Paperback. Pub Date :2013-04-01 Pages: 40 Language: English Publisher: Kids Can Press If every known species on Earth were a leaf on a tree. that tree would have 1 750 000 leaves. Since humans count for just one leaf on the tree. we have a lot to learn about the millions of other forms of life with which we share the world. A dazzlingly illustrated and child-friendly introduction to biodiversity. Tree of Life shows how living things are classified into five kingdoms - and how each has much to tell us about all aspects of life on our planet. Tree of Life is part of CitizenKid: A collection of books that inform children about the world and inspire them to be better global citizens.