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1.
Although the term ‘emergence’ has received wide attention in the literature, most of this attention has been focused on epistemological discussions about the nature of what might be considered emergent behavior in self-organizing systems. For the concept of emergence to have any great utility for biologists, it must (1) be perceptible as a physical, quantitative property rather than just a philosophical one; (2) have a quantitative definition applicable to all levels of biological organization; and (3) be an essential component of biological system performance or evolution. Using an independent, cellular population model (running in the StarLogo system), we have developed a mutual information calculation to measure the information expansion when considering the interactions between a population of herbivores and an environment in comparison to the interactions between the individual herbivores and that environment. In self-organizing biological systems, the collective action of massively parallel units generates a greater potential complexity in the information processing capacity of the ‘whole’ system relative to the ‘individual’ parts, and as such, there is a demonstrable increase in mutual information content. From this perspective, we consider emergence to exist as a simple information expansion that is a default behavior of any system with multiple, component parts governed by a simple, probabilistic rule set. It is not a first principle of self-organizing biological systems, but rather a collective behavior that can be quantitatively described in practical terms for experimental biologists. With a quantitative formulation, the concept of emergence may become a useful information statistic in assessing the structure of biological systems.  相似文献   

2.
The majority of Middle American cichlids are placed in the informal assemblage ‘Cichlasoma.’ The group is divided into eight sections which appear to be based primarily on trophic morphology. Although several members of ‘Cichlasoma’ have been used in ecomorphological, behavioral, and biogeographic studies, no phylogenetic hypotheses for the group exist. In an attempt to develop a better understanding of the phylogenetic relationships of ‘cichlasomine’ cichlids, we examined the evolution of the trophic specialization, substratum-sifting, in two sections, ‘Cichlasoma(Thorichthys)’ and ‘C.(Amphilophus),’ to determine whether the trait reflects common ancestry. We sequenced the complete mitochondrial cytochromebgene for 19 cichlids representing six sections of ‘Cichlasoma,’ and representatives of other Neotropical Cichlidae. Additional cichlid, and noncichlid outgroup sequences were included for a total of 22 taxa. The molecular phylogeny supports the recognition of the section ‘C.(Thoricthys)’ as a natural group, and we place those cichlids in the genusThorichthys.The phylogeny also depicts ‘C.(Amphilophus)’ as paraphyletic, with substratum-sifters and generalized predators forming separate nonsister clades. We recommend that the substratum-sifting clade of the section ‘C.(Amphilophus)’ be placed in the resurrected genusAstatheros.The generalized predator clade of ‘C.(Amphilophus)’ contains only two species, ‘C. (A.) citrinellum’ and ‘C. (A.) labiatum,’ which we place in the genusAmphilophus.The phylogenetic hypotheses generated indicate that the substratum-sifting generaThorichthysandAmphilophusdo not share a common ancestor. Reconstruction of the evolution of substratum-sifting is equivocal, requiring either the independent evolution of the trait on two separate occasions or its presence in a more inclusive clade and subsequent loss in nonsubstratum sifting species.  相似文献   

3.
4.
Natural revegetation on topsoiled mining-spoils according to the exposure   总被引:1,自引:0,他引:1  
Comparative plant successional studies on derelict sites are providing significant insights into vegetation dynamics to ensure the success of future revegetation projects in these areas and, in the short-term, by using a space-for-time substitution. In this paper we describe, in relation to site exposure, vegetation development on waste rock materials covered with biologically active soil media, and compare this development with that from a previous study at the same mine (CW Spain) on non-biologically modified waste rock materials. The succession under study is faster on the North slope, as expected, and does not differ significantly from the general pattern of primary revegetation, although it was characterised by its own sequence of plant species. The topsoiling of waste increases richness and diversity from the first year of revegetation, reduces the time required for recovery of a terminal stage, and highlights the influence of slope orientation on vegetation dynamics. A total of 237 plant taxa were recorded, showing one of four patterns of change: (1) ‘pioneer’, (2) ‘intermediate’, (3) ‘late coloniser’ and (4) ‘fluctuating’.  相似文献   

