Natural selection allows nature to chose which species survives. Only the fittest get to pass on their genes. And by fittest i mean the ones that are better adapted to the environment.<span />
Circulatory system pumps blood from the heart to the lungs to get oxygen. The heart then sends oxygenated blood through arteries to the rest of the body. The veins carry oxygen-poor blood back to the heart to start the circulation process over. Your circulatory system is critical to healthy organs, muscles and tissues.
Yes, rennin<span>. [ren´in].: the milk-curdling enzyme found in the gastric juice of human infants ... was formerly used extensively as a </span>curdling agent<span> by the cheese industry.</span>
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