Showing papers in "BioScience in 1972"

Natural Abundance of the Stable Isotopes of Carbon in Biological Systems

Abstract: About 99% of all carbon is the 12C isotope while 1% is 13C. The other isotopes of carbon are, by comparison, extremely rare. For instance, only about one atom in every 1012 carbon atoms is 14C. The precise ratio of the isotopes will vary depending on the material analyzed. Limestones, atmospheric C02, marine algae, and land plants each possess characteristic 13C/12C ratios, differing slightly from one another. The lowest ratio so far observed is for carbon from ancient blue-green algal mats (Kaplan and Nissenbaum, 1966) and the highest for carbonate carbon from meteorites (Clayton, 1963). Fractionation of plant carbon is brought about primarily by carbon dioxide assimilation in photosynthesis and is due to preferential utilization of 12C and exclusion of 13C. Curiously enough, it has been found recently (Tregunna et al., 1970) that higher plants which fix carbon dioxide via the Calvin cycle pathway differ in 13C/12C ratios from plants which fix carbon dioxide via the C4-dicarboxylic acid pathway. Thus, it is now possible to determine whether a given sample of sucrose was synthesized in sugarcane or in sugar beet. While it is the aim of this paper to discuss a few recent studies on naturally-occurring 13C/12C ratios of biological materials, it is pertinent to note that the subject has been reviewed from a geochemical viewpoint (Bowen, 1966; Degens, 1969; Kroepelin, 1966; McMullen and Thode, 1963; Schwarcz, 1969). The various isotopic species of an element differ slightly in chemical properties from one another. Just as the chemical properties of different compounds determine their formation under various conditions, so the chemical properties of different isotopic species of the compounds will determine how the isotopic abundances distribute themselves in nature. Thus substitution

Controlled Eutrophication—Increasing Food Production From the Sea by Recycling Human Wastes

Abstract: Eutrophic systems, on the other hand, rarely achieve the status of a stable, climax community. The continuous supply of nutrients to these environments sustain high levels of photosynthetic production. If processes of advection or decomposition of the resulting living and dead organic matter cannot keep pace with its rate of production, this material may accumulate to the point where it exceeds the carrying capacity of the water. These extreme conditions lead to the development of anoxic and eventually abiotic environments. Even when a balance between the production and loss of organic matter produces a quasi-steady state, small perturbations in physical and chemical parameters (radiation, nutrient input, temperature, etc.) cause photosynthesis and respiration to vary widely in absolute terms and with respect to each other. Long-term balance and stability are not readily achieved under such conditions. Eutrophic communities tend to be either highly productive or respiratory, and when the oscillations become great enough, periodic mortalities occur. The alternation between productive and destructive processes that takes place in these eutrophic environments has a pronounced effect upon the kinds of biological communities that inhabit them. As mentioned above, succession leading to a stable and diverse climax community is not possible. The larger, slow-growing carnivores high on the food chain do not prevail, at least as resident populations. Small herbivores that can reach maturity in weeks to a few months, whose populations can respond quickly to favorable conditions and recover rapidly from mortalities, predominate. This is true particularly of the fixed benthos, but is also typical of the pelagic fish populations, which are characterized by small, rapidly growing species such as herrings, sardines and anchovies that can avoid the deeper, anoxic layers, are short-lived and subsist on plankton near the base of the food chain. Furthermore, as eutrophication increases, an increasingly larger fraction of the organic production becomes channelled into species that are too small or otherwise unsuitable or useless as food for man. In the absence of a

Feeding and Digestion in Some Ants (Veromessor and Manica)

Abstract: sloping downwards, and of horizontal 0.5-1.0 cm high nest chambers. We have not yet excavated a complete nest, but the chambers reach into the permanently moist lower soil layers where the temperature is practically constant the year around. On cool winter days any foraging is done during midday; when in spring and summer the midday air temperatures reach 30 C and above and the ground surface becomes even warmer in the sun, foraging is restricted to a few early morning and later afternoon hours, starting in or lasting into darkness. Therefore, these ants live an air-conditioned life, never are exposed to extremes in temperatures, and stay in a dry atmosphere for only short periods; even in a dry desert soil, at some depth the relative humidity remains high throughout the year. Observing a nest near our laboratory trailer in Death Valley, it was found that each day the direction of the food-gathering column of workers was shifted clockwise about 150. In such a column the worker ants continued in closed ranks with no scouting along the edge, fanning out only in the last 10 m of journey. Since most workers returning to the nest carried a seed, fruit, flower stem or other object of prospective food value, an ant continued in the collecting column until she found a "usable" object and then immediately returned.

