The Permian-Triassic extinction is an extinction that has been more devastating than the one that occurred at the end of the Cretaceous period. The extinction at the end of the Cretaceous managed to wipe out around 75% of the species on Earth, while the one at the end of the Permian managed to wipe out between 90 and 96% of the species. It is interesting for these two extinctions, that one lineage manage to survive through both of them, to late became the dominant one on Earth. At the end of the Permian the majority of the species died out, but several species of small sinapsids survived. The reptilians managed to evolve quicker, and the dinosaurs became the dominant lineage, but at the end of the Cretaceous they died out. The small sinapisids that managed to survive gave rise to the mammals, which survived in the shadows of the more dominant species, and after the second extinction managed to become the dominant lineage on the planet.
Na/K concentration in and out of the cell at the homeostatic level. It does this by pumping sodium and potassium ions in and out when it's needed of it in order to maintain the concentration of both ions stable across time.
