首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
Edwin Grant Conklin, renowned US embryologist and evolutionary popularizer, publicly advocated a social vision of evolution that intertwined science and modernist Protestant theology in the early 1920s. The moral prestige of professional science in American culture — along with Conklin’s own elite scientific status — diverted attention from the frequency with which his work crossed boundaries between natural science, religion and philosophy. Writing for broad audiences, Conklin was one of the most significant of the religious and modernist biological scientists whose rhetoric went well beyond simply claiming that certain kinds of religion were amenable to evolutionary science; he instead incorporated religion itself into evolution's broadest workings. A sampling of Conklin's widely-resonant discourse suggests that there was substantially more to the religion-evolution story in the 1920s US than many creationist-centred narratives of the era imply.  相似文献   

2.
3.
Optimization of energy use by evolving organisms, predicted by theoretical extensions of the neo-Darwinian theory, i. contrasted with that of irreversible thermodynamics, which predicts an increase in orderliness and thus an increase in energy consumption per unit of biomass. We compared this index with estimates of social complexity among ant genera and species. Our results show that simple optimization models cannot explain experimental data, and that social complexity correlates differently with negentropy at different levels of analysis. Comparing the genera among Formicidae, workers (not colonies) from genera with highly social species are less negentropic than those of socially primitive ones. At the sub-generic level, social complexity correlated positively with negentropy among species, for major workers inAcromyrmex and for minor workers inAtta. The results illustrate the complexity of thermodynamic criteria in the study of evolution but also hint at their usefulness. In this case, they show that two different evolutionary routes to the complex Attini ant societies may exist.  相似文献   

4.
5.
6.
Zusammenfassung Die Serum-Eigenschaften eines gegen hohe Insulindosen resistenten Mäusestammes KL werden mit einem Stamm BUB verglichen, bei welchem bereits eine zehnfach kleinere Insulindosis Konvulsionen verursacht. Es handelt sich nicht um einen Serumfaktor des Stammes KL, der die Insulinresistenz bewirkt oder der den Stamm BUB schützt. Da keine Antikörper gefunden wurden, bleibt die Ursache der Resistenz unaufgeklärt.  相似文献   

7.
Directed evolution of enzymes for biocatalysis and the life sciences   总被引:5,自引:0,他引:5  
Engineering the specificity and properties of enzymes and proteins within rapid time frames has become feasible with the advent of directed evolution. In the absence of detailed structural and mechanistic information, new functions can be engineered by introducing and recombining mutations, followed by subsequent testing of each variant for the desired new function. A range of methods are available for mutagenesis, and these can be used to introduce mutations at single sites, targeted regions within a gene or randomly throughout the entire gene. In addition, a number of different methods are available to allow recombination of point mutations or blocks of sequence space with little or no homology. Currently, enzyme engineers are still learning which combinations of selection methods and techniques for mutagenesis and DNA recombination are most efficient. Moreover, deciding where to introduce mutations or where to allow recombination is actively being investigated by combining experimental and computational methods. These techniques are already being successfully used for the creation of novel proteins for biocatalysis and the life sciences.Received 8 June 2004; received after revision 22 July 2004; accepted 2 August 2004  相似文献   

8.
9.
10.
11.
12.
13.
Phage display, the presentation of (poly)peptides as fusions to capsid proteins on the surface of bacterial viruses, celebrates its 25th birthday in 2010. The technique, coupled with in vitro selection, enables rapid identification and optimization of proteins based on their structural or functional properties. In the last two decades, it has advanced tremendously and has become widely accepted by the scientific community. This by no means exhaustive review aims to inform the reader of the key modifications in phage display. Novel display formats, innovative library designs and screening strategies are discussed. I will also briefly review some recent uses of the technology to illustrate its incredible versatility.  相似文献   

14.
Summary Ficus can only reproduce if they are pollinated by mutualistic wasps that breed within the figs. Pollen-loaded wasps enter the figs when the female flowers are receptive. Several weeks later, their offspring load pollen within the fig and then emerge. As individual trees typically produce crops of synchronous figs at long intervals, the shortlived wasps have to move to another, receptive, tree. The wasp population can only survive, and hence the fig population reproduce, if there are trees fruiting all over the year. When only few trees are present within a population gaps in the flowering sequence may lead to the extinction of the local pollinator population. Two models are presented. One investigates the number of trees necessary in order to sustain a local pollinator population when the tree population has a seasonal pattern of fruiting. The second model investigates how such a seasonal pattern may evolve within a fig population as a result of individual selection on the trees. It is shown that pollinator populations are fragilized under seasonal conditions. Hence, the breeding system ofFicus limits their expansion into highly seasonal habitats. Seasonal habitats may also lead to seasonal adjustment of male versus female investments and to the evolution of dioecy.  相似文献   

