This proportion of heavy - to - light carbon typically occurs only in living organisms. (sciencenewsforstudents.org)
It will also be stripped inside, with the rear seats removed completely and the electronically operated front seats replaced with a stiff, light carbon shell covered in thin padding. (motoring.com.au)
So if the fraction of lighter carbon isotopes in the atmosphere is increasing, we know the increase is due to burning plants and fossil fuels, and that is what scientists observe. (skepticalscience.com)