As a molecule of oxygen passes from pulmonary alveolar air into the blood it passes through the layers of the respiratory membrane in what order

What are two reasons for why a species might disappear from the fossil record?

Identify the missing parts of the carbon cycle

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