The balance between rates of sympatric and allopatric speciation is governed by mutation rates. Opportunities for geographic isolation are a key component of the speciation process. Rates of speciation are correlated with the net total land area available. Allopatric speciation tends not to occur on islands. Each island hosts sympatrically speciating populations.

the oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. this blood then enters the left atrium, which pumps it through the mitral valve into the left ventricle. from the left ventricle, the blood passes through the aortic valve to the aorta.

deoxygenated blood leaves through the right ventricle through the pulmonary artery. from the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle.