Domains and Kingdoms

Domains

Life on Xenosulia is divided into three main branches, with the taxonomic rank of domain. 

Xenosulibacteria

Xenosulibacteria are simple organisms, similar to the bacteria or archaea of Earth. It is likely that this group is paraphyletic, being ancestral to the other two domains. 

Rytocaryota

Rytocaryotes are far more complex, with the vast majority of macroscopic organisms fitting into this domain. They are usually seen as the Xenosulian equivalent of eucaryotes, although there are a number of differences. Firstly, they lack mitochondria, with the role being assumed by a wrinkled structure around the nucleus. The cell is also divided into an inner and outer section, separated by a cellular membrane similar in structure to the membrane on the outside of the cell; most organelles are on the outer section, and the outer section has its own genes but lacks a nucleus. The vast majority of genetic information is stored in the inner cell’s nucleus. 

Allocaryota

This group has cells as complex as those of rytocaryotes, although different enough that it’s obvious they developed independently. Genetic evidence confirms this. This domain includes multicellular organisms, most notably the plant-like allophytes, although rytocaryotes are far more common.

Kingdoms

There are four main rytocaryote kingdoms, although there are many simple organisms that don’t fit into any of these groups. Still, most large multi-celled life belongs to one of these kingdoms. 

Xenosuliphyta

This kingdom comprises the majority of the planet’s plantlife; the term “plant” being expanded to include photosynthesising life outside of the kingdom Plantae. Like the plants on Earth, they use carbon dioxide as a carbon source, something that has proven to be far from universal (with methane being a common alternative; in fact, many allocaryotes do use methane, and generate most of the hydrogen present in the atmosphere), although many plants do also use carbon monoxide too. Xenosuliphytes are responsible for much of the planet’s oxygen, with allophytes and chemotrophians also contributing. They possess cell walls, often composed of various different sugars, although the cell walls can also be mineralised. 

Xenosulizoa

These organisms don’t photosynthesise, and many can be quite active. They are very similar to the animals of Earth, and are referred to as such. Differences from Earth animals include the presence of cell walls, which can be composed of various different proteins and, like xenosuliphytes, may be mineralised. However, in more active groups the cell walls of many tissues may be greatly reduced or absent. 

Chemotrophia

As the name suggests chemotrophians are chemotrophic organisms, which along with xenosuliphytes act as primary producers. They are especially common on the planet’s dark side where photosynthesis is more difficult, using the methane, hydrogen sulphide and hydrogen present in the atmosphere as a source of energy. 

Kinetotrophia

Members of this kingdom gain energy from motion, changes in heat, and receiving impact forces. Wind is a large source of energy, although the movement of animals also contributes. They are especially common on the planet’s night side where they face little competition for nutrients from plants.