Newton's Law: Its Application for Expressing Heat Losses from Homeotherms

Abstract: The applicability of Newton's law of cooling as a means of expressing heat losses from homeothermic animals has geen discussed at length in recent literature (Kleiber 1961, McNab 1970, Strunk 1971). Although this law has been used extensively (Scholander et al. 1950, Tucker 1965, Dawson and Schmidt-Nielson 1966, Herried and Kessel 1967, McNab 1966, Henshaw 1968), the relationship between Newton's original law and the Newton's law used by biologists today is at best remote (Strunk 1971, Kleiber 1961). Strunk (1971) has argued against the use of Newton's law as a biological model in favor of models that are based on the physical principles of heat loss from animals. McNab (1970) states that simple biological variability makes impractical the use of the more mechanistically correct equations, and Newton's law is perhaps a good pragmatic approach for expressing heat loss from homeotherms. This paper reports a theoretical examination of some similarities and differences between Newton's law and the thermodynamic energy balance as they have been used to describe heat losses from homeothermic animals in artificial and natural environments.

Mercury: Its Occurrence and Effects in the Ecosystem

Abstract: Mercury levels in marine fish have not increased in recent years. The amount released annually by man is about 10/sup 4/tons compared with 10/sup 8/tons present in the ocean. Thus, without some subtle concentration mechanisms, man's activities cannot appreciably alter the levels in the total ocean. The direct human health hazard of environmental mercury appears to be limited to those persons for whom fish is a dominant part of their diet. The concentration of mercury in the aquatic food-chain combined with transformation into methyl mercury are the causative factors in this problem. The finding of increased chromosome breakage associated with elevated levels of blood in persons eating fish regularly and concentration across the placenta suggests that the currently accepted level of 0.5 ppm does not have an appreciable margin of safety for pregnant women. For wildlife the hazard appears to be appreciable for two groups. The first are the seed-eaters feeding directly on seeds pretreated with mercurials. The second is birds at the top of the fresh-water food chain. 69 references, 3 tables, 1 figure.

Role and Function of Humus in Soil with Emphasis on Adsorption of Herbicides and Chelation of Micronutrients

Abstract: Soil organic matter, generally referred to as humus, is a truly remarkable substance in that the small amounts found in productive agricultural soils, generally representing less than 5% of the dry weight, imparts unique and remarkable properties to the inorganic matrix of sand, silt, and clay. Humus serves as a source of nitrogen, phosporus, and sulfur for higher plants; improves structure, drainage, and aeration; increases water-holding, buffering, and exchange capacity; enhances the dissolution of silicate minerals; and serves as a source of energy for the growth and development of microorganisms. Other factors being constant (climate, drainage, topography, parent material, etc.), soils rich in humus are generally more productive than those poor in humus. The high productivity of the dark-colored soils of Central United States is usually attributed to their high content of stable humus. A major problem still confronting agriculture today is the development of realistic management practices which will maintain and conserve this vital natural

Introduced Plants and Animals in the Galápagos Islands

Abstract: The Galaipagos Archipelago is a group of 14 large and numerous smaller islands, slightly more than 500 miles west of the coast of Ecuador (Fig. 1). They are volcanic in origin, and even today display the forces which created them. The islands that comprise the archipelago are geologically young. Dalrymple and Cox (1968) cite statistics which suggest that volcanism may have begun no more than two and a half million years ago. The island contain distinctive fauna and flora. Wiggins and Porter (1971) state that 32.5 percent of the vascular flora is endemic to the archipelago. The fauna also is unique, both in endemism and representative groups. Man has done much to alter the

Mycorrhiza: The Ultimate in Reciprocal Parasitism?

