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Plants are one of the main forms of life, including trees, shrubs, vines, grasses, ferns, green algae, lichens and other familiar creatures. Plants can be divided into seed plants, algae plants, bryophytes, ferns and so on. It is estimated that there are about 450,000 existing species. Most of the energy of green plants is obtained from sunlight through photosynthesis, and temperature, humidity, light and fresh water are the basic needs of plant survival. Angiosperms have six organs: roots, stems, leaves, flowers, fruits and seeds. Green plants have the ability of photosynthesis-with the help of light energy and chlorophyll.