Plants are the major and primary source of food and oxygen. Plants are called producers as they make their own food with the help of inorganic compounds present on earth.
The only source of oxygen in the atmosphere is planted.
If there were no plants on the earth, there would be no oxygen to respire, and there will be no food.
The atmosphere of the earth will also get affected, and the temperature will rise.
With no food and oxygen, the organism wouldn't be able to survive