How does the usable form of nitrogen enter our bodies?

The most common form of nitrogen in your body is proteins containing mainly carbon, hydrogen, oxygen and nitrogen. While neither humans nor animals can get nitrogen into their bodies from the air or soil, they do gain nitrogen from vegetation

Explanation:

the core of the sun is so hot and there is so much pressure, nuclear fusion takes place, hydrogen is changed to helium. nuclear fusion creates heat and photons. when the heat reaches the earth it warms the molecules of the atmosphere, and they warm other molecules and so on.

then that particular organisms become extinct.