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Hi, I'm Jim Shields for About.com and today I'm going to teach you about photosynthesis. All organisms need energy to live. While mammals consume solid food and digest it to get the nutrients they need, how does a plant eat? The key to a green plant’s nourishment is photosynthesis. In photosynthesis, green plants and some other organisms convert light energy, in the form of sunlight, to electrical and then chemical energy. A plant needs three things for the process of photosynthesis: sunlight, carbon dioxide and water. Sunlight is gathered by organelles in the leaves called chloroplasts which contain chlorophyll, which is the substance that facilitates photosynthesis. And this is also what makes plants green. The leaves of the plant ingest carbon dioxide through holes called stomates.Water enters the plant through the roots and is delivered to the leaves through its vascular bundles, which is a system of veins that runs from the roots, through the stem, into the leaves of the plant. There are two major parts of the photosynthesis process: the light stage and the dark stage. Because it involves the conversion of light energy to chemical energy, the light stage requires light to work. The chemical energy created in the light stage is stored as a chemical called ATP. In the dark stage, carbon dioxide and ATP are converted to sugar. While this doesn’t require light, it does require the ATP from the light stage in a process called the Calvin cycle.   One vital byproduct of photosynthesis is oxygen, which is essential to our respiratory cycle.  We exhale carbon dioxide, which plants in turn require for photosynthesis, so it is complementary relationship which is key to life on earth.Thanks for watching. To learn more about biology, visit us on the web at About.com.
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