The kidneys.
The kidneys keep blood isotonic by removing excess salt and water through urine.
Phenotypically and genotypically there are only two different ratios. If you think of a Punett square...
<span>You could say that a pea plant with the trait for the dominant color green (G) could also carry the recessive trait for yellow (g). So let's say you mate a dominant green, (Gg) with another dominant green, (Gg). You would get 1 (GG), 2 (Gg) and 2 (gg). </span>
<span>Phenotypically (as in physical traitwise), the ratio is 3:1 because you have 3 green colored peas and one yellow. </span>
<span>Genotypically (as in traitwise), the ratio is 1:2:1, because you have 1 (GG), 2 (Gg) and 1 (gg). </span>
<span>So although it's random, for any specific trait there are only 4 different outcomes.</span>
Various reasons why five trained individuals might come up with different readings are - while carrying out an experiment, the accuracy with which each individual perform an experiment varies. The readings in different instruments used while performing an experiment also differs.
There is certain percentage of error that occurs while carrying out an experiment by each of the individual. Physical conditions such as temperature, pressure changes from one place to another where the experiments are being carried out.
It might involve changing to survive different temperatures such as when lakes freeze over or a lake is too hot.
<span>It is called a substrate. </span>