Abstract: Terrestrial plants are dependent upon the intense biological activity that surrounds their root systems. In the rhizosphere, micro-organisms are an integral part of numerous physiological interactions that range from saprophytism to various degrees of parasitism. Playing a dominant role among these are mycorrhizal relationships. Mycorrhizae are symbiotic associations in which the smallest order of

Antibiotics in Animal Feeds and Animal Production

Abstract: Antibiotics were introduced into animal feeds about 20 years ago when it was found that growth of young farm animals was improved and disease could be prevented or alleviated by this procedure. Within the past few years, however, bacteriologists have feared that the widespread use of antibiotics, including farm use, may foster the spread of antibiotic resistance in certain pathogenic micro-organisms. The allocation of cause between human clinical use and agricultural practice for the spread of resistance is the nub of the matter. The theory that animal feeds are a significant in resistance to disease has had a powerful influence on public attitudes in today's context of urban insouciance or hostility towards agricultural technology. Elsewhere (Jukes 1971), I have presented the thesis that such attitudes evolve from an abundant food supply, which creates the setting for the development of introspective apprehensions among the well fed. A movement against the use of antibiotics in animal feeds has been in progress for about 5 years, centered on the proposals that this use spreads transferable resistance, and thus endangers public health. The proposals are usually buttressed by the following lines of evidence: (a) the introduction of episomally-carried multiple resistance into Shigella in Japan about 10 years ago; (b) an outbreak of virulent resistant salmonellosis in England in 1965, caused by malpractice in handling calves; and (c) an increase in gram-negative, resistance infections, such as Klebsiella, in a Boston Hospital. Only the outbreak of salmonellosis in 1965 is related directly to farm livestock, and chloramphenicol, which is used against Salmonella, is not added to animal feeds. The emergence of predominantly antibiotic-tolerant bacterial flora in the intestines of animals receiving antibiotic-supplemented feeds is axiomatic, and was described 20 years ago (for references, see Jukes 1955). The point at issue is the effect of this flora on public health, and the users f antibiotic feeds have the difficult assignment of "proving a negative." In this review, I present a brief history of the use of antibiotics in animal feeds; its efficacy, utility, and safety; the nature of the "antibiotic growth response"; a short discussion of the etiology of infectious resistance; and some speculation as to the reasons for the continued effectiveness of antibiotics in animal feeds.

Lead in a Connecticut Salt Marsh

Abstract: A preliminary investigation of the horizontal and vertical distribution of lead in a Connecticut marsh was conducted in order to examine the possibility of salt marshes serving as sinks for heavy metals. Horizontal and vertical gradients in lead concentration were measured. Lead concentrations in the surface samples ranged from 9 to 190 ppm (mean 96 ppm, coef. of variation 31%) and in the 1 m samples from 3 to 123 ppm (mean 23 ppm, coef. of variation 96%). The sources of this lead contamination are presented. The author concluded that salt marshes are effective in removing lead from inflowing waters from urban centers and that this lead is accumulating in the marsh. Preliminary analyses of the first water to run off adjacent highways following the onset of a storm showed concentrations of between 1 and 14 ppm lead.

The Molecular Principles of Biological Membrane Construction and Function

Abstract: In this journal Vanderkooi and Green (1970a) have recently reviewed the basic concepts underlying the structure of biological membranes and have formally developed the protein crystal model of the membrane as a logical marriage of the unit membrane model of Danielli and Davson (1935) and of Robertson (1960) with the repeating unit model of Green and Perdue (1966). The essence of the protein crystal model is the notion of bimodal proteins in the membrane continuum, and of the packing of bimodal proteins with bimodal lipid (all other lipids may be considered to be part of the hydrophobic sector of the bimodal lipid domain). In the present review we have attempted to show how the bimodal principle of membrane construction not only organizes a vast body of experimental information about membrane proteins but unifies a wide variety of biological phenomena involving membrane systems.

