from The Textbook Letter, March-April 1997

Reviewing a high-school book in biology

Biology: Principles and Explorations
1996. 1072 pages. ISBN of the teacher's edition: 0-03-073573-4.
Holt, Rinehart and Winston, Inc.,
1120 South Capital of Texas Highway, Austin, Texas 78746.
(This company is a division of Harcourt Brace & Company,
which is a part of Harcourt General Inc.)

A Mediocre Book Built Around a Gimmick

William J. Bennetta

Biology: Principles and Explorations is an overdone, overstuffed, mediocre textbook built around a sales gimmick. Holt's advertising proclaims this book to be both innovative and up-to-date, but I am not convinced. If I disregard the gimmick and concentrate on the book's content, I find that the Holt writers have assembled a great mass of conventional material, have recycled a lot of conventional mistakes and misconceptions, and have labored to sustain the thoroughly conventional, thoroughly discredited notion of "nature's ladder."

The sales gimmick consists of the odd way in which the material is organized. The body of the book is divided into two major chunks called "Part 1: Biological Principles" and "Part 2: Biological Explorations," apparently representing Holt's attempt to have things both ways. I infer that Holt's writers and editors wanted a book which would seem to take account of recent efforts to reshape, reduce and refocus the high-school biology curriculum, but they evidently could not make themselves abandon the conventional practice of mentioning everything and anything that anyone, anywhere, might want to see in a biology book. Principles and Explorations is one of the fattest and heaviest high-school biology textbooks that I have seen, and it seems to mention everything at least once.

The blast of advertising at the front of the teacher's edition starts with a "message" from two professors who are said to be the book's "authors." These two claim that "In every area of the text, from warm-blooded dinosaurs to DNA fingerprinting, we have presented an account of the state of science that is as up-to-date as possible." Given that some of the stuff in this book is out-of-date by decades or even centuries, I must infer that the professors harbor a rather odd perception of the current "state of science." Or maybe they haven't done much reading of the book that they allegedly wrote.

Later in their "message" they make a lame attempt to link the book to the National Research Council's National Science Education Standards, even though Principles and Explorations was produced before the NRC standards were published. [See "Concentrated Hokum and Standard Malarkey" in TTL, July-August 1995.] Then the professors try to plug this big, bloated text as a solution to the problem of big, bloated texts:

Today's texts simply contain too much material for any one course to teach. A new curriculum must provide thorough coverage of the basic principles, and flexibility to allow teachers to explore the details of the topics they want their classes to concentrate on. Biology: Principles and Explorations does both.

This presumably gets the teacher ready to be dazzled by the book's two-part organization, which is described as the advertising continues. Holt claims that Part 1 (which comprises four units and eighteen chapters) covers "fundamental content that lies at the heart of any biology curriculum," while Part 2 (five units and twenty-four chapters) is devoted to "diversity." But wait -- there's more. Each of the five units in Part 2 has an "Overview" chapter, and the five "Overview" chapters (Holt claims) can be joined to the eighteen chapters in Part 1 to yield a basic biology course:

As long as the eighteen core chapters [in Part 1] and the five OVERVIEW chapters [in Part 2] are covered, your students will obtain a well-organized exposure to the basic principles of biology, as presented in the new National Science Education Standards, and an excellent preparation for college work.

Are you confused? So am I. If teaching the "basic principles of biology" requires the use of those "Overview" chapters, why were those chapters not placed in Part 1 with the rest of the "fundamental content"?

Cookbook "Science"

In assessing the book's scientific content, I have focused on the writers' treatment of evolution, the general biology of animals, and the biology of humans -- subjects in which I am particularly interested. I also have tried to judge whether, as Holt claims, students who use this book will be able to learn "the basic principles of biology."

My chief finding is that the material is wildly variable in quality, ranging from real science to fairy-tales and arrant nonsense. I infer that the various chapters in Principles and Explorations were produced by many different writers who varied considerably in their familiarity with science and their ability to rephrase from older texts.

