How would a scientist have made the distinction between a unicellular and a multicellular organism in the 17th century(1600s), the mid-20th century(1900s), and in the 21st century

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

Which statement is true for bacteria a. bacteria have complex internal structures b. all bacteria are spiral in shape c. all bacteria cause disease in animals d. bacteria break down some foods

This rapid change in species that rarely leaves behind fossil evidence is referred to as