Specialized cells, called t cells, are first to react in the human body when there is a viral attack.

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.

on island x the species needed to adapt because they were being subject to predators which didn't inhabit island y.