The book starts very poorly, as the writers repeat the traditional claim that scientific research is a cookbook activity that always proceeds through a series of fixed "stages":

Although there is no single scientific method, all scientific investigations can be said to have six stages: collecting observations, forming hypotheses, making predictions, verifying predictions, performing control experiments, and forming a theory. [page 8]

That is rubbish. The trite notion that scientific work always includes controlled experiments (or "control experiments," in Holt's lingo) is false, but our schoolbook-writers continue to copy it and recopy it, year after year after year. It is especially ridiculous in the book at hand, since so much of the scientific information in this book obviously has not been derived from experiments. (I wish that I could spend a few minutes with those two professors, so I could ask them to describe the "control experiment" that was used in discovering which phyla are represented in the Burgess Shale, or how aphids feed, or where the jaguar dwells, or how a frog's lungs are constructed. I'd also like to hear their notion of what the word theory means. The claim that all scientific investigations culminate in "forming a theory" is ignorant cant.)

As if to make sure that students won't learn what natural science is about, Holt's writers go out of their way to misrepresent the scope of science and to blur the boundaries between science and religion. In their chapter "The Origin of Life," they include an evasive, grossly misleading passage on "Divine Creation," in which they tell students that

Traditionally, many cultures have believed that life was put on Earth by divine (relating to a god or gods) forces, as the act of a creator or creators. Belief in divine creation is common to many of the world's major religions, though the accounts of creation vary from one religion to another. . . . Because the idea that life originated through divine creation cannot be tested by scientific methods, it falls outside the realm of science. This is not to say that the belief is wrong, but rather that science can never test it.

Correct; the vague, nondescript idea that "life originated through divine creation" cannot be tested scientifically. But many of the specific assertions embedded in specific creation myths certainly can be tested. If a religious tale includes a claim about the natural world (i.e., the world which we can apprehend with our senses, and which is the province of natural science), we can evaluate that claim scientifically. We can test it against evidence -- and the fact that the claim has been promulgated in a religious context doesn't matter at all.

As an example, consider a tale that is widely known in our own society: the story of Noah and the Flood, which is a part of the second creation myth in the Holy Bible. This story is surely religious, but it also contains explicit and implicit claims that deal entirely with the natural world and that can be tested against our knowledge of paleontology, stratigraphy, biogeography and vertebrate physiology, among other things. When examined in this way, the claims have failed miserably. Fundamentalists may believe that the narrative of the Flood is a literal account of events in the real world, but we know that this belief is wrong. Science has discredited it conclusively.

As another example, please recall the belief -- common and widespread among fundamentalists -- that Earth came into being, by divine creation, only a few thousand years ago. This belief proceeds from an elaborate religious construct, to be sure; but even so, the specific assertion that Earth is only a few thousand years old is a testable claim about nature. It therefore lies squarely within the realm of science, and science has shown it to be false.

Instead of citing any concrete cases like these, Holt's writers have resorted to fuzzy stuff that misleads students and avoids the very point that students must grasp. Let me repeat that point: If a religious claim deals with the natural world, we can test that claim scientifically; the fact that the claim has been promulgated in a religious context doesn't matter at all.

This principle isn't restricted to the examination of old creation myths, of course. It applies just as well to the analysis of claims made by today's faith healers, relic-mongers and other proprietors of religious businesses, and this is all the more reason why textbook-writers must elucidate it well. Why have Holt's writers done the opposite?

Inconsistency and Contradiction

The treatment of organic evolution in Holt's book is inconsistent and fraught with self-contradiction.

Evolution first appears in Part 1, where it commands chapters 11 through 14. Chapter 11, "The Origin of Life," is sullied by the aforementioned "Divine Creation" stuff and by deliberate fuzziness in a passage about the age of Earth, but then it gets better. I especially like the section "Does Spontaneous Origin Violate the Second Law of Thermodynamics?" (No, it doesn't, and the writers explain this well.) Chapter 12, "Theory of Evolution," is acceptable. The pseudohistorical section called "The Work of Charles Darwin" is not entirely reliable, but it is better than the folktales that some other high-school textbooks have peddled as accounts of Darwin's work. The rest of the chapter is a competent survey of the usual topics, including some of the mechanisms that keep evolution going.

Chapter 13, "History of Life on Earth," barely achieves mediocrity. It's too short to be good, some topics are compressed to the point of incomprehensibility, and the writers recite dogmatic fancies like these:

Amphibians are an imperfect solution to the challenge of living on land. They must return to water to reproduce, and they must live in moist places because their bodies are in constant danger of losing too much water through their skin by evaporation.

The first claim is silly: Amphibians are surely "imperfect" in their efforts to meet "the challenge of living on land," but so are all other terrestrial organisms. The second claim is a false generalization: Some amphibians breed in water, some do not. The third claim, another generalization, is equivocal and misleading. All three claims are clichés that reflect the notion of "nature's ladder" -- and there are plenty more where those came from, as we shall see.