5.
Symbiotic algae incubated in host tissue homogenate of the coral Plesiastrea versipora for 2 h in the light released at least four and a half times as much photosynthetically fixed carbon (range 13.8±3.1 to 158±9.5 nmol C/106 algae) as algae incubated in seawater (range 1.4±0.3 to 10.8±0.6 nmol C/106 algae) indicating the presence of ‘host release factor’. When algae were incubated in a low molecular weight fraction of homogenate containing partially purified ‘host release factor’ they also released more carbon (range 62.2±3.7 to 279±11.4 nmol C/106 algae) than algae incubated in seawater. This low molecular weight fraction contained free amino acids. We tested the hypothesis that the free amino acids in this fraction were responsible for ‘host release factor’ activity. Algae incubated in a mixture of free amino acids equivalent to those found in this fraction, released more fixed carbon (range 2.4±0.3 to 25.2±0.2 nmol C/106 algae) than algae incubated in seawater but in each experiment, release was much lower than when algae were incubated in host tissue homogenate. These data indicate that the stimulation of release of photosynthetically fixed carbon from the symbiotic algae of Plesiastrea versipora incubated in partially purified host release factor is not primarily due to the presence of free amino acids. We are continuing further studies to determine the exact nature of the active compound.  相似文献   

6.
Pengmin Li  Lailiang Cheng   《Plant science》2009,177(5):418-426
Pigments, chlorophyll fluorescence, dark respiration, and the antioxidant system in the shaded peel of green ‘Anjou’ pear (Pyrus communis L.) and its bud mutation, red ‘Anjou’, were compared in response to high peel temperature, high light alone or in combination to determine the protective role of anthocyanins under high temperature with or without light. Under high temperature treatment alone, no difference in the maximum quantum yield of PSII (FV/FM) was detected between red ‘Anjou’ and green ‘Anjou’; the superoxide dismutase activity and the glutathione pool were up-regulated in green ‘Anjou’ peel but remained unchanged in red ‘Anjou’ peel. Under high temperature coupled with high light, the FV/FM of green ‘Anjou’ peel was decreased to a lower value than that of red ‘Anjou’, and significant interaction was detected between temperature and light for both cultivars. Furthermore, the difference in FV/FM between red ‘Anjou’ and green ‘Anjou’ under high temperature coupled with high light was significantly larger than that under high light alone, indicating that this larger difference was caused by the interaction between high temperature and high light as no significant difference was detected in FV/FM between the two cultivars under high temperature treatment alone at any sampling point. It is concluded that the elevated anthocyanin level in the shaded peel of red ‘Anjou’ does not alter its thermotolerance in the dark, but makes it more tolerant of high temperature under high light.  相似文献   

7.
8.
The safety of biological control is a contentious issue. We suggest that constructing and analyzing food webs may be a valuable addition to standard biological control research techniques, as they offer a means of assessing the post-release safety of control agents. Using preliminary data to demonstrate the value of food webs in biocontrol programs, we quantified the extent to which a key agent has infiltrated natural communities in Australia and, potentially, impacted on non-target species. Using these data, we also demonstrate how food webs can be used to generate testable hypotheses regarding indirect interactions between introduced agents and non-target species. We developed food webs in communities invaded to varying degrees by an exotic weed, bitou bush, Chrysanthemoides monilifera ssp. rotundata, and a key biocontrol agent for this weed in Australia, the tephritid fly, Mesoclanis polana. Three food webs were constructed during springtime showing the interactions between plants, seed-feeding insects and their parasitoids. One food web was constructed in a plot of native Australian vegetation that was free of bitou bush (‘bitou-free’), another in a plot of Australian vegetation surrounded by an invasion of bitou bush (‘bitou-threatened’) and a third from a plot infested with a monoculture of bitou bush (‘bitou-infested’). The bitou-free web contained 36 species, the bitou-threatened plot 9 species and the bitou-infested web contained 6 species. One native Australian herbivore attacked the seeds of bitou bush. M. polana, a seed-feeding fly, was heavily attacked by native parasitoids, these being more abundant than the parasitoids feeding on the native seed feeders. A surprising result is that none of the three species of native parasitoids reared from M. polana were reared from any of the native herbivores. The food webs revealed how a highly host-specific biocontrol agent, such as M. polana has the potential to change community structure by increasing the abundance of native parasitoids. The webs also suggest that indirect interactions between M. polana and native non-target species are possible, these been mediated by shared parasitoids. The experiments necessary to determine the presence of these interactions are outlined.  相似文献   