The Role of Overpopulation and Agricultural Methods in the Destruction of Tropical Ecosystems

Abstract: now facing biologists is the rapid increase in the rate of destruction of tropical biota and the realization that we will probably not be able to study even a small portion of it before it is destroyed. The geometrical growth rate of the human populations of tropical countries, which were in the past largely underpopulated except in coastal areas, now threatens to destroy most natural populations of plants and animals (Kostermans, 1960; Bennett, 1968; World Population Data Sheet, June 1971). Some of these are endemic species which will be lost to science altogether (Lewis, 1970). It is believed by some experts that the tropical rain forest will all but disappear by the turn of the century (Richards, 1952). In my opinion this is an over-optimistic prediction. My travels in tropical areas of Central America and in the Amazon Basin lead me to believe that the current disturbance by man throughout much of the tropics has already dealt these delicate ecosystems a serious blow. In the Republic of Panama, the area with which I am most familiar, the situation is particularly acute. Until recent years large areas of the country, particularly the Atlantic coast and much of the eastern part of the country in the province of Darien, were sparcely inhabited (Atlas de Panama, 1965). Now large parts of these previously pristine areas have been destroyed or are in danger of being destroyed (Porter, 1970). In the past 4 years I have made trips into all provinces of Panama and have had the opportunity to fly over much of the area under discussion. It has been

Possible Biological Consequences of Plate Tectonics

Abstract: Geology is currently undergoing an upheaval as profound as Darwin's reorganization of biology in the Nineteenth Century. The purpose of this essay is to examine briefly the interface between these two sciences with an eye toward new possibilities of synthesis and new ways of viewing the parent subject, natural history. A current research trend, now accelerating in activity but still inadequately pursued, deals with the biological consequences of the geological evolution of the earth as deduced from recent theoretical ad-

Zoos: Valuable Adjuncts for Instruction and Research in Primate Behavior

Abstract: In another BioScience article (Rumbaugh, 1971), I have discussed the value of zoos for instruction in animal behavior and how arrangements and plans might be made for their use in instruction. In the present article the specific use of zoos' primate collections will be considered for instruction, for student project work, and for research projects by faculty. While it is usually the case that a zoo's prime function is the exhibiting of living animal forms for the pleasure of the public at large, its collections also should be developed as educational and research resources. In particular, zoos should be used extensively as specialized laboratories for a variety of behavioral study programs. It is a mistake to conclude, as many have done in the past, that all behavior of captive animals is bizarre, distorted, and hence worthless as material to understand scien-

Island Biology: We've Only Just Begun

Abstract: later. Others might welcome the opportunity to work on island areas. I would ask those others, "Are you going to inflict the narrowness of your declared area of specialization on insular biotas, or are you willing to let islands open your insights so that you can ask new questions, solve new problems, and indulge in personal growth as well?" I don't mean to sound sarcastic; I only mean that many discoveries yet to be made on islands cannot be predicted, and are made by the open-minded biologist. One example that comes to mind is the Darwin's Finches and the history of their study. We know that Darwin reported on them in the Journal of Researches of the Beagle voyage. About 80 years and several major expeditions elapsed between Darwin's visit and that of David Lack. One might wonder why so much time had to elapse before David Lack's (1947) classic book, which adds so much to our knowledge of these birds. I would guess that Lack on the Galapagos was a keen and imaginative observer, who did not have preoccupations about what he ought to find or what methods he should use. Rather, he merely tried to find out all he could about the Darwin's Finches. Even so, more remained for workers such as Robert I. Bowman to uncover and

Intensified Pest Management Needs of Developing Nations

Abstract: Only a few years ago many noted agriculturists and demographers were predicting world famine within this decade or the next because they were convinced that the race between food production and population was being lost (Paddock, 1967; Revelle, 1968). The world has witnessed an amazing turnabout! Tremendous food production gains have occurred in many of the developing nations within the past few years. This widely publicized phenomenon has been termed the "green revolution." It has resulted from a combina-