Study Online and Download KIPS 9th Class Biology Notes Unit 9: Transport.
Study Online and Download KIPS 9th Class Biology Notes Unit 9: Transport. We know that life of organisms is the product of complex metabolic processes occurring in them. In order to run their metabolism, cells need some materials from environment and also need to dispose some materials into environment. For this purpose, materials are transported to and from cells.
One method for the movement of molecules is diffusion but it alone cannot fulfill the needs. It takes much time for materials in solution to diffuse even a few inches. For the molecules of materials, diffusion can work only in unicellular and simple multicellular organisms, because every corner of their body is in close and direct contact with environment. In complex multicellular bodies, cells are far apart from environment and such bodies need a comprehensive system for the transport of materials.
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