The difference would be that impervious structures and surfaces generally do not allow molecules and compound to be transferred across. It is generally impossible to get something through an impervious surface. This isn't true, however, for pervious surfaces.
Herons are very large birds, and due to their intimidating size, they have very little predators. They have a varied diet and consume many different prey (fish, snakes, amphibians, and probably many other small animals). If the population of herons would decrease, the population of the other organisms living in the same environment would increase since they would have a greater chance at survival (since they are not being eaten by the herons)
D. A pond has 12 species of organisms including 300 animals and 40 plants
