Here's why:
* Species: A species is a group of organisms that can interbreed and produce fertile offspring. This is the most specific level of classification.
* Genus: A genus contains multiple related species.
* Family: A family contains multiple related genera.
* Order: An order contains multiple related families.
* Class: A class contains multiple related orders.
* Phylum: A phylum contains multiple related classes.
* Kingdom: A kingdom contains multiple related phyla.
* Domain: The broadest level of classification, containing multiple kingdoms.
As you move up the hierarchy from species to domain, the number of organisms included in each level increases.