Chapter 14, "Human Evolution," strikes me as pretty good, though I wish that the writers had identified the evidence that supports some of their statements about the history of our lineage. (I doubt that students will know what kind of evidence indicates that, some 36 million years ago, nocturnal primates became diurnal.) More serious difficulties arise when the writers reject science and promote anthropocentricity, as they do in this passage:

Language has allowed us to transmit accumulated experience from one generation to another. Thus, humans have what no other animal has ever had -- cultural evolution.

Wrong. Humans are not unique in displaying cultural evolution, just as they are not unique in having language or in transmitting experience between generations.

Another injection of anthropocentricity is administered in figure 14-5, a diagram of primate phylogeny: The diagram has been rigged to teach that intraspecific variation in humans is important but variation in other animals is insignificant or nonexistent. (The same lesson is urged in several other diagrams in this book.)

In Part 2, the treatment of evolution is vexatious. I've given special attention to how Holt's writers, editors and artists have handled the evolution of animals, and I've found both good features and bad.

What's good is the stuff dealing with phylogenies and chronologies. Holt's people deserve praise for continually showing their readers that animals have histories, and for trying to get the facts right. In reading their material that addresses phylogenies and chronologies per se, I have found only a few serious errors. (For example, the writers twice call Dimetrodon a reptile, and on page 748 -- in a muddy passage that is hard to interpret -- they seem to say that sharks were the first animals to develop true bone.)

Their good work is more than offset, however, by their clinging to the traditional pretense that evolution is a linear process in which animals grow increasingly "complex" and increasingly man-like, moving toward organic perfection. That is, of course, a restatement of the "nature's ladder" doctrine -- an anthropocentric construct that was definitively rejected by science, in the 19th century, because it couldn't accommodate facts gathered in the real world. Holt's people continue to plug it, however, using all the crankish stuff that textbook-writers have devised for this purpose. They tell the customary, misleading story about vertebrate hearts. They repeat the usual folktale about breathing mechanisms in fishes. [See "Deep Breathing" in TTL, July-August 1996, page 9.] And to no one's surprise, they use false or misleading claims to create a bogus picture of linear improvements in vertebrate modes of reproduction. Here, for example, are the four headlines in their section about how vertebrates breed:

Fishes Fertilize Their Eggs Externally [That is false; some fishes do, some fishes don't.] Amphibians Are Still Tied to Water [False again; some amphibians are, some amphibians aren't.] Reptiles, Birds, and Mammals Have Internal Fertilization [But so do many other animals, vertebrates and invertebrates alike.] Mammals Nourish Their Young [So do many other animals, vertebrates and invertebrates alike.]

This performance is topped off with a novelty number, as Holt's writers invent the notion that "amphibian development takes place in two phases" because an amphibian's body "is far more complex than that of a fish"! Their entire passage is tripe. [See "Examining Holt's Novel Nonsense."]

All in all, the treatment of evolution in Principles and Explorations merits a C, but this book's version of the biology of animals gets a big, red F. In trying to make animals conform to the old, imaginary ladder, Holt's writers have scorned science. And whether they know it or not, they have mocked and contradicted the material about evolution that appears in Part 1 of their own book.

Some Gold, Some Dross

The material that is explicitly called "human biology" in this book -- eight chapters in Part 2 -- is a strictly conventional, mistitled presentation of anatomy and physiology. The writers ignore everything else, neglecting to consider even the most basic questions that we would ask about any species of animal. (What do these creatures look like? How are they distributed on Earth? How do they compete for reproductive opportunities? And so forth.)

Some human ecology turns up in earlier parts of the book, for better or for worse. In the chapter "Human Impact on the Environment," the treatment of global warming is inadequate and rather misleading, but the section about damage to ecosystems includes a paragraph that is pure gold:

You should not be lulled into thinking that extinction is a problem limited to the tropics. The ancient forests of the northwestern United States are being cut swiftly, largely to supply jobs, and much of the cost of logging is subsidized by our government (the U.S. Forest Service builds the necessary access roads, for example). At the current rate, very little of these ancient forests will remain in a decade. It is hypocritical of us to scold tropical nations for destroying their rain forests when we do such a poor job of preserving our own country's species.

The same chapter has a section titled "The Core Problem: Population Growth," but the writers shrink from saying anything substantive about how that "core problem" can be tackled. They tell that some nameless "countries" are making progress toward slowing the growth of populations, but they don't tell how; they cite reductions of family size in Thailand and Mexico, but they don't say how these reductions were attained; and they fail to point out that in some countries, such as the United States, much of the growth in population is due to immigration.

