What is the main purpose of controlled variables in an experiment?

Johnny rode his bike to a friend's house 4 blocks down the street in his neighborhood. he immediately rode back home once he realized his friend was not able to play. what was his displacement for the total bike ride? how did you determine this? what could we use as a reference point to determine he was in motion during his bike ride? why can you use it as a reference point

Match the description of each organism to the appropriate category

Which is one example of a phenotypic change that is not genetic