This article appeared in the
in The Textbook Letter, March-April 1998.
In fishes and amphibians, fertilization occurs externally,
and the zygote develops in the water.
Who would tell such a thing to young people who are trying to learn biology? Schoolbook-writers would -- and a lot of them do. The particular sentence that I have quoted appears in BSCS Biology: An Ecological Approach (which is reviewed in this issue of The Textbook Letter), but similar categorical statements, all absurd, appear in many biology books and life-science books. Such statements help to sustain the notion of "nature's ladder" -- the belief that organisms form a continuous series which begins with lowly, "simple" creatures, ascends through organisms that are increasingly "complex" and man-like, and culminates in man himself.
"Nature's ladder" has no basis in science, but the schoolbook-writers like it. They evidently believe that it makes their books more salable because it affirms vulgar superstitions.
These ladder-peddlers cast the amphibians as inadequate animals that don't merit serious attention, and they show no mercy at all to the fishes. They dismiss the fishes with overt scorn, they hide the fishes' morphological, physiological and behavioral diversity, and they take special pains to deny the spectacular diversity that scientists have seen in the fishes' modes of reproduction. Because the scientific facts don't comply with the doctrine of the ladder, the ladder-peddlers discard the facts and replace them with rubbish like "fertilization occurs externally, and the zygote develops in the water." Sometimes they even add the claim that external fertilization is an unreliable process in which many eggs are left unfertilized. That is a lie, but it helps to ensure that students will get the message: Fishes are clumsy, inept creatures, and they lack the reproductive refinements possessed by the nice, warm, proper animals (i.e., birds and mammals) that dwell on the higher rungs of the imaginary ladder.
This is too bad, because no student can develop a scientific understanding of the vertebrates unless he has some genuine knowledge of the fishes. Most vertebrates are fishes, and the fishes' vast diversity teaches many important lessons about evolution.
I have called attention to these matters before, in reviews of such textbooks as Heath's Life Science: The Challenge of Discovery, Holt's Biology: Principles and Explorations, and Glencoe's nonsensical Biology: Living Systems. Now I'd like to recommend an outstanding book that will help biology teachers to convey some real ichthyology to their students, in place of the nonsense favored by the ladder-peddlers. The book is Encyclopedia of Fishes, published in 1995 by Academic Press. Aimed at the intelligent layman, it offers clear and careful writing, magnificent photographs, superb factual accuracy, and countless examples of fascinating adaptations.
The structure of Encyclopedia of Fishes is straightforward. Part One (44 pages) provides an introduction, then four short chapters that deal successively with the classification, paleontology, ecology and behavior of fishes, and then a chapter on endangered species. Part Two is a 181-page survey of "Kinds of Fishes," arranged by orders and families. (There are about twice as many orders of fishes as there are orders of mammals, though most biology books and life-science books keep this a secret.) The survey is rich in information about the distribution, diversity and natural history of particular groups, with appropriate attention to their reproductive mechanisms and strategies. After you've spent a couple of hours with this beautiful and insightful book, you'll laugh at the ladder-peddlers' claim that all the fishes share a contemptibly simple mode of reproduction in which "fertilization occurs externally, and the zygote develops in the water."
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 often about the propagation of quackery, false "science" and false "history" in schoolbooks.
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