Adaptations-. Black bears have a thick layer of fur for the cold winters,claws to climb trees and stay away from danger along with sharp teeth for protection like scaring away predators and to tear apart fish.Bears also hibernate in the winter to avoid having to find food which is difficult in the winter.
The cell membrane, or plasma membrane, surrounds and protects the internal environment of a cell; however, this is not its only function. A cell membrane also determines what materials enter or leave the cell. This ensures that the cells will be able to get rid of wastes and take up important nutrients and gases.
Plasma Membrane. All living cells, prokaryotic and eukaryotic, have a plasma membrane that encloses their contents and serves as a semi-porous barrier to the outside environment. The membrane acts as a boundary, holding the cell constituents together and keeping other substances from entering.The plasma membrane is permeable to specific molecules, however, and allows nutrients and other essential elements to enter the cell and waste materials to leave the cell.he membrane acts as a boundary, holding the cell constituents together and keeping other substances from entering. The plasma membrane is permeable to specific molecules, however, and allows nutrients and other essential elements to enter the cell and waste materials to leave the cell.