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248 THE EXFE SCIENCES Within each research area a few individuals are engaged in comparative studies either within a single phylum or plant division or across several phyla or plant divisions. Although students of evolution and systematic biology were the most numerous such group, these were only 44 of the 123 individuals so engaged. WITH WHAT SPECIES DO LIFE SCIENTISTS WORK? The diversity of living nature never fails to astonish. The workings of evolution have resulted in millions of distinct species of living forms, uni- cellular, plant, and animal, all located in the thin web of life, which is a film on the surface of our planet. These are the objects of study for life scientists. But which species should one study? The answer depends upon the question that has been raised. Some species are of interest because they are the basis of our agricultural economy. Some make the world more beautiful and exciting; some cause disease of man, plant, or animal. Some- times even the most obscure species provide excellent models for study of complex biological phenomena. And surely a proper object for study by man is man himself! Thus there are valid reasons for the study of a great variety of species. Some species are of interest because they are intermediate links in a food chain, because they survive under what appear to be improbable conditions, or because they represent evolutionary extremes. Still others are of interest because they offer unique opportunities to study phenomena of general importance but difficult to analyze or observe in more common species. For example, the nerve net of the crab is of interest as a prototype of the more complex nervous system of the mammal; the response of cer- ta~n Insects to sugars can serve as a model for some aspects of the physi- ological bases of behavior; the "alarm reaction" of the clam is highly instructive with respect to certain reflex activities; the photosynthetic prop- erties of the chromatophores of purple bacteria and of certain algae are more readily studied than is photosynthesis in a higher plant; regulation of the genome of a bacterium serves as a model for the process of differen- tiation in a higher organism; and the giant axon of the squid is the favorite test object of numerous neurophysiologists. Nutritionists long since seized on the omnivorous white rat as a model for human nutritional requirements, but primates may be more instructive with respect to human behavior or reaction to disease. The pig offers a surface area and mass somewhat com- parable to that of man, and thus should serve as a model for human re . , ,

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THE WORLD OF BIOLOGICAL RESEARCH 249 spouse to radiation. Comparison of the properties of hemoglobins from a wide variety of species elucidates those properties of the hemoglobin molecule that are imperative to its physiological function, and frog muscle has taught us much of what we understand of muscle physiology and its molecular aspects. The list is well-nigh endless. And so it is that life scientists continue to study or exploit the properties of a great diversity of organisms. In a highly compressed form, this is displayed in Table l5. Each of the respondents to the questionnaire was given a choice of 58 genera, phyla, or larger divisions of the plant, animal, and microbial kingdoms and was asked to indicate no more than two that most closely described the objects of his study. Hence, the number of specific responses exceeded the number of respondents. But hundreds of investigators indicated that necessarily and properly they should indicate more than two such entries. Perhaps the aggregated totals are of greatest interest: 21 percent of all scientists dealt with one or another micro-organism, l5 percent with plant forms, and 54 percent with animal forms. None of the categories of living forms was totally ignored by the current activities of life scientists but, clearly, some are more attractive than others. Viruses and bacteria are the concern of scientists in each research area, particularly those who study disease mechanisms, cell biology, and molecular biology and biochemistry. Lower plants engage the attention of all but the nutritionists and phar- macologists, while higher plants attract the attention of all but the pharma- cologists. Invertebrates are of great interest to the ecologists and the systematists as well as to the behavioral biologists, who see in them models for the behavior of more advanced forms. Surprisingly little attention is being given to the species of fish that dominate our commercial harvests, whereas other fish, amphibia, reptiles, and birds are receiving greater atten- tion. Of the mammalia, man and the common laboratory rodents are the most frequent study objects. The great utility of the latter is indicated by the fact that, whereas ecologists and systematic biologists pay them scant heed and only 6 percent of all geneticists make use of their particular attributes, these species are utilized by 12 percent of the behavioral biol- ogists and 37 percent of the pharmacologists. Domestic mammals, i.e., cats and dogs, are particularly useful to the physiologists, pharmacologists, nutritionists, and morphologists and are used to some degree by almost all other groups. ~ ~ 1 ~ ~ ~ A ~ _ _` ~p TEA Although ~ percent or all behavioral OlO~OglStS and ~ To;; o' ` morphologists report that they work with small primates, primates are little 1 "7 ~ ~ _ _ . ~ ~ . ~ ~ _ _ ~ T Y ~ ~ ~ ~ A ~ ~ ~ ~ + ~ +h; ~ L used by workers m other sclentl~c areas. However, mere is reasoIl ~o ~1111~ that this reflects not the utility of these species, but the great costs involved in

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