Photosynthesis is vital for maintaining levels of atmospheric oxygen.

This is true. Photosynthesis plays a vital role in maintaining the levels of oxygen in the atmosphere. Oxygen is a byproduct of photosynthesis

Oxygen is crucial for the survival of most terrestrial and marine animals including man.  The level of oxygen in the atmosphere is about 21%. The process of photosynthesis helps in maintaining this balance. Plants absorb carbon dioxide and produce oxygen.

Without photosynthesis , life on earth would come to a halt. The process of photosynthesis was first discovered, albeit partially, in the 1600s by Jan Baptista van Helmont

people cluster in places that have rich soil, fresh water, and mild climates.

explanation:

landlessness of ordinary people

^^something like that^^^