What are pesticides and herbicides? Explain giving examples.

Explanation

Pesticides are synthetic chemicals used for destroying pests. These are used to kill or destroy unwanted dangerous species of plants and animals. These are basically synthetic toxic chemicals with ecological repercursions. The repeated use of the same or similar pesticides make some pests resistant to that group of pesticides, thereby, making the pesticides uneffective. For example, when insect resistance of DDT increased, other organic toxines such as Aldrin and Dieldrin, etc., were introduced. Most of the organic toxins are water insoluble and non-biodegradable. Therefore, these high persistent toxins are transferred from lower trophic level to higher trophic level through food chain. Over the time, the concentration of toxins in higher animals reach a level which causes serious metabolic and physiological disorders. Herbicides are used to kill weeds or undesirable vegetations. For example, sodium chlorate `(NaClO_(3))`, sodium arsenate `(NaAsO_3)`, 2, 4 dichlorophenoxy acid, triazines, etc.