Natural selection could not occur without environment, and a act on animal.
If it cannot avoid it, it just find a mechanism to use oxygen and make it less harmful to itself. This is how the process of cellular respiration may have evolved
Carbohydrates are not important as a stimulus in the gastric phase of gastric secretion, whereas distension, peptides, and low acidity are.
<span>Commensalism is an interaction in which one of those species would benefit, and the other one would not be affected. Parasitism is an interaction in which one of those species would benefit at the expense of the host organism. Thus, in commensalism we have one positive and one neutral result while in parasitism we have one positive and one negative result.</span>
I think the answer is D but it's been a while since I've done this.
