Kingdom; phylum; class; order; family; species; genus
The reason why crack is more addictive than cocaine was
because it is smokable of which cocaine could not do and by smoking it, it
easily reaches the brain—making a person addicted to it than the cocaine in
which is not even smokable.
I'm not sure if I will answer the question you asked, as I many have interpreted it incorrectly. In natural selection, there must be variance in the gene pool, the total frequency of alleles in a population. Now, one of the organisms may have a gene that somehow helps them survive from the selective force much better compared to the others. If this does happen, over time the gene pool will narrow down to become just the genes of that organism that survived better in the first place because the rest would be taken care of by the selective force. So, the alleles and trait come from the first organisms that had the advantage over the others of its species.
