Which is the smallest taxonomic group that contains organisms of different species

Genus

The complete and correct hierarchy of taxonomic groups from largest to smallest are:
1) Domain
     1.1) Archaea  1.2) Bactera  1.3) Eukarya
2) Kingdom
     2.1) Animalia  2.2) Plantae  2.3) Fungi  2.4) Protista  2.5) Archaea  2.6) Bacteria
3) Phylum - has 35 phyla
4) Class 
5) Order
6) Family
7) Genus
8) Species