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Environmental+Toxicology+Tox+2000+notes (2)

Thus in the ecosystem some organisms ecosystem after

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Unformatted text preview: ies in the sense that humans do. Thus, in the ecosystem, some organisms Ecosystem after impact may have a distinct function that reduced function and reduced diversity cannot be carried out by others (keystone organisms), whereas other may have their function replaced by Figure 3-11 another ―species‖ that can also The concept of toxic impacts on ecosystems perform the same function (redundancy). Conversely, species that appear to be morphologically similar (the most common way humans classify species) may perform different functions. An extreme case of this is where the same species may perform two roles such as the Arctic char ( Salvelinus alpinus) in Lake Hazen in the Arctic ( Reist et al. 1995). One of the problems in assessing Very stable effects in the ecosystem is that, ecosystem with many indicators of effect, like the rapid return to human pulse, are erratic. The normal observer must be able to distinguish Very unstable ecosystem the effects of love's lust from an impending myocardial infarction. What is very hel pful in this task is Multistable the ecosystem equivalent of a ecosystem with Bistable medical history, a difficult several endpoints at ecosystem with commodity to come by in a science different levels of two possible as young as complexity endpoints environmental toxicology. Most environmental records only go back a few hundred years at the most before they become cloaked in the veil of legend and folk -lore. There Figure 3-22 are some archaeological records Diagrammatic representation of ecosystems showing various forms of that can be used. The sediments in stability lakes can provide evidence o f historical events that relate to acidification or changes in human activities such as the combustion of wood and, more lately, release of persistent synthetic chemicals. The environmental toxicologist must take this into consideration in assessing impact s of toxic substances in the environment. It is now generally accepted that a significant environmental impact occurs when the structure and/or function of the ecosystem is permanently displaced from the normal as is illustrated diagrammatically in Figure 3-1. This displacement may be of a short-term nature and may be followed by complete recovery. On the other hand, recovery may occur but this may be to a different ecosystem, one that is permanently displaced, with a less diverse or functional norm. Ecosystems differ in their inherent stability as is illustrated in Figure 3-2. 3.1.3 Restoration of ecosystems One of the problems that will face us in the future is the restoration of ecosystems. As in the analogy to medicine, it is necessary to critically assess the effect of treatments before recommending a particular course of action. Medicine has only just b ecome able to properly judge its own treatments. History shows us that the many treatments such as blood -letting, leeches, magic, and other malarkey were totally useless as treatments and often made the patient worse, if not killing them. The ability to understand the cause of the disease and an understanding of physiology and biochemistry of humans has allowed modern medical treatments to...
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