Our Combined Theory (:
Plant need both photosynthesis and respiration to survive as photosynthesis provide food for the plant during the day and respiration allow the plant to exchange gases both day and night. Without which, the plant would not be able to survive and so do the other living things.

Better theory (:
Photosynthesis is arguably the most important biological process on earth. By liberating oxygen and consuming carbon dioxide, it has transformed the world into the hospitable environment we know today. Directly or indirectly, photosynthesis fills all of our food requirements and many of our needs for fiber and building materials. The energy stored in petroleum, natural gas and coal all came from the sun via photosynthesis, as does the energy in firewood, which is a major fuel in many parts of the world. This being the case, scientific research into photosynthesis is vitally important. If we can understand and control the intricacies of the photosynthetic process, we can learn how to increase crop yields of food, fiber, wood, and fuel, and how to better use our lands. The energy-harvesting secrets of plants can be adapted to man-made systems which provide new, efficient ways to collect and use solar energy. These same natural "technologies" can help point the way to the design of new, faster, and more compact computers, and even to new medical breakthroughs. Because photosynthesis helps control the makeup of our atmosphere, understanding photosynthesis is crucial to understanding how carbon dioxide and other "greenhouse gases" affect the global climate. In this document, we will briefly explore each of the areas mentioned above, and illustrate how photosynthesis research is critical to maintaining and improving our quality of life.

Questions asked by Miss Wang (:
- Why study photosynthesis?
our theory:
We study it because we can get to know more about other functions of other living things, also get to know how our food come about and what is our food originally made from. Studying it also can let us understand more and explain to our next generation if plants doesnt exist anymore.
better theory:
Because our quality of life, and indeed our very existence, depends on photosynthesis, it is essential that we understand it. Through understanding, we can avoid adversely affecting the process and precipitating environmental or ecological disasters. Through understanding, we can also learn to control photosynthesis, and thus enhance production of food, fiber and energy. Understanding the natural process, which has been developed by plants over several billion years, will also allow us to use the basic chemistry and physics of photosynthesis for other purposes, such as solar energy conversion, the design of electronic circuits, and the development of medicines and drugs.

-What is the importance of photosynthesis?
Photosynthesis provide oxygen for all living things and take in carbon dioxide which is produced by living things. This process can help to balance the amount of gases produced in the atmosphere.

-How will photosynthesis affect us?
Without the process photosynthesis, the amount of carbon dioxide in the atmosphere would be more than the other gases. Living things need oxygen to survive and therefore, without photosynthesis, living things will not be able to survive as the amount of oxygen is used by many living things and there is no other living things is going to produce oxygen and therfore, the oxygen is slowly used up. Soon, all the living things would die.

!! COMMENT OUR THEORY (: AGREE? DISAGREE? COMMENT IN OUR TAGBOARD !!

here's a better theory of the relationship between respiration and photosynthesis ^^
http://sciences.aum.edu/bi/bi4523/student/cardwell/phvre.html