The terrestrial and native year-round species appear to be the descendants of ancestors who lived in geothermally warmed environments during the last ice age when these areas were the only places on the continent not covered by ice.

Animals

Antarctic krill, which congregate in large schools, is the keystone species of the ecosystem of the Southern Ocean, and is an important food organism for whales, seals, leopard seals, fur seals, squid, icefish, penguins, albatrosses and many other birds.

Few terrestrial vertebrates live in Antarctica, and those that do are limited to the sub-Antarctic islands.Some species of marine animals exist and rely, directly or indirectly, on the phytoplankton. Antarctic sea life includes penguins, blue whales, orcas, colossal squids and fur seals. The emperor penguin is the only penguin that breeds during the winter in Antarctica; it and the Adélie penguin breed farther south than any other penguin.The snow petrel is one of only three birds that breed exclusively in Antarctica. The Antarctic fur seal was very heavily hunted in the 18th and 19th centuries for its pelt by sealers from the United States and the United Kingdom.The Weddell seal, a “true seal”, is named after Sir James Weddell, commander of British sealing expeditions in the Weddell Sea. The leopard seal is an apex predator in the Antarctic ecosystem, and they migrate across the Southern Ocean in search for food.

Fungi

About 400 species of lichen-forming fungi are known to exist in Antarctica.

About 1,150 species of fungi have been recorded from Antarctica, of which about 750 are non-lichen-forming and 400 are lichen-forming.Some of these species are cryptoendoliths as a result of evolution under extreme conditions, and have significantly contributed to shaping the impressive rock formations of the McMurdo Dry Valleys and surrounding mountain ridges. The apparently simple morphology, scarcely differentiated structures, metabolic systems and enzymes still active at very low temperatures, and reduced life cycles shown by such fungi make them particularly suited to harsh environments such as the McMurdo Dry Valleys.

Plants

About 300 million years ago Permian forests started to cover the continent, and tundra vegetation survived as late as 15 million years ago,but the climate of present-day Antarctica does not allow extensive vegetation to form. A combination of freezing temperatures, poor soil quality, lack of moisture, and lack of sunlight inhibit plant growth. As a result, the diversity of plant life is very low and limited in distribution. The flora of the continent largely consists of bryophytes. There are about 100 species of mosses and 25 species of liverworts, but only three species of flowering plants, all of which are found in the Antarctic Peninsula: Deschampsia antarctica (Antarctic hair grass), Colobanthus quitensis (Antarctic pearlwort) and the non-native Poa annua (annual bluegrass). Growth is restricted to a few weeks in the summer.

Other organisms

Seven hundred species of algae exist, most of which are phytoplankton. Multicolored snow algae and diatoms are especially abundant in the coastal regions during the summer. Bacteria have been found living in the cold and dark as deep as 800 m (0.50 mi; 2,600 ft) under the ice.