The first line of defence (or outside defence system) includes physical and chemical barriers that are always ready and prepared to defend the body from infection. These include your skin, tears, mucus, cilia, stomach acid, urine flow, 'friendly' bacteria and white blood cells called neutrophils.
Receptors detect changes in the environment. For a stimulus to elicit a response, certain cells must have an appropriate receptor. Stimulation of the receptor initiates a specific signal pathway.
The human body strives to maintain homeostasis, the state of balance between internal and external change.
The generic name of poisonous chemicals, very often used in commercial agriculture that are used to kill organisms that either reduce the yield of crops or are harmful to animals are pesticides.
Pesticides are the chemicals used to kill the pests affecting the growth and yield of the crops. Pesticide is a broad term covering various small terms according to the pest being killed. For example insecticide, nematicide, avicide, rodenticide, bactericide, etc. Some chemicals used as pesticides are boric acid, Acephate, Deet, Propoxur, glyphosate, etc.
Commercial agriculture means growing of crops so as to sell them in the market to be utilized by the wide population of any area. Any crop can be grown at the commercial level. These crops do not reach the customers directly by the farmers, instead they are sold to whole-sellers first.
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