Correct Option
The correct option is (a).
Explanation
Photosynthesis is the physicochemical process by which green plants, algae, and certain bacteria transform light energy into chemical energy. This process involves the synthesis of organic compounds (food) from inorganic raw materials, primarily carbon dioxide and water, in the presence of sunlight and chlorophyll.
Statement-wise Analysis
- Statement 1 is Correct: Plants are autotrophs, meaning they synthesize their own food. Through photosynthesis, they convert light energy into chemical energy stored in the bonds of carbohydrates (glucose). This forms the basis of energy flow in ecosystems.
- Statement 2 is Incorrect: During photosynthesis, plants absorb carbon dioxide (CO2) from the atmosphere and release oxygen (O2) as a by-product. Carbon dioxide is a raw material consumed in the process, not the primary gas produced.
- Statement 3 is Incorrect: While plants do consume oxygen for cellular respiration (which occurs day and night), the amount of oxygen produced during photosynthesis (which occurs only in the presence of light) significantly exceeds the amount consumed in respiration over a 24-hour cycle. Consequently, plants are net producers of oxygen and net consumers of carbon dioxide.
Key Takeaway
Photosynthesis converts carbon dioxide and water into glucose and oxygen using light energy. It is the primary process responsible for maintaining the balance of atmospheric oxygen and carbon dioxide, with oxygen production exceeding respiratory consumption in growing plants.