Why do species included in a genus resemble in many features

A group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding. The species is the principal natural taxonomic unit, ranking below a genus ,which means let us assume we have 10 organism in a particular genus so out of tht 10 organisms if 2 are have such a resemblance of charaterstics that they can even reproduce to form a fertile offspring than those two organisms will be put into same species,t hus even if the other 8 organisms form species do not have a very close proximity of characters to reproduce wth each other,but in general they hav high amount of silarity and resembla ce in characters ,PLEASE HIT LIKE !!!!