The wind is just strong enough to move the sand grains which were sorted by size by the wind. Heavier grains were left in place where as smaller grains were carried away. These grains kept moving till they were concentrated in one place usually up a hill. The grains climb the flat slope on the windward side and then fall off the steep side. The dunes may migrate slowly as this process continues, the grains at the upwind side climb the dune with the help of the wind and then fall down the downwind side.<span>
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In a chemical reaction, the atoms and molecules that interact with each other are called reactants. In a chemical reaction, the atoms and molecules produced by the reaction are called products. In a chemical reaction, only the atoms present in the reactants can end up in the products.
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14. Dermis
15. Chemical
17. Virus
18. Antibodies
19. Gas exchange
20. Ligament
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Spherical shaped bacteria are known as coccus bacteria.
