Book excerpt: Keeping warm in subzero temperatures can be difficult. Some animals can't manage to retain their body heat in cold weather. However, some animals such as the muskox have adapted to survive in cold climates. They have long, shaggy fur that keeps them warm in the colder months, which they shed in the summer months to stay cool. Other animals such as bears and seals have a layer of fat to keep them warm. The information in this book highlights how these adaptations have developed over many thousands of years. The information in this book supports essential elementary life science concepts.