Population density over time:
![](http://wordpress.up.edu/envscitheobook/files/2011/08/Screen-Shot-2012-04-10-at-6.40.14-PM.png)
Because of developments over time, human population has radically increased as time goes on and lifespans lengthen.
Carrying capacity of ecosystems:
![](http://wordpress.up.edu/envscitheobook/files/2011/08/carrying.jpg)
Historically, whenever any population goes over carrying capacity, that population will follow its increase with a dramatic decrease. Like a cycle, the carrying capacity of ecosystems determines its population and circulates its stages over time.
Overshoot:
![](https://sites.up.edu/envscitheobook/wp-content/uploads/sites/128/2011/08/Overshoot_21.jpg)
If population density rises so suddenly that it overshoots the carrying capacity of the resources on which it depends, an overshoot can occur and carrying capacity can be degraded to a lower level.