What is an example of quantitative variation?

Has regulatory areas for thirst, hunger, body temperature, water balance, and blood pressure

There are few cells in the body that do not undergo mitosis: most somatic cells divide regularly, some more than others. take for example the cells that line the digestive tract. these cells must be frequently replaced because they are constantly eroded by the movement of food through the tract. what mechanism(s) is/are in place to ensure that these cells are exact copies of the mother cell

Which fossil organism in whale evolution do you think was the first to live mostly in water? explain your claim with evidence and reasoning?