Here's why:
* Domain: The highest and most inclusive level of classification in the current system. It encompasses all of life. The three domains are Bacteria, Archaea, and Eukarya. Organisms in different domains are incredibly diverse and have fundamental differences in cellular structure, genetics, and biochemistry.
* Kingdom: The next level below domain, grouping organisms with similar characteristics. Examples include animals, plants, fungi, and protists. Organisms in different kingdoms are still quite different.
* Phylum: A group of closely related classes.
* Class: A group of closely related orders.
* Order: A group of closely related families.
* Family: A group of closely related genera.
* Genus: A group of closely related species.
* Species: A group of organisms that can interbreed and produce fertile offspring.
As you move from domains down to species, the organisms within each group become more and more similar.
