The lowest unit of classification is the species.
In biology, species is the basic unit of classification and the most specific level of classification in the hierarchical classification system. A species is defined as a group of living organisms that are capable of interbreeding and producing fertile offspring. This means that members of the same species can mate and have babies that can also reproduce. The species is the smallest unit of classification in the biological system, and all living organisms can be classified into a species based on their shared characteristics and genetic makeup.
Above the species level, organisms are classified into higher levels such as genus, family, order, class, phylum, kingdom, and domain, based on their similarities and evolutionary relationships. These higher levels of classification group species into larger and more inclusive categories, allowing us to understand the relationships between different types of organisms and the diversity of life on Earth.