Where do the oxygen atoms for the o2 gas that we breathe come from? light water carbon dioxide sugar

What form of anesthetic was used for field surgery

Which of the following statements is true about the relationship between genetic variation and natural selection? a. genetic variation must be present in a population before natural selection can act on it. b. genetic variation arises in a population as a result of natural selection. c. natural selection can act on a population whether there is genetic variation within the population or not. d. after natural selection acts on a population, the amount of genetic variation in the population always increases.

49 ! how are energy cycles and growth cycles related?