Which gas is taken up by man and animals during respiration ?

The organism and the physical environment of the habitat form an ecological complex called :

Study of inter-relationship of organs and their environment is called :

Which is an essential element required by organisms to synthesize proteins and nucleic acids ?

Which is the biggest storehouse of water ?

Name the process in which the ammonia is converted into nitrites and nitrates ?

The nutrient element derived from the earth by the living organisms for the use in their growth and development are called :

The life sustaining zone of earth, where lithosphere, hydrosphere and atmosphere interact is called :

During photosynthesis which gas is liberated in the atmosphere ?

Among the following which is a nitrogen fixing bacteria ?