Scientific American, Volumen223

accelerator acid agricultural amino acid amount animals anorthosite atmosphere atoms behavior biological biosphere calcitonin calcium carbon dioxide cells chemical chloroplasts color cycle diameter Durrington Walls earth ecosystem effect eggs electrical electrons energy engineering environment environmental experiments film flow fuel genes genetic heat helium hormone hydrogen illustration increase industrial input ions kilograms laboratory land laser layers liquid lunar magnetic mass measure ment meter metric million mitochondria molecules multiple sclerosis neurons nitrogen nodes nuclear nutrients ocean organelles organic output oxidation oxygen palindrome Pangaea parathyroid hormone particles percent photosynthesis plants plastron pollution population problem production protein radiation radicals reactions reactor result SCIENTIFIC AMERICAN soil solar species stars structure sulfur surface synaptic temperature tion tube ture units University vapor viscosity voltage