The+killing+chain

__ The Killing Chain  __

Biodegradable substances are those which can be broken down by microbes into harmless compounds. Non-biodegradable substances cannot. Therefore they build up in the soil or marine environment. They are known as conservative pollutants, and these, harm not only the environment but also all the species surrounding it. Examples of Conservative Pollutants include: Pesticides:



Heavy metals such as: Tin, lead and mercury:

Organisms may ingest or absorb a pollutant, or even more than one at a time. This produces a toxic effect. Different organisms show varying degrees of sensitivity to toxins and this sensitivity may depend on age, sex, food availability, reproductive condition and genetic make-up. Consider the following story:



This story explains how toxins get into the food chain. Starting from the primary consumer which was the worm and passing through the next trophic level to the tertiary consumer which is the hawk. In the change from each trophic level, the toxins will bioaccumulate in the tissues of each consumer. Bioaccumulation takes place because as you go up the pyramid of numbers, the number of individuals at each trophic level tend to decrease and to be bigger, while the individuals on the lower trophic levels tend to increase and get smaller. Therefore the individuals on the top trophic levels eat more as they are larger and need to eat more to get enough energy to survive. Biomagnification occurs in here because the organisms in the top trophic level eat more so contain more pesticide in their tissues. This spots the top carnivores in a very vulnerable position, as they are the most affected from this whole process as they have to eat more.