Species

In Tetrian Biology, a species is defined as a group of organisms in which more than one third of its genome is unique to that group. This differs greatly from the definition of a species used on Earth which is based on the ability to produce fertile offspring. The decision by Tetrian biologists to classify species based on an arbitrary threshold of genetic similarity was necessitated by the fact that most randomly selected pairs of the same species are unable to reproduce at all due to enormous variation between individuals. While large sample sizes of Tetrian organisms show a strong correlation between genetic similarity and fertility, there are so many outliers that a statistically sound conclusion cannot be drawn about whether any two specific individuals represent the same species based on fertility alone.

Tetro is home to 25 species of living organism, shown with their classification in the chart below.