FIGURE 5.10 Negative and positive feedback loops. (a) A negative feedback loop occurs at Mono Lake: When the water level drops, the lake surface area is reduced and evaporation decreases. As a result of the decrease in evaporation, the lake level rises again. (b) Population growth is an example of positive feedback. As members of a species reproduce, they create more offspring that will be able to reproduce in turn, creating a cycle that increases the population size. The green arrow indicates the starting point of each cycle.