The smallest systematic group is?

Biological taxonomy studies all living nature and groups living organisms according to various similarities. These can be anatomical, morphological, and other common features. The largest systematic group is life. It unites all living things. The smallest taxonomic rank is species. There are tens of millions of species on our planet. The exact number of species will never be counted, since we cannot study our entire planet. In the oceans, unexplored plants, animals and bacteria remain. Therefore, we can only name an approximate number of species.