摘要:

Summary1. The gene mutations and the chromosomal changes obtained inDrosophilaunder laboratory conditions have their counterparts also in free‐living populations. The fact that individuals ofDrosophilafound in nature are as a rule homogeneous and only rarely show striking variations is due to the majority of the mutants concealed in them being recessive to the normal or “wild‐type” condition.2. The concealed mutants can be detected either by inbreeding the offspring of wild individuals, or by more complex but more accurate genetic techniques that result in obtaining specimens homozygous for a given “wild” chromosome. As expected, the data obtained with the aid of either method are essentially similar.3. InD. melanogasterthe autosomes contain not only mutants producing visible external effects but also many recessive lethals. The kind and the frequency of the mutants found is variable from population to population and from year to year.4. In free‐living populations ofD. pseudoobscuruthe third chromosome, and probably other autosomes as well, are infested with lethals, semi‐lethals, deleterious viability modifiers, modifiers of the development rate, visible mutants, and other genetic changes. Again, both the quality and the quantity of these changes vary from population to population.5. Knowing the frequency of allelic lethals within a population, one can compute the rate at which they must be eliminated by natural selection. This rate can be compared to that of the origin of new lethals by mutation. Theoretically, the two rates must be alike in populations at equilibrium. Actually, the supposed elimination rate is smaller than the corresponding mutation rate. This may be due either to some of the lethals not being fully recessive, or else to the population size being subject to sharp seasonal fluctuations.6. Inversions of chromosome segments are extremely common in free‐living populations of all species ofDrosophilaso far studied in this respect. Certain kinds of multiple inversions make it possible to establish the phylogenetic relationships of the chromosome structures involved.7. InD. pseudoobscura, D. aztecaand probably in many other species each of the different structural types of the chromosomes occurs in a definite geographical region, thus giving rise to chromosomal races.8. Aside from the above “macrogeographic” variability, there exist also differences, usually of a quantitative nature, between populations inhabiting neighbouring or even contiguous localities. Moreover, the genetic composition of a population does not remain constant from year to year. This “micro‐geographic” variability is probably due to a restriction of the effective size of the breeding population in most species ofDrosophila.9. A species ofZhosophiladoes not represent a single panmictic population, but rather a mass of local colonies that are able to pursue, within limits, different evolutionary courses. The fate of a colony is, of course, controlled by natural selection, yet selection is not the sole determiner of the population dynamics. As predicted on theoretical grounds by Wright (1931, 1932), shifts in the genetic composition of a population may be due to the limitation of its

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1939.tb00847.x

出版商:Blackwell Publishing Ltd    

年代:1939

数据来源: WILEY

摘要:

ZusammenfassungDie vorliegende Untersuchung dient der Klärung terminologischer und methodischer Fragen der Tiersoziologie. Sie berücksichtigt hauptsächlich die Kleintierbestände der Landtiergesellschaften.In einer Übersicht über die einschlägige Literatur wird nachgewiesen, dass die Tiersoziologie bisher einer einheitlichen Terminologie und klarer Ziele entbehrt. Die Biocönose erweist sich als Grundeinheit für die Einteilung und Klassifikation der Tiergesellschaften als unbrauchbar. Sie ist von den verschiedenen Autoren sehr verschieden definiert worden, jedoch niemals so, dass auf Grund ihrer Definition die Abgrenzung von Gesellschaftsindividuen und Gesellschaftstypen in der Natur mit annähernd gleicher Exaktheit durchgeführt werden könnte wie auf Grund des Assoziationsbegriffes der Botanik.Es wird daher vorgeschlagen, von nun an auch in der Tiersoziologie von der Assoziation als soziologischem Einheitsbegriff auszugehen und die Assoziation wie in der Pflanzensoziologie durch ihre Charakterarten und ihre charakteristische Artenverbindung zu kennzeichnen. Der Klarheit der Terminologie halber sind die pflanzlichen Gesellschaftseinheiten als Phytoassoziationen, die tierischen als Zooassoziationen zu bezeichnen. Der Terminus “Assoziation” bleibe den Lebens‐gemeinschaften von PflanzenundTieren vorbehalten.An einer Reihe von Beispielen wird nachgewiesen, dass es auch in den Tiergesellschaften allenthalben Charakterarten gibt, die sich durch einen hohen Grad von Gesellschaftstreue und Gesellschaftsstetigkeit auszeichnen; es ist daher auch im Bereiche der Tierwelt überall möglich, Assoziationen zu erkennen und gegeneinander abzugrenzen.Für die tiersoziologische Aufnahmspraxis und die Beschreibung der Assoziationen werden in enger Anlehnung an die Pflanzensoziologie Vorschläge erstattet, nachdem untersucht worden ist, inwieweit die pflanzensoziologischen Untersuchungsmethoden auch in der Tiersoziologie Anwendung finden können. Die Bestandesanalyse hat auf tiersoziologischem Gebiete durch annähernd quantitative Aufnahme der in einheitlichen Probeflächen von gleicher Grösse vorhandenen Tiere zu geschehen. Fur die Ermittlung des Arthropodenbestandes sind Flächen von mindestens I m2notwendig.Für die Chakterisierung der Assoziationstypen ist in der Tiersoziologie wie in der Pflanzensoziologie die Ermittlung der Charakterarten und der charakteristischen Artenverbindung erforderlich. Von Charakterarten ist in erster Linie ein hoher Grad von Gesellschaftstreue und Gesellschaftsstetigkeit zu fordern, das dominante Auftreten einer Charakterart in der zu kennzeichnenden Assoziation ist aber jeweils mit zu berücksichtigen.SummaryThe present study deals with questions of terminology and method in animal ecology, particularly regarding communities of smaller land animals.From a consideration of the literature it is evident that up to the present animal ecology has lacked both a uniform terminology and clear aims. The concept of biocoenosis turns out to be useless as a unit for the subdivision and classification of animal communities. It has been defined in quite different fashions by different authors, and never in such a way that it could be used, as the association concept is used in botany, for the exact delimitation of individual animal communities and types of animal community in nature.It is therefore now proposed to make use of the association as the sociological unit in animal as well as plant ecology, and to define the association, as is done in botany, by its characteristic species and groups of species. For the sake of clarity, plant ecological units should be termed phytoassociations, animal units zooassociations, the word “association” being reserved for groups of both animals and plants.By a series of examples it is shown that characteristic species with a high degree of ecological stability are to be found everywhere in animal just as in plant communities; it is therefore possible to recognize associations everywhere in the animal world, and to delimit them from one another.After an investigation of the extent to which the methods of plant ecology are applicable to animal communities, methods closely following botanical practice are proposed for the purpose of making animal ecological surveys and for the description of associations. The analysis of populations in animal ecology should be carried out by an approximately quantitative census of the animals present in sample areas of equal dimensions.In defining types of associations, the determination of characteristic species and groups of species is essential in animal ecology just as in plant ecology. A characteristic species must exhibit a high degree of ecoIogicaI constancy. The dominant presence of a characteristic s

