There are 35 sub-species of Barn Owl. Barn Owls do not build nests themselves, but rely on a variety of nesting sites for laying their eggs. Tree cavities, rock ledges, chimneys & ledges in barns are among the sites that may be used & Barn Owls have sometimes been known to make their own burrows in riverbanks.
Organisms in biology are classified by this system: kingdom, phylum, class, order, genus, species. Kingdoms being the largest groups. Species is the smallest major group before they divide into sub groups. So Genus would be the next group larger if that is what you mean, but all the other groups would be larger as well.
After a deep study of Monera kingdom characteristics, the kingdom was divided into two groups Archaea and Bacteria. This classification of living things was under the three domain system of taxonomy that was established in 1991. The third domain included the Eukaryote group.