<span>The RNA world is the hypothesized format of chemical life that existed prior to our current DNA and RNA world. In the RNA world, RNA molecules formed in the primordial soup and began to evolve by self-replication and mutation. This led to increased complexity, natural selection of "better" RNA and diversification of RNA based life.</span>
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 :)
I hope u understood!
