Answer:
The reaction rate of the digestion helps in understanding which part of the digestive system having trouble in digestion especialy stomach and intenstine related.
It involves the fact that most of the enrgy or calories are get by the small intestine and also vitamins and minerals are absorbed by this part of the digestive system so if the small intestine is having problem the rate of digestion would be affected and and an individual could be malabosrbed.
If the problem lies in the stomach it might show some effects of a poor digestion, however the rate of digestion would be better than if the problem lies in the small intestine.
The answer to this question would be: by producing buffer
The pH of optimal growth of bacteria might be different. Some bacteria can grow in an acid condition called acidophile, other live in base condition called alkaliphiles and the rest live in neutral pH condition called neutrophiles. The bacteria can maintain their internal pH by producing acid, base or buffer. If the surrounding pH is too acid, the bacteria can reduce the H+ concentration by producing base. If the condition is too alkali/base, the bacteria can produce acid by doing fermentation.
Environment, predators, and natural selection.
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Concentration gradient across the membrane. Proteins in the membrane allow specific molecules through, passively.
