The extreme challenges of life in the polar regions require the animals who make their habitat there to make many adaptations. This unit explores the polar climate and how animals like reindeer, polar bears, penguins, sea life and even humans manage to survive there. It looks at the adaptations to physiological proceses, the environmental effects on diet, activity and fecundity, and contrasts the strategies of aquatic and land-based animals in surviving in this extreme habitat. This unit builds on and develops ideas from two other 'Animals at the extreme' units: The desert environment (S324_1) and Hibernation and torpor (S324_2). This study unit is just one of many that can be found on LearningSpace, part of OpenLearn, a collection of open educational resources from The Open University. Published in ePub 2.0.1 format, some feature such as audio, video and linked PDF are not supported by all ePub readers.