Levels of Organization in Biology and Ecology

This example illustrates the complexity of identifying toxic effects in nature. However, as with a human, there are built-in repair mechanisms that can overcome minor perturbations. Just as DNA can repair itself before cancer develops, effects to a few individuals, a population, or even a community can be corrected over a brief time period. It is only when the chemical exposure and toxicity overwhelm these repair mechanisms that permanent injury occurs. 

For example, the DDT story ends nicely in that, some twenty-five years after the ban on DDT, the peregrine falcon population has recovered to the point where it is no longer on the endangered species list. Since the banning of DDT, reproductive success has increased and the numbers of birds have recovered. If we had not banned DDT, these magnificent birds, unable to reproduce, might have become extinct. This illustrates the dynamic nature of our environment and its ability to heal itself if the cause of the problem is eliminated. 

As you can see, the environment can act as an interactive organism encompassing many species, including humans. Battles similar to those fought internally in our bodies cu e fought on a larger scale by ecological communities. 

Klaasen, C. D. (ed.). 1996. Casarett and Doull s Toxicology The Basic Science of Poisons, 5th ed. New York McGraw-Hill. 

Many of the toxicology tests discussed in this chapter are required under certain environmental laws, including the following U.S. acts  

---

Figure 4.1. Different Levels of Organization in Biology and Ecology...

---