An extremophile is an organism that lives in an extreme environment. An extreme environment is one in which most organisms would find it difficult or impossible to survive. The organisms that live in these places have highly specialised adaptations. Examples of extreme environments include the Polar Regions, deserts, the deep ocean bed, hot geothermal springs and the tops of our highest mountains.
The North Pole is called the Arctic and contains polar bears. The South Pole is the Antarctic. It has no polar bears, but many penguins. Both the Arctic and Antarctic are extremely cold, often averaging -40°C. In the Northern hemisphere summer the North Pole has has 24 hours of daylight and the South Pole experiences 24 hours of night. This is then reveresed during the Northern hempisphere winter.
Animals, like polar bears, at the North Pole are adapted to suit these conditions. They have thick white fur for insulation and camouflage. They have acute senses of smell and sight to hunt prey. They have small surface area : volume ratio to minimise heat loss and a thick layer of fat to keep warm.
Penguins at the South Pole have many of the same adaptations. In addition, the male Emperor penguins have evolved to insulate their egg on their feet throughout winter. This is a behavioural adaptation.
Deep sea volcanic vents are places on the ocean floor where the volcanic gases of underground magma chambers bubble through. These form plumes of gases which are very hot. These are extreme environments because of this heat and the high pressure that comes at the bottom of the ocean. They are utterly dark.
Here, bacteria feed on the chemicals released from the volcanic vents. Worms feed on the bacteria, and then other species feed on the worms. Until the recent discovery of these ecosystems we thought all food chains and webs started with photosynthesising plants or algae. The producers here are bacteria that feed on chemicals. These ecosystems are therefore unique on Earth.
Because of the extreme environment at the bottom of the oceans organisms find it difficult or impossible to move from one vent to another. This has resulted in many hydrothermal vents having separately evolved species that are only found in this one location. The adaptations of these animals allows them to survive in these conditions.