Which statement about fossils could be used as evidence that
evolution by natural selection has been in effect for millions of
years?
Fossils found in higher layers of rock are older than those
found in lower layers.
Fossils found in lower layers of rock are more complex than
those found in higher layers.
© Fossils of current species have been found throughout rock
layers that are billions of years old.
0 Fossils of species that no longer exist but are ancestors of
current species have been found in rock layers.

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.

the scientific method.