Strategies for writing an effective introduction. Start by thinking about the question (or questions) you are trying to answer. Your entire essay will be a response to this question, and your introduction is the first step toward that end.
A: Plants release oxygen as a by-product of photosynthesis, a process in which carbon dioxide is converted into sugar. The sugar is then used as an energy source for the plant. When oxygen is produced through photosynthesis, it is released by the plant into the atmosphere. The sugars produced by photosynthesis are utilized by combining them with oxygen through a process called oxidation. Photosynthesis chemically converts sunlight into energy after being collected by special cells in their leaves known as chloroplasts.
Some of the oxygen that is discharged during the photosynthesis process probably gets reabsorbed and used by the cells for respiration. During respiration, living cells, convert glucose to energy and release carbon dioxide as a byproduct. Just like animals, plants give off carbon dioxide. While it is true that there may be periods, such as night time, when some plants give off only carbon dioxide, they generally release more oxygen than they use during a 24 hour period.