Pop quiz today: What is wrong with the following statements?

* All mammals are "covered with hair or fur."

* An embryo is a "developing egg."

* "To survive in a changing environment, organisms must adapt."

Two things are wrong. The statements are erroneous, and they appear in newly published high school biology textbooks.

They are among scores of errors and inadequacies cited in a study of 18 biology texts now being offered for use by schools.

By far the most significant defect, according to two biology teachers who made the study, is that half of the books fail to give adequate coverage of evolution and one-sixth do not even mention the word.

Although evolution theory is the central paradigm of biology -- the set of facts and ideas that makes all the observations of biology fit into a coherent picture -- the study found that biology texts, on the whole, cover the subject more poorly than books did almost 20 years ago.

"The quality of biology textbooks has declined drastically since the late 1960s," said Wayne A. Moyer of People for the American Way, a private organization that combats censorship of texts and library books and which sponsored the study.

Moyer, a former biology professor and former director of the National Association of Biology Teachers, conducted the study with William V. Mayer, professor emeritus of biology at the University of Colorado.

"Textbooks improved as a result of the renaissance in science education following the launching of the Soviet spacecraft Sputnik in 1957," Moyer said. "But in recent years publishers have given in to pressure from the ultrafundamentalists and watered down references to evolution and other scientific theories."

The three books criticized for not even mentioning the word "evolution" are "Life Science," published by Scott, Foresman & Co.; "Living Things" by Holt, Rinehart & Winston, and "Biology for Living" from Silver Burdett.

On the other hand, the study, "A Consumers Guide to Biology Textbooks, 1985," singles out three textbooks as "doing an excellent job of presenting evolutionary theory and covering the field of biology." These are "Biological Sciences: An Ecological Approach," published by Houghton Mifflin Co., "Biology" by Macmillan, and "Biology" by Addison-Wesley.

In addition to numerous examples of careless presentation of biological information -- such as neglecting the fact that some mammals, such as whales, are hairless and that embryos are far more developmentally advanced than eggs -- the study concentrates on poor or absent explanations of evolution.

For example, one book says that "to survive in a changing environment organisms must adapt."

This, the study says, teaches the long-rejected Lamarckian view that an individual animal that changes can pass those changes on to its offspring. In fact, it is species or populations within species that adapt. The change does not occur within individuals but from one generation to the next.

Another text offers the following: "Millions of species have evolved successfully while others have become extinct."

This, the study says, suggests that extinct species were unsuccessful. In fact, for a species to appear in the first place, it would have to be successful. The dinosaurs -- their very name an epithet for failure -- were among the most successful groups of animals, thriving for 150 million years.

Yet another mispresentation of evolution theory emerges from one text's discussion of the various ancestral forms of the modern horse. "Many of the intermediate forms of horses are found in rocks of the same age," one text says. "This indicates that they lived at the same time and that one could not have evolved directly from the other."

Contending that this statement reflects creationism, the study notes that when a new species arises, it does not usually replace its ancestral species. If the two species are adapted for different ecological niches, they may coexist happily. Several species of African antelopes, for example, have evolved from common ancestors but share the same habitat by specializing in eating different plant species.