As a whole, Principles and Explorations has little that is new and too much that is antiquated, equivocal or just dumb. I don't think that this book matches Holt's claims, and I can't recommend it.

This Book May Suffice for Traditional Teaching

Lawrence Davis

Biology: Principles and Explorations is evidently the F1 offspring of two previous Holt texts -- Biology Today and Biology: Visualizing Life -- and it shows a certain hybrid vigor. It also, unfortunately, expresses some undesirable dominant traits that seem to have come primarily from the Biology Today side of its pedigree.

[Editor's note: Lawrence Davis has analyzed those two earlier books in The Textbook Letter. His review of Biology Today was published in our issue for March-April 1993, and his review of Biology: Visualizing Life ran in our issue for May-June 1994.]

Visualizing Life was a marked departure from the traditional biology-book format. It used an abundance of illustrations, and used them intelligently, while text was kept to a minimum but was rendered with high precision. It also seemed to have been designed with Jesse Jackson's Rainbow Coalition in mind, because it had pictures and biographical profiles that presented people of many sizes, shapes and colors.

Principles and Explorations returns to a heavy dependence on text, sometimes loses accuracy, and seems to be a book for and about white males. In the pictures, scarcely anyone is shown doing science, and women are almost always shown in traditional roles or at play. (An exception: Page 176 has a picture of Barbara McClintock, a modest botanist who won a Nobel Prize for her discovery of transposons.) Holt's editors and illustrators seem to have returned to an outmoded view of things, even in their depiction of Neanderthalers (page 307). I think this is a real mistake -- especially because, if present trends continue, about one-third of the PhD degrees that will be earned by our present cohort of high-school students will be earned by women. It appears that someone hopes to turn back the clock.

How did this book happen? Holt says that the book's authors are George B. Johnson and Peter H. Raven, both professors at Washington University. In "A Message From the Authors" in the teacher's edition, Johnson and Raven mention the National Research Council's standards for science education and say that Principles and Explorations is organized around "a small number of key concepts and ideas in areas such as cell biology, genetics, evolution, ecology, and diversity." They recognize that "There is a great disparity around the country concerning mandated content," and they conclude by inviting the teacher to "Turn the page to see how Biology: Principles and Explorations allows you to tailor your teaching to meet your curriculum needs."

Turning the page, the teacher reads that the book can meet diverse curriculum needs because it has two parts.

Part 1, called "Biological Principles," has eighteen chapters distributed in four units: "Principles of Cell Biology," "Principles of Genetics," "Principles of Evolution" and "Principles of Ecology." The cell-biology unit is pretty sophisticated stuff, at about the level of an introductory course in biochemistry. The genetics unit is predominantly molecular and is as sophisticated as the cell-biology unit. The evolution unit has nearly 100 pages, is well done and gets right to the point, starting with Darwin; there is no major waffling here. Ecology is a big field to treat in 100 pages, but the ecology unit is reasonably successful.

Part 2, titled "Biological Explorations," consists of units 5 through 9 -- twenty-four chapters that fill some 600 pages. Each unit has a long "Overview" chapter and then some supporting chapters that give details. Unit 5 surveys biotic diversity, then looks at viruses, bacteria, protists and fungi. Unit 6 does plants, Unit 7 sweeps through invertebrates, Unit 8 treats vertebrates, and Unit 9 probes the human body.

The publisher says that the eighteen chapters in Part 1 plus the five "Overview" chapters in Part 2 will suffice to cover all the principles of biology prescribed in the NRC standards. This may be true, and teaching those twenty-three chapters may well consume the entire school year.

What is the use of the other chapters, then? The human-biology unit alone offers eight chapters, spans 190 pages, and could serve as the text for a one-semester course in human physiology (if it were judiciously combined with material from Part 1). However, it couldn't be used for teaching anything about human sexuality, because the external genitalia are hardly acknowledged; in fact, those of the female are entirely ignored. The only identified means for limiting reproduction are abstinence and barrier methods. Hormonal cycles are mentioned, but their implications for the management of reproduction are not spelled out.

The unit on plants seems to be very well done. It would furnish the basis for a modern course in botany and plant physiology if it were combined with the chapter on photosynthesis (in Unit 1) and the relevant material on plant genetics (in Unit 2). Similarly, a survey of zoology could be constructed by drawing material from various parts of several units. So one has the resources here for fashioning several different biology courses within a traditional framework.