15.
This article analyses the Danish 1909 celebrations of the centenary of Charles Darwin's birth on 12 February 1809. I argue that the 1909 meetings, lectures and publications devoted to Darwin and his theory of evolution by natural selection can be characterised by ambivalence: on the one hand, tribute to a great man of science who established a new view of nature and, on the other hand, scepticism towards the Darwinian mechanism of natural selection and the wider religious and political implications drawn from his theory. The article examines both professional and popular commemorative activities, focusing primarily on celebratory articles carried in widely circulated magazines and newspapers. I identify three types of interpretations of Darwin's ideas which I characterise as ‘radical’, ‘evangelical’ and ‘safe’ science. These different positions were closely linked to the political and cultural divisions of the periodical press. Moreover, my analysis of the popular press offers a solid basis for asserting that to most people Darwinism was associated with human evolution, primarily the relationship between man and apes, while more sophisticated discussions about the crisis of Darwinism prominent among naturalists played only a secondary role in the public arena. This article demonstrates the value of using newspapers as historical sources when looking for public images of Darwin, popular receptions of Darwinism and representations of science in general.  相似文献   

16.
This article analyses the Danish 1909 celebrations of the centenary of Charles Darwin's birth on 12 February 1809. I argue that the 1909 meetings, lectures and publications devoted to Darwin and his theory of evolution by natural selection can be characterised by ambivalence: on the one hand, tribute to a great man of science who established a new view of nature and, on the other hand, scepticism towards the Darwinian mechanism of natural selection and the wider religious and political implications drawn from his theory. The article examines both professional and popular commemorative activities, focusing primarily on celebratory articles carried in widely circulated magazines and newspapers. I identify three types of interpretations of Darwin's ideas which I characterise as 'radical', 'evangelical' and 'safe' science. These different positions were closely linked to the political and cultural divisions of the periodical press. Moreover, my analysis of the popular press offers a solid basis for asserting that to most people Darwinism was associated with human evolution, primarily the relationship between man and apes, while more sophisticated discussions about the crisis of Darwinism prominent among naturalists played only a secondary role in the public arena. This article demonstrates the value of using newspapers as historical sources when looking for public images of Darwin, popular receptions of Darwinism and representations of science in general.  相似文献   

17.
18.
Cadherins are glycoproteins that are responsible for homophilic, Ca2+-dependent cell-cell adhesion and play crucial roles in many cellular adhesion processes ranging from embryogenesis to the formation of neuronal circuits in the central nervous system. Many different experimental approaches have been used to unravel the molecular basis for cadherin-mediated adhesion. In particular, several high-resolution structures have provided models for cadherin-cadherin interactions that are illuminative in many respects yet contradictory in others. This review gives an overview of the structural studies of cadherins over the past decade while focusing on recent developments that reconcile some of the earlier findings.Received 7 January 2004; received after revision 24 February 2004; accepted 4 March 2004  相似文献   

19.
Summary The leaves on a coconut crown are arranged in 5 spirals, all running clockwise in one palm, and counterclockwise in another. The 2 types of palms in any plantation are distributed more or less equally. Data on the foliar spirality of the progeny obtained by different kinds of parental matings clearly show that the direction of foliar spiral in the coconut is not genetically determined. Additional data presented on 7860 palms show that the left-spiralled ones are in excess of the right-handeds.We thank Ir. Hasman Asiz, LPTI, for the facilities and encouragement received for completing this work, and Prof. T. Antony Davis, UNDP/FAO Coconut Agronomist, for the technical guidance in this investigation.  相似文献   

20.
Homing endonucleases: structure, function and evolution   总被引:19,自引:0,他引:19  
‘Homing’ is the lateral transfer of an intervening genetic sequence, either an intron or an intein, to a cognate allele that lacks that element. The end result of homing is the duplication of the intervening sequence. The process is initiated by site-specific endonucleases that are encoded by open reading frames within the mobile elements. Several features of these proteins make them attractive subjects for structural and functional studies. First, these endonucleases, while unique, may be contrasted with a variety of enzymes involved in nucleic acid strand breakage and rearrangement, particularly restriction endonucleases. Second, because they are encoded within the intervening sequence, there are interesting limitations on the position and length of their open reading frames, and therefore on their structures. Third, these enzymes display a unique strategy of flexible recognition of very long DNA target sites. This strategy allows these sequences to minimize nonspecific cleavage within the host genome, while maximizing the ability of the endonuclease to cleave closely related variants of the homing site. Recent studies explain a great deal about the biochemical and genetic mechanisms of homing, and also about the structure and function of several representative members of the homing endonuclease families. Received 6 January 1999; received after revision 24 February 1999; accepted 24 February 1999  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号