Why do living things depend on diffusion?

Living organisms obtain many of their requirements by diffusion. They also get rid of many of waste materials in this way. For example, Plants need carbon dioxide for photosynthesis. This diffuses from the air into the leaves through the stomata. It does this because there is a lower concentration of carbon dioxide inside the leaf as the cells are using it up. Outside the leaf in the air, there is a higher concentration. Carbon dioxide molecules therefore diffuse into the leaf down this concentration gradient :)
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The truman doctrine was an american foreign policy whose stated purpose was to counter soviet geopolitical expansion during the cold war. it was announced to congress by president harry s. truman on march 12, 1947, and further developed on july 12, 1948, when he pledged to contain threats to greece and turkey

Very minute and important evidence needs to be collected in order together detail and figure out what had happened