It is clear, however, that the full amount of material in this book is much more than could be assimilated, even by outstanding students, in a single-year course. Most students would be overwhelmed and intimidated by the book's sheer mass and density.

I showed Principles and Explorations and Holt's Visualizing Life to three above-average students who recently had had good biology courses at their respective high schools, and they judged Visualizing Life to be much more appealing. One student likened Principles and Explorations to a college textbook that she had used in an advanced high-school course in cell biology. All three students, however, thought that Principles and Explorations had a cool cover.

Disappointing Material

All of the chapters in Principles and Explorations have "Laboratory Investigation" activities, but about a third of them, unfortunately, are really just learning exercises conducted with pencil, paper and prepared materials. In my view, these don't qualify as laboratory work. The project in chapter 5, for example, is called "Chromatography of Plant Pigments," but students don't actually extract or separate any pigments; they work with "simulated plant pigments" that come from a kit. The activity in chapter 14 deals with skulls, but the students don't actually handle skulls; they just measure marked distances on drawings of skulls. (A separate lab manual is apparently available for use with Principles and Explorations, and it may provide better opportunities for students to do real lab work.)

As usual, the illustrators have let the writers down. This book's first chapter has a traditional description of "The Scientific Process," which is said to require "careful observation" -- yet Holt's artists have not kept their eyes open. On page 320, for example, we have a graph that purportedly shows population growth over the ages, with a caption saying that the Black Death "may have killed up to 50 percent of Europe's population between 1347 and 1352." On the graph itself, however, the decline labeled "Black Death" begins at about the year 850 and continues to 1250. The graph also shows that the world's population before the coming of the Black Death was about 700 million; but a later graph, on page 399, looks much different and indicates that the world's population didn't reach 500 million until the 17th century. How did two graphs showing such disparate information get into the same book? If illustrations are not important, why have them? If they are important, why not do them correctly?

Figure 15-3, supposedly illustrating the concept of population density, is a howler. The artist shows four tortoises on a small island, then four tortoises on a large island whose lineal dimensions are double those of the small island. Doubling the lineal dimensions has quadrupled the available area, reducing the population density by a factor of 4, but the caption says that the population density has changed by a half. This is a kind of fundamental misconception that we continually struggle to overcome in our students. Textbook-writers, I beg you: Don't confuse them!

Page 59 of the teacher's edition has a "Demonstration" note which propagates another misconception: the notion that if dye is added to a jar of water, it spreads through the water by "the process of diffusion." Wrong! The dye is dispersed by convection, and there is a world of difference between those two phenomena. For a single cell, taking advantage of the high rates of mass transfer offered by convective flow, instead of depending on the much slower process of diffusion, can literally be a matter of life or death. When we teach physiology, we have a responsibility to do it right. Stephen Vogel has addressed this matter, and has described some legitimate ways to demonstrate diffusion, in the October 1994 issue of The American Biology Teacher.

Like most reviewers, I am particularly bothered when textbook-writers blunder in their treatment of my own field. Two years ago, when I reviewed Holt's Visualizing Life, I found that its discussion of my specialty, the biological fixation of nitrogen, was short and completely correct. Now, in Principles and Explorations, I find atavism. Holt's writers have reverted to using an old, erroneous claim in the book's text (on page 215), and they apparently haven't noticed that this claim is contradicted by the definition of nitrogen fixation in the book's glossary (on page 1046). The glossary item is correct: Nitrogen fixation yields only ammonia -- not nitrates or nitrites. Another mistake appears in the illustration on page 353, which indicates that nitrogen-fixing bacteria release free ammonia directly into the soil. They don't. It would be convenient for humans if they did, but it would be very maladaptive for the bacteria.


Holt's editorial team has succeeded, in large measure, in their attempt to touch all the bases, and they have done this with reasonable accuracy though without much excitement. For traditional-style teachers and traditional-style learners, this textbook may suffice. For today's video generation, however, Visualizing Life would be a much better choice.

William J. Bennetta is a professional editor, a fellow of the California Academy of Sciences, the president of The Textbook League, and the editor of The Textbook Letter. He writes frequently about the propagation of quackery, false "science" and false "history" in schoolbooks.

Lawrence Davis is a professor in the Department of Biochemistry at Kansas State University (Manhattan, Kansas). He specializes in the biology and chemistry of nitrogen fixation.


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