Explain how oxygen enters your body and is used. make sure you mention the organs used, chambers of the heart and in which direction the blood goes.

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

Explain how the number of similarities between the embryos from early stage to late stage is used as evidence of a common ancestry

Is there any species that went extinct in recent years due to natural causes (not caused by human interaction). if so, what caused it?