The pulmonary veins are the exceptions.
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The pulmonary veins are the veins that are part of pulmonary circulation and those veins transfer oxygenated blood from the lungs to the heart. <span> Two veins, one from each lung transport the blood to the </span><span>left atrium<span> of the heart.</span></span></span>
3 examples are-
1.ice wedging - when water gets into cracks, freezes and expands
2.roots-while they grow, they push rocks aside that later break.
3.animals- when they dig underground, they push rocks aside causing them to break
The type of evolutionary mechanism, genetic drift
The valves prevent the backward flow of blood.
Answer:
helping creating the double helix
