How many different species of living things exist today?

Why reason best illustrates why hershey and chase chose to use viruses in their experiment?

Modern whales developed their traits through natural selection what occurs during the process of natural selection

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