Humans ferment lactic acid in muscles where oxygen becomes depleted, which is why sometimes if you finish a run and don't stretch soon you have have discomfort. <span />
Answer:
There is no mixing of oxygen-rich and oxygen-poor blood.
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The right atrium and right ventricle of the human heart pump oxygen-poor blood to the lungs and the left atrium receives oxygen-rich blood. They never mix.
Answer:
Even a slight reproductive advantage will eventually lead to the elimination of the less well adapted of two competing species
Explanation:
The competitive exclusion describes relationship between two species that compete for the limiting sources, and cannot coexist. It is enough for one species to have slightly advantage to be dominant over the other. As a consequence, other species (the weaker one) will be extincted (shift to a different ecological niche).
