It's similar in the sense that when an ecosystem is challenged above its initial capacity, so can roads be challenged over their carrying capacity. When this happens, an ecosystem/roads "break down" start worsening the function they were supposed to do and in general become worse and worse.
Swamp ... Hope this helps :)
The answer should be Groundwater.
Chromosomes are turned on or off. Ex. genes for karatin (which makes hair) are turned on when they are on top of your head, but are turned off on the palms of your hands.