BOOK REVIEW / SCIENCE : Nature’s Designs Demonstrate Flexibility : THE SAND DOLLAR AND THE SLIDE RULE: Drawing Blueprints From Nature, <i> by Delta Willis</i> ,Addison Wesley, $23, 234 pages

If you hold a piece of paper in an outstretched hand and let go of it, the paper will fall slowly to the floor, moving this way and that as it goes.

Though the laws of physics that govern its descent are perfectly known, there isn’t a physicist on Earth who can predict with certainty exactly where the paper will land. If you do this several times, the paper will always come to rest in a different spot.

This simple experiment demonstrates one of the conundrums of modern science: In complex systems, the behavior of the whole is not predictable from knowledge of the parts. This is especially true of living organisms, an insight that is one of the themes of Delta Willis’ book “The Sand Dollar and the Slide Rule.” Living things are dynamic.

They are also very flexible. They grow and change, unlike, say, buildings or bridges. “Human inventions tend to be rigid and heavy,” Willis writes. “Plant and animal materials are generally lightweight and elastic.”

What’s more, over the eons of evolution, living things have become extremely efficient, using a minimum of materials to achieve a maximum of results. So, for example, we learn from this book that the tensile strength of a spider web, by weight, “is five times stronger than steel. A single strand of a spider’s silk could stretch 50 miles before breaking under its own weight.”

Besides being efficient, the principle of achieving a lot with a little turns out to have great aesthetic appeal. Consider the Eiffel Tower. It stands nearly 1,000 feet tall, but if it were melted down and spread out over an area the size of its base, it would form a sheet of iron just two inches thick.

Nature is extremely clever. Recognizing this, some human designers and engineers have sought to learn how nature does things and mimic the techniques. This is Willis’ central theme, which she explores with great sympathy and verve.

For example, the remarkable strength of spider silk has not gone unnoticed. Several chemical and biotechnology companies are studying the structure of the silk in hopes of creating synthetic fibers with similar properties.

But this approach is far from new. Leonardo da Vinci designed aircraft with flapping wings. They were not successful. But, Willis writes, “The Wright Brothers eyeballed turkey vultures to solve a key problem of lateral control, and Paul MacCready made some quick calculations for the Gossamer Condor [the human-powered aircraft] after sighting a couple of soaring birds.”

The book is chock-a-block with examples of nature’s amazing solutions to problems of design, interspersed with profiles of several engineers and thinkers who have adopted this idea, applied it and taught it.

Willis also devotes a chapter to Buckminster Fuller, who applied many of these ideas to his work. His most famous invention, the geodesic dome, is extremely lightweight, cheap and portable. But it is also very strong and can be built very large.

Despite the appeal of many of these ideas, it is fair to say that they do not represent the mainstream of engineering. People who pursue this work tend to be on the fringes of their professions, viewed as romantic dreamers at best.

Why is that? Willis never quite engages that question head on. Perhaps that’s not her task.

But if this work is as powerful as she claims, why has it not been taken up by more working professionals?

Is it just the inherent conservatism and inertia of all professions? After all, people who do things differently are in grave professional danger. “You get along by going along” is still good advice. Could be.

In any event, Willis lays out a different approach.