Question: Why are "apparently" small changes in pH so important in Biology?

Answer: pH levels are each a 10-fold change so a change by 2 is actually a change by 1000. pH determines certain characteristics in organisms that allow them to live in certain areas so an alteration in pH changes their adaption skills.

why is a change by 2 = 1000?

what would a change by 4 = ?

because it is log base10 (H+ ion concentration)

If 2 = log H+a - logH+b
then what is the ratio of H+a to H+b?

2 = log (H+a/H+b) because subtracting logs is division
https://www.thoughtco.com/definition-of-ph-in-chemistry-604605https://www.thoughtco.com/definition-of-ph-in-chemistry-604605
10 ^ 2 = 10^(log(H+a/H+b) = H+a/H+b
so a difference of 2 in pH is a difference of 100 (NOT 1000 by the way) in concentration

pH diff of 4 is 10^4 = 10,000

To understand why a change by 2 in pH is equivalent to a change by 1000, it is important to understand the logarithmic nature of the pH scale. The pH scale measures the acidity or alkalinity of a substance, ranging from 0 to 14. A pH of 7 is considered neutral, below 7 is acidic, and above 7 is alkaline or basic.

The pH scale is based on the concentration of hydrogen ions (H+) in a solution. Each unit change in pH represents a tenfold difference in hydrogen ion concentration. For example, a solution with a pH of 3 has ten times more hydrogen ions than a solution with a pH of 4, and 100 times more hydrogen ions than a solution with a pH of 5.

Now, let's examine a change by 2 in pH. For instance, if the pH of a solution changes from 5 to 3, it means the hydrogen ion concentration has increased tenfold. Because each unit change equals a factor of 10, a change by 2 results in 10 x 10 = 100. Therefore, a change by 2 in pH is equivalent to a change by 100.

Now, let's consider a change by 4 in pH. If the pH of a solution changes from 8 to 4, it means the hydrogen ion concentration has increased tenfold for every unit decrease. So, a change by 4 results in 10 x 10 x 10 x 10 = 10,000. Therefore, a change by 4 in pH is equivalent to a change by 10,000.

In summary, the logarithmic nature of the pH scale means that even apparently small changes in pH can lead to significant differences in the concentration of hydrogen ions, which can have profound effects on biological processes and the adaptability of organisms.