Write a 11 pages paper on questions concerning biology. Different species, just like strains within the different species, react variably to specific toxicants because of the differences that they have in their respective metabolism. Other factors like absorption and elimination also determine their reactions. Young animals have an underdeveloped system of the microsomal enzyme. This contributes to the compromise of the translocation and metabolism of xenobiotic agents. Species, health, and age cause differences in the capabilities to clear both the renal and the hepatic system along with the permeability of membranes. The amount needed by a xenobiotic agent for pathology to occur has a direct relationship with the weight of the body. With massive body weight, a relative increase in the toxicity of a compound occurs disproportionately. The rise in the level of toxicity takes place per unit of body mass. The surface area that the body has may have a relationship with the amount of the toxin. It is imperative to note that there does not exist any measurement parameter that applies to every situation (Singh, 2012, 233).

NOAEL means the highest possible chemical exposure determined through the performance of toxicity tests among other methods of determination, having no observable adverse effect such as the onset of sickness even in a situation where the taking of the chemical takes place every day for the years that an organism lives. In practice, rats, mice, or other animals used in the tests are forcibly exposed to a specific chemical for a specified duration. The test is undertaken several times over, with the level of the dosage varying every time the test is done. The highest level of the dose that does not cause any adverse in the performed tests is taken as NOAEL. NOAEL stands for No Observed Adverse Effect Level. In usual cases, NOAEL can be expressed in the quantity of a specific chemical taken every day per kilogram body weight. for example, it may be expressed in Kg or mg per day (Remic, 2012, 148).&nbsp. &nbsp.&nbsp.