Have you ever taken the time to thank a leaf? It may seem silly to thank leaves, but we need them to survive. In fact, we could not survive without the energy made by leaves through the chemical change called photosynthesis. Life on Earth relies on light energy captured from the Sun. Photosynthesis changes this energy to the form vital for humans. This is how we get energy from food. Some forms of energy used by humans also come from photosynthesis. There are other benefits to the process. Photosynthesis helps maintain the level of oxygen in the air the humans need to survive. All of this occurs in leaves!
During photosynthesis, the chlorophyll in leaves captures energy from the Sun. Photosynthesis changes this radiant energy to chemical energy. Chemical energy is the form used by all living organisms. Photosynthesis changes water and carbon dioxide with radiant energy. A form of sugar called glucose is made. Plants need glucose to live and grow. Extra glucose is stored in the plant as a carbohydrate called starch. When animals eat plants, they get energy from the stored carbohydrates in the plant. Therefore, all energy that animals get from food comes first from photosynthesis. This is true even for animals that are carnivores, or meat-eaters. The energy is passed to them through the food chain. Without photosynthesis, there would be no food. Animals, including humans, would not survive.
Some forms of energy come directly from photosynthesis. Have you ever sat around a campfire or the fireplace in your home on a wintry evening? If so, you have felt heat energy from photosynthesis. Wood and other hard plant material are carbohydrates made from glucose. Burning changes the chemical energy stored in wood into heat. Another form of energy that comes from photosynthesis is ethanol. Ethanol is made from sugars and starches. Ethanol is used in gasoline in Brazil and the United States.
During photosynthesis, carbon dioxide is taken from the air. Plants make oxygen as a byproduct. Humans, and many other organisms, can only survive in environments with oxygen. Through respiration, we take in oxygen and release carbon dioxide into the air. Humans need the oxygen made by plants to live. We also make carbon dioxide that plants need for photosynthesis.
For humans, it is essential that photosynthesis changes energy from the Sun into chemical energy. Our lives rely on the results of photosynthesis. That’s why the next time you see a leafy green tree, or a leafy plant, you might want to say, “Thank you!”