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1939.tb00848.x

出版商:Blackwell Publishing Ltd    

年代:1939

数据来源: WILEY

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1939.tb00849.x

出版商:Blackwell Publishing Ltd    

年代:1939

数据来源: WILEY

摘要:

SummaryAdenine derivatives represent a group of substances of considerable biological interest. Our knowledge of their occurrence in nature, properties and role is derived from both chemical and biological investigations.With regard to chemical structure, they fall into three groups of different complexity: (I) the comparatively simple molecules adenosine, adenylic acid, adenyl pyrophosphoric acid, (2) the intermediate compounds di‐adenosine‐penta‐phosphoric and di‐adenosine‐tetraphosphoric acid, and (3) the dinucleotides cozy‐mase, Warburg's coenzyme, amino‐acid oxidase coenzyme, which apart from adenine possess yet another base (pyridine, alloxazine).Adenosine does not occur in free state in nature. It can be obtained by hydrolysis from yeast nucleic acid. Adenosine is a substance of potent physiological activity, especially on the heart. Deamination of adenosine to inosine (e.g. by enzymes present in many tissues and body fluids) renders this substance phydogically inactive.Adenylic acid (adenine nucleotide) is a general cell constituent. With regard to chemical structure we distinguish between muscle and yeast adenylic acid, the phosphoric group in the former being attached to C5, in the latter toC3, of the ribose molecule. Accordingly these two substances differ in several aspects, both chemical and biological. It is the muscle adenylic structure which is met with in the rest of the higher adenine derivatives.Adenylic acid occurs in tissues and cells in the form of adenyl pyrophosphoric acid and only seldom in free state (heart muscle). The pyrophosphoric group is easily split off, enzymically or by acid hydrolysis. A method is described for quantitative determination of adenyl pyrophosphoric and adenylic acid in biological material.In addition to adenylic and adenyl pyrophosphoric acid there exist other poly‐phosphoric adenine derivatives, such as the di‐adenosine‐pentaphosphoric acid in heart muscle and the di‐adenosine‐tetraphosphoric acid in yeast.Cozymase, diphosphopyridine nucleotide, originally called “coenzyme of alcoholic fermentation”, is a substance of wide distribution in nature. Owing to the presence of the pyridine ring (nicotinic acid amide) in its molecule, it can undergo reversible oxidation and reduction: cozymasezdihydrocozymase. In the enzymic oxido‐reduction systems (dehydrogenases) where it acts as coenzyme it plays the part of a hydrogen carrier, transferring the hydrogen from the substrate to a hydrogen acceptor such as flavoprotein.Warburg's coenzyme, triphosphopyridine nucleotide, was first isolated from red blood cells and later found to occur in many other cells. Structurally it is closely related to cozymase, but it possesses one more phosphoric acid group than cozymase. The mechanism of its action as hydrogen carrier in enzyme systems is identical to that of cozymase, but in purified enzyme preparations these two coen‐zymes cannot replace each other in spite of their close similarity. There is some evidence, however, that cozymase and Warburg's coenzyme are to a certain degree interconvertibIe under the influence of cell extracts.Alloxazine‐adenine nucleotide is a substance of ubiquitous presence in biological material. Originally isolated from heart muscle and kidney as the coenzyme of the amino‐acid oxidase, it was soon found to be essential for other enzymic proteins as well (flavoprotein, xanthine oxidase). Its role as hydrogen carrier is due to the reversible oxidation and reduction of the alloxazine ring.The function of the adenine derivatives in biological processes, e.g. phosphate transfer by the adenylic system and hydrogen transfer by cozymase, is discussed in muscle glycolysis and alcoholic fermentation. Coupling is shown to occur between the phosphorylations and oxido‐reductions in some of the intermediary stages of glycolysis and fermentation.Enzyme systems are quoted in which the two pyridine dinucleotides and the all

