The total mass of all living things on Earth is 545 Gigatons. Part (a) Single-celled bacteria and archaea have a total mass of 77 Gigatons. 77 Gigatons is what percentage of the total mass of all living things? Part (b) Plants have a total mass of 450 Gigatons. 450 Gigatons is what percentage of the total mass of all living things? Part (c) Humans have a total mass of 0.06 Gigatons. 0.06 Gigatons is what percentage of the total mass of all living things?.