We are very fortunate to be living in a wonderful age of progress. The rapid march of science today borders on the revolutionary. It will not be necessary for future historians to look back at our era and designate it as a period of great change for we can see these advances taking place before our very eyes on an almost day-to-day basis, and we are aware that they are the most exciting that mankind has ever experienced. The marvels of atomic energy already have been superseded in our imaginations by the breathtaking vistas of the space age. Artificial planets orbiting around the sun, space ships with astronauts revolving about the earth, and rockets arriving at the moon make it quite clear that travel to our nearest neighbors in the solar system - the moon, Mars, and Venus - will almost certainly be accomplished within a decade. We are passing a boundary of history and all of us already have an inkling of the momentous character of the breakthrough.

But what has all this to do with biology? The answer - a revolution of similar proportions, and no less exciting, has been occurring in the biological sciences and at an ever-accelerating pace. It has been brought to the attention of the general public to a limited extent by such spectacular medical accomplishments as antibiotics, polio vaccine, and open heart

surgery, to name but a few. But far greater and more fundamental conquests have been quietly and inexorably taking place, unaccompanied by the blare of publicity, paving the way for these invaluable applications of pure research. Consider, for example, the formulation and documentation more than a century ago of two fundamental concepts in biology: the cell theory and the Darwinian theory of evolution. The latter with certain modiflcations has since emerged as one of the most important unifying principles in biology.

Modern biology can no longer be regarded as a collection of descriptive information of living forms. Broad principles have been emerging and crystallizing from the vast compilation of biological facts, reflecting the shift in emphasis from the descriptive to the experimental and the interpretive. The modern biologist no longer is occupied chiefly with "what is this." He now concentrates more than ever on the "hows" and "whys."

In virtually all areas there has been a marked tendency to analyze biological phenomena in terms of the laws of chemistry and physics. The remarkably successful application of biochemistry and biophysics has been most striking in the fields of metabolism, genetics, and evolution. In genetics, for example, the last two decades have witnessed a growing interest in the mechanism of gene action rather than in the mechanics of heredity alone. As a result the behavior of the gene has been increasingly related to its physical and chemical nature. This has revealed, among other things, the close relationship between genes and somewhat similar particles, the viruses. In turn the mechanism of evolution is being examined increasingly in the light of metabolic and genetic changes at the molecular level.

These concepts, together with the interpretation of cellular activities in terms of biochemical reactions and concomitant energy relationships, have led to the projection of reasonable theories, based on purely scientific criteria, regarding the origin of life on the planet earth and its evolution to present-day forms. The discoveries of modern biochemistry and biophysics have had an impact on all areas of biology including cytology, embryology, taxonomy, immunology, physiology, and evolution. These are the facts of life !

This book, in presenting a course in modern biology, of necessity seeks to include an evaluation of many biological phenomena in biochemical terms. It is also essential, however, to include the broad concepts of classic descriptive biology. It would be an incomplete treatment to favor one phase to the exclusion of the other. The guiding concept has been to expose the student to the broad principles of modern biology from both the molecular and classically descriptive views with the ultimate aim of demonstrating the intimate relationship between the two. The main objectives are to analyze critically the structural and functional features of living things (and their interrelationships) from various aspects ranging from the molecular level to the whole organism. In all cases the major emphasis will be to examine the broad unifying principles of biology, as we know them today, and the detailed facts and information from which they are derived. The areas of biological ignorance as well as knowledge will be indicated.

The book has been written for both one-semester and two-semester introductory courses in undergraduate biology, with a decided effort to omit technical nomenclature wherever feasible. It does not presuppose a previous knowledge of chemistry, and, in fact, hopes to fill this gap as far as some of the basic principles of chemistry and biochemistry are concerned. In order to give the student an appreciation of the biochemical influence in biology, a number of optional chapters have been devoted to a broad and comprehensive treatment of chemical and biochemical principles, more so than is usually found in biology textbooks. A decided effort has been made to present these chemical and physical concepts along lines that allow the student to visualize their meaning and signiflcance when applied to biological phenomena. It has been my experience that students lacking a formal background in chemistry find themselves at a distinct disadvantage in an up-to-date introductory college biology course. Their efforts to gain this background on their own by referring to chemistry textbooks are usually unrewarding. For those students who have been exposed to some formal course work in chemistry, it is hoped that the chapters on chemistry and biochemistry will serve not only as a helpful review but also as a suitable orientation for the biology that follows in the main body of the book.

