Asked by: Kirsty Nesbitt, Waterlooville
The skin of an unripe banana is full of water. Although the skin is quite watertight on the outside, water is gradually lost from the skin by osmosis to the fruit inside as the banana ripens. This causes the skin cells to wilt and collapse, making the overall skin thinner and more pliable. This is probably an adaptation to make the fruit easier to eat when it is ripe, thereby encouraging seed dispersion.