What makes a frog an amphibian but a snake a reptile? Both classes may lay eggs, but they have different skin coverings and breathe in different ways. Pages of

"Ambrose, a polar bear, and Zina, a penguin, are very different but they can still find ways to meet in the middle."--

When Pierre, an African penguin living at the California Academy of Sciences, begins to lose his feathers, the zoo staff is at a loss as to what to do. The lack

"All mammals share certain characteristics that set them apart from animal classes. But some mammals live on land and other mammals spend their lives in water--

Compares and contrasts the features of different types of trees.