In the domain system of classification, prokaryotes are divided into two domains: bacteria and archaea. the two domains differ in all but one feature. that is, both

That is, both have prokaryotic cells

The two prokaryotic domains differ greatly but all organisms in these domains have prokaryotic cells. Members of the domain Archaea live in extreme environments, including anaerobic conditions. Also, the Archaea have cell walls that are different from the Bacteria as their walls do not contain peptidoglycan. Some scientists believe the Archaea to be more closely related to the eukaryote.

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.