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1939.tb00850.x

出版商:Blackwell Publishing Ltd    

年代:1939

数据来源: WILEY

摘要:

Summary1. The application of stable isotopes as indicators does not differ in principle from the application of radioactive isotopes, though the determination of the latter is generally more convenient.2. Since deuterium has several physical properties which are markedly different from those of the more abundant isotope of hydrogen it has definite biological effects in high concentrations. In low concentrations there are no appreciable biological effects, and it is not expected therefore that the application of deuterium will be limited in this respect.3. Deuterium is used as an indicator in two ways: (a)it is used as a label directly attached to the carbon atoms of metabolites, (b) reactions are carried out in a heavy‐water medium and the uptake of deuterium in the end‐products is determined.4. An account is given of the methods for the determination of deuterium and of some of the methods for preparing deutero‐organic compounds. The deuterium content of an organic compound is generally calculated from the density of its combustion water.5. The stability of the carbon‐hydrogen bond is discussed; although it is often possible to predict the stability of this bondin vitro, it is concluded that the possible wandering of the label under biological conditions would limit its useful application to a few types of compounds, such as the relatively inert fatty acids and steroids.6. The retention time of a molecule of water in the human organism has been found to be 14 days by experiments which involved the ingestion of heavy water and the determination of the deuterium content of the urine. The permeability of frog skin to water was found to be 400 days at o° C.7. The metabolism of trideuteroacetic acid by yeast was studied. From the deuterium content of succinic acid isolated it was concluded that the acetic acid was converted into succinic acid, but the deuterium values gave no clue as to the mechanism of this conversion. The steroids isolated from the yeast had a higher deuterium content than the fatty acids, and it was concluded therefore that they were not derived from the fatty acids, but probably from the acetic acid.8. In feeding experiments with deutero‐fatty acids it was found that they were deposited before being burned, even when the fat content of the diet was abnormally low. Caproic and butyric acids were disposed of by mice within 8 hr., and this disposal did not consist of a conversion into higher fatty acids. From the deuterium content of lipoids and glycerides isolated after the feeding of deutero‐fat it was concluded that ingested fatty acids play an active part in the metabolism of these compounds. The source of increased liver fat which results from starvation, exposure to carbon tetrachloride vapours, and injection of an extract of the anterior pituitary gland, was traced to the depot fat, and it was also concluded that this is not the source of increased liver fat resulting from a high carbohydrate diet. Desatura‐tion and saturation of fatty acids were proved to take place by following the deuterium content of the unsaturated fatty acids of mice which had been fed saturated deutero‐fatty acids, and vice versa. It was shown that stearic acid is converted by the organism into palmitic acid.9. It was shown that cholestenone and coprostanone are converted by the dog and by man into coprosterol. These two substances can be intermediates in the conversion of cholesterol into coprosterolin oitro.10. When yeast was grown in a heavy‐water medium on various nutrient hexoses it was found that the least deuterium was incorporated in the glycogen subsequently isolated when the nutrient hexose was fructose. It was accordingly concluded that the most direct conversion of a hexose to glycogen was from fructose, and not from glucose. The deuterium values did not give a satisfactory clue to the mechanism of this conversion.11. From the deuterium content of the muscle of a mouse injected with heavy water the myosin content was calculated to be 55 %. In experiments of long duration a considerable amount of deuterium was built into the protein of mice, but no conclusions were drawn from the results. A series of deuteroamino acids were isolated from mice which had been maintained with an artificially raised level of heavy water in their body fluids. No deuterium was found in the indispensable amino acid, lysine.12. Attempts were made to determine the rates of biological synthesis and breakdown of fatty acids and cholesterol from the deuterium content of these compounds isolated from mice which had been kept for various periods with heavy water. The results thus obtained were not conclusive.13. Heavy nitrogen has also been used as an indicator. It was found that the nitrogenofingested ammonium salts and of ingested dl‐tyrosine was incorporated in a large number of amino acids, with the exception of lysine. In some cases this incorporation was shown to take place by a process of deamination and reamination. It was shown that the glycine of urinary hippuric acid is not all derived from ingested glycine, even when a superfluous amount is fed.14. The heavy isotope of oxygen has been used in a study of the source of the oxygen of respiratory carbon dioxide.15. The possibilities of the application of the heavy isotope of

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1939.tb00851.x

出版商:Blackwell Publishing Ltd    

年代:1939

数据来源: WILEY