The evolution of iguanas in the Galápagos provides a striking example of the workings of natural selection. This entry in the How Nature Works series explains how scientists have determined that two surprisingly different species evolved from a single ancestor. Collard's smoothly written text introduces two kinds of iguanas now living on these islands: a prickly pear-eating land iguana and a marine iguana that feeds on green algae underwater. He goes on to describe the volcanic origin of the archipelago and how plants and animals arrived. Drawing on well-grounded scientific conjecture (described in one of six informative sidebars), he then imagines the arrival of the first ctenosaur from Central America 8.25 million years ago and, after 3.75 million more years, the evolution of its algae-eating descendent. He introduces the theory of natural selection and, in another sidebar, explains how genes and their alleles contribute to individual differences. Returning to the continuing evolution of these two species, he shows how each has become perfectly adapted to its habitat. Finally he touches on other unique Galápagos inhabitants and the development of the theory of natural selection. A helpful map locates the Galápagos; images of its reptiles, birds, sea lions, and scenery will help readers picture the setting today. The attractive design makes good use of these well-reproduced photographs, some taken by the author.A fresh and accessible approach to an important scientific concept. (glossary, suggestions for further research, author's note) (Nonfiction. 9-13)

True to its name, the How Nature Works series (2 new titles) aims to explain elements of the natural world and how they function. That's an enormous topic, but a common thread of inviting writing and a critical-thinking focus tie these very different volumes nicely together. One Iguana, Two Iguanas takes a much more focused approach, discussing two wildly different species, marine iguanas and Galapagos land iguanas, and how they evolved from a common ancestor. Apart from profiling these creatures, this volume does an excellent job of illustrating evolution and natural selection with the concrete example of these two reptiles as well as explaining the ways scientists determine common genetic ancestry among species. Both volumes boast appealing layouts, accessible writing, and specific scientific terms, all of which are defined in a closing glossary. With higher-level vocabulary and concepts in an invitingly visual package, these slim volumes are perfect for students making their ways into more advanced nonfiction.

The Galapagos Islands are home to marine iguanas that, like no other iguana species, swim and feed in the ocean. Collard's story of how this came to be is an explanation of island biogeology, evolution, and natural selection in the locale that inspired Darwin. Crisp, detailed photographs of the animals, along with sidebars that provide deeper explanations of evolutionary biology, are included. Reading list. Glos.

The evolution of iguanas in the Galápagos provides a striking example of the workings of natural selection. This entry in the How Nature Works series explains how scientists have determined that two surprisingly different species evolved from a single ancestor. Collard's smoothly written text introduces two kinds of iguanas now living on these islands: a prickly pear-eating land iguana and a marine iguana that feeds on green algae underwater. He goes on to describe the volcanic origin of the archipelago and how plants and animals arrived. Drawing on well-grounded scientific conjecture (described in one of six informative sidebars), he then imagines the arrival of the first ctenosaur from Central America 8.25 million years ago and, after 3.75 million more years, the evolution of its algae-eating descendent. He introduces the theory of natural selection and, in another sidebar, explains how genes and their alleles contribute to individual differences. Returning to the continuing evolution of these two species, he shows how each has become perfectly adapted to its habitat. Finally he touches on other unique Galápagos inhabitants and the development of the theory of natural selection. A helpful map locates the Galápagos; images of its reptiles, birds, sea lions, and scenery will help readers picture the setting today. The attractive design makes good use of these well-reproduced photographs, some taken by the author.A fresh and accessible approach to an important scientific concept. (glossary, suggestions for further research, author's note) (Nonfiction. 9-13)

Gr 3-7 Collard relies on his trademark style in this latest title that demonstrates how a species evolves in response to its environment. The author compares two types of lizards found on the Galápagos Islands: one that dives underwater to eat ocean algae and another that eats prickly pears. Using the latest scientific theories to explain how a lizard ancestor could have reached the islands, Collard deftly examines why the two iguana species are so different in size, coloration, and other traits despite their common heritage. Detailed photographs illustrate the differences between the species and show other flora and fauna of the archipelago. Helpful sidebars discuss topics such as the use of DNA in dating the divergence of species, the giant tortoises of the Galápagos, and Charles Darwin's famous exploration of the area. Back matter includes suggested titles for further reading on evolution, Darwin, and the Galápagos. VERDICT A comprehensible explanation of evolution and adaptation, perfect for elementary and middle school collections. Suzanne Costner, Fairview Elementary School, Maryville, TN