It should be pointed out, however, that the design of the book is such that the presentation of the biological material does not depend on the preceding chemistry and biochemistry chapters. Whether or not these chapters are used is left to the discretion of the instructor and student. The chemical and biochemical material may be omitted or utilized, depending on the level at which the course is being given. Aithough these chapters will aid in understanding many biological phenomena, they are not absolutely essential for the utilization of the book.

The attempt has been made to integrate the biochemical aspects of various biological phenomena and the classical descriptive views with the appropriate subject matter. Wherever feasible brief narrations of some of the experiments that led to momentous discoveries have also been incorporated. These narrations are intended to illustrate the significant

roles played by the scientific method, original and often unorthodox ideas, keen observation, and, sometimes, sheer good luck. In addition, the application of basic discoveries to practice has been indicated. Finally, an effort has been made during the presentation of subject material to point out the unsolved problems and controversial areas in biology with a view to stimulating the student.

In addition to the more extensive treatment of the basic relevant chemical and biochemical concepts, a number of other departures have been made from the format common to most introductory biology textbooks. Two early chapters are devoted to a broad nontechnical description of the concepts of the origin and evolution of the universe for both inanimate and living components. The primary motivations were, first, to offer an overall view of the setting and relationship of life in the immense background of the universe, and, second, to illustrate in general terms the operation of the fundamental principles of evolution not only in biology but in the inanimate world (e.g., astronomy, geology) as well. This seemed especially worthwhile before considering the detailed aspects of biology in the chapters that follow. Various phases of the origin and evolution of living things are treated again in the later chapters, but in greater detail with the accent on genetic and biochemical aspects.

Another departure has been to handle the chapters on heredity and genetics, usually reserved for the latter portion of most textbooks, as basic subject material by presenting them immediately after the sections on cell structure, cell physiology, and biochemistry.

For several reasons emphasis has been placed on the human body. Biological phenomena, especially when abstract concepts are involved, have considerably more meaning (and interest) for the beginning student when presented in reference to Homo sapiens. This approach in addition fills an unexpectedly large gap in the student's background of general information by providing him with knowledge about human anatomy and physiology of which he often knows surprisingly little.

Judging from my experience in teaching this course to science and nonscience students at The Johns Hopkins University during the past fourteen years, the response to this approach has been most gratifying. It has aroused interest and curiosity and, most of all, it has imparted to the student a picture of modern biology as we know it today.

I am grateful for the expert advice of Dr. Howard A. Bern who read and critized the manuscript in its entirety, and to the following persons for their suggestions and criticisms of various chapters: Dr. Maurice J. Bessman, Dr. David Bodian, Dr. John W. Gryder, Dr. William .F. Harrington, Dr. Philip E. Hartman, Dr. Thomas R. Hendrix, Dr. Andre T. Jagendorf, Dr. Julius R. Krevans, Dr. Martin G. Larrabee, Dr. Joseph D. Lichtenberg, Dr. Edward F. MacNichol, Jr., Dr. Clement L. Markert, Dr. William M. Mitchell, Dr. Alex Nickon, Dr. Alex B. NovikofF, Dr. Abraham G. Osler, Dr. Solbert Permutt, Dr. David Rabinowitz, Dr. Howard L. Sanders, Dr. Howard H. Seliger, Dr. William L. Straus, Jr., Dr. Sigmund R. Suskind, Dr. Rowland W. Taylor, Dr. Harry A. Teitelbaum, Dr. W. Gordon Walker, Dr. Theodore R. F. Wright, Dr. D. Michael Young, Dr. William J. Young, and Dr. Kenneth L. Zierler. I also wish to acknowledge the invaluable advice and encouragement of my colleagues Dr. Carl P. Swanson and Dr. William D. McElroy, and Mr. Reuben Shiling. It is a pleasure to express my appreciation to Mr. Charles Halgren and Mr. Joseph B. Whitton and their staff at the CARU Studios for the fine art work, to the Marine Biological Laboratory at Woods Hole, Mass., for the use of its excellent library, and to Mrs. Jean Gadziola and Mr. Reginald H. Garrett for their general assistance and cooperation. I also wish to thank my present and former students and associates for their numerous suggestions.

In particular I am deeply indebted to my wife, Thelma, for many things. Her patience, comfort, interest, and understanding made the writing of this book possible.'

Alvin Nason
Baltimore, Md.