Before there was any life on earth, which gas was absent from earth’s ancient atmosphere?

What function does a limb serve in each animal how are the limb bones of the four animal similar based on the similarities what can be inferred about the evolution of the poor animals

What condition is kept close to its set point in osmoregulation? a. body temperature b. platelet count c. blood glucose level d. water balance

What is the primary function of the nervous system?