It took 1,649 years for the population to double ,going from 0.25 billion people to 0.50 people. How long did it take for the population to double a second time ?

where in your body is there an enzyme that does function at a high or low ph? what is the name of that enzyme and its function?

radon is correct hope this

these muscles maintain the blood pressure in the vessels. the smooth muscles are innervated by nerves of the autonomic nervous system. when the muscles contract, they cause vasoconstriction of the vessels and increase blood pressure. when the muscles relax, they enable vasodilation of the   blood vessels hence reduce blood pressure.