Nitrogen And Oxygen

At least how many types of organisms inhabit the earth? The measure of the variety of organisms present in different ecosystems is called what? How many types of plants are known to biologists? Biological classification is a method by which whom divide orgnisms into groups and subgroups? Nitrogen is a member of group VA in the periodic table? Pure Nitrogen is slightly heavier than air? Nitrogen is chemically inert at higher temperature? Haber process is used in the preparation of nitric acid? Sodium and potassium react with oxygen vigorously at ordinary temperature? In peroxides the valence number of oxygen is -1?