The pumping of the heart involves the alternate contraction and relaxation of the chambers of the heart. the upper chambers of the heart all called ( ), and the lower chambers of the heart are called ( ).

Astudent is looking through a microscope at some cells of an onion root tip. many of these cells are undergoing division since the root tip grows quickly and requires more cells. which cell most recently underwent metaphase? w x y z

Which of the following describes the difference in stimuli required to detect a difference between the stimuli? a. just noticeableb. signal detectionc. subliminald. top down

Everything in the universe originated from a single point. how was it possible for everything in the universe to have occupied a single point in space?