Cycles of Nature: An Introduction to Biological Rhythms by Andrew Ahlgren and Franz Halberg
	(Illus.) National Science Teachers Association 1990 viii+87pp. 0-87355089-7 JH-T, GA *

Secondary school students who wish to do a science fair project related to the effects of biorhythms are frequently frustrated in their search for literature on the topic that is written at a level they can understand. This book provides a source of knowledge written in a manner understandable by the layperson. Its introduction and seven chapters introduce chronobiology and discuss the central ideas of the field. The book can provide teachers with materials for a one- to two-week unit on this topic, suitable for use in secondary science classes. Experiments are discussed throughout the chapters, and chapter seven provides details for conducting eight experiments. The materials needed are commonly available: the students themselves, a small animal such as a mouse or hamster, and bean seeds. The eighth activity poses some safety hazards and is designated as a teacher demonstration. The authors, one a science educator and the other a professor of laboratory medicine who also directs the University of Minnesota's Chronobiology Laboratories, have produced a book that should be of interest to readers from middle school to adults. They write clearly, have kept the technical jargon to a minimum, and have illustrated their points with charts, graphs, and diagrams. Also helpful are side comments, printed in bold-face type, on the margins of certain pages. These are designed to reinforce the information presented or to expand on it. Study questions designed for students to apply the given information to real-life situations are found at the end of each of the first six chapters. A 28-item bibliography concludes the book.

--Reviewed by Patricia E. Blosser in Science Books and Films, 27/1 (January 1991), p. 9.