Taxonomic Classification: From Domain to Species
In biology, we categorize life by how similar they are to each other.
Each level of classification answers a general question about the species.
Like a family tree, we can see the relationship for any living organism by observing the following classification of life.
Let’s dive into the 7 taxonomic classifications of life on Earth.
“Domains” are the top-level classification which categorizes life in the most general way. It’s even more general than asking whether an organism is a plant or an animal.
For example, protists, fungi, plants and animals are part of the eukarya domain. This is because their cells all have a nucleus. While prokaryotes like archaea and bacteria don’t have one, eukarya have a nucleus. So the 3 domains of life are archaea, bacteria and eukarya.
The other two kingdoms are eubacteria and archaebacteria which do not have a cell nucleus. These single-celled microorganisms evolved in the early stages of Earth’s formation and have a very different cell anatomy from eukarya.
After domains, the kingdom classification gets a bit more specific.
For example, is it a plant or animal? If it’s a plant, we categorize it in the plant kingdom. If it’s an animal, it’s part of the animal kingdom.
The 7 kingdoms of biology are: bacteria, archaea, protozoa, chromista, plantae, fungi and animalia.
As we move down the levels of the classification of life, kingdoms are below domains. Each phylum is grouped into a kingdom, which is grouped into a domain.
The animal kingdom contains approximately 35 phyla. Next, the plant kingdom consists of 14. Finally, the fungus kingdom contains 8 phyla.
Humans are part of the animal kingdom taxonomy. Next, we belong to the chordata phylum which have these four common characteristics: a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail.
Another example from the animal kingdom is the arthropoda phylum which are invertebrates animal with exoskeletons. For example, all insects, spiders, crustaceans belong to this phylum.
As you move through the levels, the questions get more specific. Each order has a class, which is grouped into a phylum.
For the animal kingdom, there are 35 phyla. Then, these phyla can be broken up into 107 classes.
For example, the chordata phylum contains mammals, reptiles and amphibians.
After, we group orders into classes. And in the taxonomy classification below, genus can be grouped into orders.
If you look at the human taxonomy, our class is mammalia. Then, our order is primates.
Orders have a separate sub-division called a family. For example, humans are part of the Hominidae family.
Each genus has a family. They also belong to a species, which is the most specific taxonomic classification of them all.
For example, our genus is homo. Gorilla is a genus. It has two species which are the western gorilla and eastern gorilla.
When you hear a scientific name, it uses the genus and species.
The taxonomic classification of “species” is the most specific you can get.
Each species belongs to a genus. Then, it goes down the chain of taxonomic classification into an order, class, phylum, kingdom and domain.
Biologists have identified approximately 1.3 million species on Earth. But it is estimated that 8.7 million species can exist on the planet.
The animal kingdom is the largest with approximately 1 million species. Then, the plant kingdom is second largest with approximately 250,000 different species.