Explain why living organisms contain more hydrogen atoms than any other atoms, yet 65% of a typical organism’s mass is oxygen.

The reason is that Oxygen atoms contain 16 times more mass than Hydrogen atoms.

Hydrogen H11 Has only one proton and no neutrons and so has an atomic number of 1 and a mass of 1

Oxygen O168 Has 8 protons and also 8 neutrons and having atomic number of 8 and a mass of 16.

Hydrogen takes 16 Hydrogen atoms to equal the mass of 1 oxygen atom.

"1. it should be, it has been for about 20 years, and it's really not much different in the end than breeding animals to have particular traits. there are always concerns about genetically engineered animals/plants affecting the environment in unexpected negative ways, but i can't think of an example where the fears didn't turn out to be baseless.  

first, as you point out, it would be a great advance in pharmacology, to be able to tailor drugs and their doses to me. the pros involve better medical treatment. the cons involve privacy issues like insurance companies denying coverage to people with genetic risk factors. looking at dna markers wouldn't affect the frequency of genetic diseases, but it would allow detection of them earlier. and ok, actually i suppose that if people used this information to avoid having children with genetic diseases, some might decrease in frequency."