A researcher is observing human muscle cells through an electron microscope. They notice that cells from a more physically active individual
contain more of a certain organelle than those of a less active individual.
Which organelle are they observing?

What is thought to have caused the mass extinction at the end of the cretaceous period?

Which of the following is not a defining characteristic of plants?

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