“BIOLOGICAL DARK MATTER, akin to cosmological dark matter, is an apt descriptor for this overwhelming and unseen component of the biosphere. These studies are forcing us to recognize that, rather than typifying life, multi-cellular eukaryotes are actually a derived and highly constrained evolutionary subset of the biosphere.”
https://standardsingenomics.biomedcentral.com/articles/10.1186/s40793-016-0180-8