Which famous scientist introduced the idea of natural selection?

Johnny rode his bike 4 blicks down the street to his friend's house once he got to his friend house and realized he could not cone out to play he turned aroubd and went back home. what is 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

Acommon kind of mechanical weathering is called

Long-period comets come from the oort cloud particles in earth’s atmosphere material from the asteroid belt the kuiper belt