The term mammal encompasses a huge variety of animals, including humans. But what makes a mammal a mammal? This unit explores some of the features, such as reproduction, lactation and thermoregulation methods, that mammals have in common. To get the most out of this unit you will need access to a copy of The Life of Mammals (2002) by David Attenborough, BBC Books (ISBN 0563534230), and The Life of Mammals (2002) on DVD, which contains the associated series of BBC TV programmes. 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.