DENDROLOGY

Detailed explanation-1: -Photosynthesis is the process of synthesis of food by plants using carbon dioxide and water in presence of sunlight and chlorophyll. Oxygen (O2) is released during the process as a waste product. Hence, oxygen is not essential for the process of photosynthesis.

Detailed explanation-2: -The correct answer is ‘photosynthetic bacteria’.

Detailed explanation-3: -Photosynthesis converts carbon dioxide and water into oxygen and glucose. Glucose is used as food by the plant and oxygen is a by-product. Cellular respiration converts oxygen and glucose into water and carbon dioxide. Water and carbon dioxide are by-products and ATP is energy that is transformed from the process.