1 84 - The Cell 



CARBON DIOXIDE 



N AIR AND NATURAL 



SPlRATlON 



CO, 



R ES P I RAT I O M 



MIMA 



CARBON (ORGANIC) 



COMPOUNDS IN THE 



ENVIRONMENT 



IN DEAD ORGANISMS 



AND THEIR 



REMNANTS 



Fig. 10-9. The cyclic usage of carbon compounds in various organisms, i.e., the carbon cycle. Compounds not 

 included in the circles are free in the environment. 



->NITRATE 



5ALT5^ 



Fig. 10-10. The cyclic usage of nitrogen compounds in various organisms, i.e., the nitrogen cycle. Compounds 

 not included in the circles are free in the environment. 



