of how an animal's environment can influence the method it uses to reproduce.

The person who utilize the progression principle will keep adding the difficulty of the exercise that he's doing, while the person who does not, will only stay stagnant.  the person that utilize progression principle, will get a stronger endurance because now his body is conditioned to do harsher routines.{the answer was already on verified)

Target heart rate is the answer