Aristotle is the father of biology
100,000 years ago is your answer
If a cell membrane became impermeable, instead of selectively permeable, the cell would not remain alive, though certain organisms would be able to stay alive longer than others. This is because the cell membrane allows essential molecules and substances such as oxygen into the cell, while allowing harmful substances, like waste, out of the cell.
:)
In mitosis (regular cell division)
the cell (mother cell) duplicates it's DNA and aligns it down the center of the cell, so that when it splits each new cell (daughter cell) gets the exact DNA as the mother cell