Mechanism of action of toxicants varies from chemical to chemical. Some chemicals cause cytotoxicity, i.e., they act by causing cell death. A number of chemicals are able to cause genotoxicity, i.e. they are able to produce their effect by altering gene expression. Generally, toxicants produce their effects by interference with physiological or biochemical homeostatic (regulatory) mechanisms. Some of them can [...]
In the environment, the concentration, transport, transformation and fate of a chemical are affected by several factors. Factors which affect overall toxicity may be described under four headings; 1. Factors Related to Chemical: Physico-chemical properties: The physico-chemical properties of a compound that are considered important include its molecular structure, solubility, ionization and vapour pressure. All these characteristics affect the toxicological [...]
Each community has a variety of species, some of which are rare, others are common and still others are abundant. Thus, no community consists of species of equal abundance. Diversity tends to increase with increase in the area sampled, since the sampling progressively brings in a wider spectrum of habitats, ecosystems and biomes for consideration. The following types of species [...]