To rearrange its configuration to result in a complete outer shell or have a stable octet
The amount of water on the planet is fixed; it neither increases or decreases. Glaciers are sheets of moving ice. This water to form these extensive sheets must come from somewhere. The water comes from the most extensive store on the planet; the oceans. Ice Ages always corresponds to periods of low sea level because much of the ocean water is is land locked as glaciers.
The main purpose is protection. The lipid bilayer protects the cell from viruses and other threats to the cell. It also maintains homeostasis within the cell by monitoring the amount of substances the enter or exit the cell.
Though most prokaryotes have both a cell membrane and a cell wall, there are exceptions such as Mycoplasma (bacteria) and Thermoplasma ( archaea ) which only possess the cell membrane layer. The envelope gives rigidity to the cell and separates the interior of the cell from its environment, serving as a protective filter. Hope this helped!
