The term speciation is basically the origin of a new species. Sympatric speciation and Allopatric speciation are the 2 major mechanisms of speciation
when a population of organisms is isolated from their main group is allopathic speciation. It can isolated for various reasons like change in landscape and other.
Sympatric speciation takes place in a population without any geographic isolation but involves changes in the chromosomes set of the organism
Nicotine, once in the brain, will work specifically on nicotinic receptors in the brain. However, there is a common "addiction" pathway in the brain that pretty much all addictive substances go through.
