C.they separate atria from ventricles, and ventricles from the large arteries that leave them.
According to Charles Darwin's Theory of Origin of Species, an organism either develops or losses an attribute according to its adaptation to survive in a competitive environment. This is same with humans or salamanders. The loss or the retention of limbs may indicate the survival purposes of the species.
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If the disease was cause by the dominant allele, every person with said gene would be affected with the disease. if the genetic allele is recessive, both parents can be carriers (hetero) without being affected. that makes it easier for the genes to keep being passed on.
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