Tortoises with long necks were found to be abundant in regions that had vegetation on a higher level. a few years later, drought hit the region and the vegetation dried up. over time, grasses were observed in the region. shortly thereafter, an increase in short-necked tortoises was observed in the region. what does this change in the species of tortoises suggest?

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.