Because if the cells wouldnt be replaced then after a cell dies (which happens very rapidly) we wouldnt exist for very long. the body replaces tons of cells on a daily basis, and if the body stopped making new ones to replace the old, we wouldnt have anymore living cells left in our body.
I think stream bank. It grows in moist places and wetlands, and is especially abundant along streamsides and riparian areas at elevations below 1400 m.
