trees do not fix N2 from air they fix oxygen with the help of N2 fixing bacteria . so trees do not fix N2
Primary Succession is when an ecological community experiences a community changing natural disaster (volcano, glacier, etc) primary succession starts from bare rock. Secondary succession starts from pre-existing soil, and occurs from a hurricane, deforestation, etc.
As we inhale air, oxygen enters the respiratory system and the circulatory system to transport it to the other parts of the body and to all cells. As the oxygen is already transported, the blood becomes deoxygenated and carries a CO2 which returns to the lungs and then we exhale the carbon dioxide.
