共查询到20条相似文献,搜索用时 15 毫秒
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Leo Hellerman 《Biology & philosophy》2006,21(4):537-552
The living forms represented in this paper are sets of parts that spontaneously increase in organization. Their organizations are measured by an information-theoretic function derived from the work of Boltzmann and Shannon. We briefly review its derivation in the context of the troubled role of mathematics in biology, and then define the function. We illustrate its nature by measuring the 22 different organizations of a set of eight things; and we facilitate its use by defining the parameters that determine an amount of organization. The measure is then applied to show that the organization of limb pairs on free-living arthropods, based on data given by Cisne, confirms a pattern of increasing organization in their evolution from the Cambrian era to the present. Further applications measure the changes in organizations of ideal (theoretical) life forms, and contrasting changes in inanimate systems. Our main results represent the reproduction of unicellular organisms, and the formation of hierarchies, as processes of increasing organization. 相似文献
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Dynamic pictures of living genomes are now beginning to emerge from systematic studies of gene expression patterns using DNA microarrays. The rich information represented in the variation in each gene's expression provides the basis for a new kind of genomic map. 相似文献
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Understanding living clathrin-coated pits 总被引:3,自引:3,他引:0
Most knowledge of clathrin-mediated endocytosis has been gained by biochemical fractionation and in vitro assays. Recently, the study of endocytosis has extended into the living cell. The tracking of individual clathrin-coated pits and vesicles (CCPs and CCVs) has provided new insight into understanding the dynamic nature of CCPs. The use of total internal reflection fluorescence microscopy (TIR-FM), also termed evanescent field microscopy, has enabled the direct observation of events occurring within a restricted area of the cell adjacent to and including the adherent plasma membrane. TIR-FM is now actively being pursued in the study of endocytic processes. The direct observation of CCP-associated proteins including clathrin itself, dynamin and, most recently, AP-2 has considerably challenged old models, confirming some points but raising very interesting new questions. 相似文献
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Inside a living cell 总被引:15,自引:0,他引:15
D S Goodsell 《Trends in biochemical sciences》1991,16(6):203-206
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Family living among birds 总被引:1,自引:0,他引:1
Jan Ekman 《Journal of avian biology》2006,37(4):289-298
Family cohesion in birds is often explained as a product of limitations on breeding opportunities leading to delayed dispersal among the offspring. Yet, it is not independent reproduction but floating (queuing outside the natal territory for a breeding opportunity) that is the alternative to delaying dispersal. In contrast to a strong phylogenetic bias in cooperative breeding that has been taken to indicate a hard-wired behaviour maintained by evolutionary inertia, offspring behaviour is plastic and facultative in group living in the short term, indicating that family cohesion is under selection. Non-breeding offspring could gain inclusive fitness that would promote family cohesion from delaying dispersal and providing alloparental care to subsequent broods to boost group productivity. This holds in particular for offspring hatched from early broods in multi-brooded species that have the opportunity to gain inclusive fitness from help in rearing siblings hatched from later broods in the same season. Yet, seasonality will circumscribe the potential for alloparenting to be the immediate factor selecting for family cohesion. The option of gaining inclusive fitness from providing alloparental care is not open to the offspring among single-brooded species until after they have survived a non-breeding season, rather indicating kin cooperation returning enhanced survival prospects from general group living effects as a more immediate factor selecting for family cohesion. Indeed, a variety of family groups maintained in the absence of alloparental care underlines the capacity of general group living enhancing survival as a primary agent selecting for family cohesion. These seasonal constraints on fitness components selecting for family cohesion may contribute to the large scale geographical pattern with a relative paucity of family cohesions among bird species in the northern hemisphere. 相似文献
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