9.
The mathematical model of Hung (Tsai and Hung, 1984) is empolyed to determine the wall shear rate acting on canine carotid arteries perfused in vitro. Model equations for pulsatile flow in a deformable vessel are coupled with experimental data of dynamic pressure drop, flow rate, vessel radius and radial wall motion. Derived quantities, e.g. velocity profiles and wall shear, are obtained for vessels exposed to ‘normotensive’ hemodynamics, ‘hypertension’ simulations and perfusions in which the compliance of the vessel wall is deliberately altered. Our results indicate that wall shear varies markedly as a function of the hemodynamic environment. The effects of vessel radius vs flow rate on the development of wall shear are also demonstrated. It is found that convective processes correlate with the magnitude of wall shear in the ‘hypertension’ simulations.The present findings and complementary published data may explain, at least in part, the variations in vessel wall transport and endothelial cell biology we observe as a function of the hemodynamic environment. For example we have documented that the exposure of canine carotids to ‘hypertensive’ (vs ‘normotensive’) hemodynamics is associated with an increased flux of lipoproteins (LDL) into the intima and luminal media. Alternations in wall compliance, on the other hand, profoundly influence endothelial shape, orientation and cytoskeletal array.  相似文献   

10.
Kant’s analysis of the concept of natural purpose in the Critique of judgment captured several features of organisms that he argued warranted making them the objects of a special field of study, in need of a special regulative teleological principle. By showing that organisms have to be conceived as self-organizing wholes, epigenetically built according to the idea of a whole that we must presuppose, Kant accounted for three features of organisms conflated in the biological sciences of the period: adaptation, functionality and conservation of forms. Kant’s unitary concept of natural purpose was subsequently split in two directions: first by Cuvier’s comparative anatomy, that would draw on the idea of adaptative functions as a regulative principle for understanding in reconstituting and classifying organisms; and then by Goethe’s and Geoffroy’s morphology, a science of the general transformations of living forms. However, such general transformations in nature, objects of an alleged ‘archaeology of nature’, were thought impossible by Kant in §80 of the Critique of judgment. Goethe made this ‘adventure of reason’ possible by changing the sense of ‘explanation’: scientific explanation was shifted from the investigation of the mechanical processes of generation of individual organisms to the unveiling of some ideal transformations of types instantiated by those organisms.  相似文献   

11.
This article explores the connections between eugenics, politics and the state, taking the Swiss case as a particular focus. It is argued that Switzerland provides a historical example of what Bauman [Bauman, Z. (1989). Modernity and the Holocaust. Cambridge: Polity Press.] describes as ‘gardening states’: states that are concerned with eliminating the ‘bad weeds’ from the national garden and thereby constructing sharply exclusionary national identities. The Swiss experiments with eugenics (1920s–1960s) can be seen as an example of an ongoing struggle against ‘difference’. Against this backdrop I will examine, first, the ways in which state regulation of reproductive sexuality, and other eugenic measures, became central mechanisms for dealing with cultural and other ‘differences’ in the Swiss nation. Second, I will analyse the gendered nature of such mechanisms, as well as the preoccupation with racial ‘difference’ exemplified by eugenic policies towards ‘Gypsies’. To conclude, I will examine the impact of political institutions and political ideology, in particular, social democracy, on these eugenic gardening efforts.  相似文献   

12.
Background The critical review is an important, though not always well understood and correctly applied element of Life Cycle Assessment studies. It is the intention of this paper to analyse the relevant standards and to present personal experiences in conducting critical reviews.Results and Discussion A peer review for LCA-studies was first proposed in the SETAC guidelines ‘A Code of Practice’ (1993). The ISO standard 14040 (1997) describes three types of ‘Critical review’ which are optional in general, but mandatory ‘for LCA studies used to make a comparative assertion that is disclosed to the public’. For this purpose, the most comprehensive form according to section 7.3.3, the panel method, has to be (‘shall’ in ISO terminology) be used. From personal experience, this method is found to be the most frequently performed in practice (60%), the average panel size being three experts. Large panels with more than 4 experts are rare.Recommendation Personal experience leads to supporting the recommendation by SETAC of the accompanying or ‘interactive’ critical review, which should be preferred, over the review ‘a posteriori’, which offers considerable risks in regards to the duration and costs of an LCA study. ISO 14040, on the other hand, does not recommend one or the other way of performing the critical review.  相似文献   

13.
In the filamentous fungus Podospora anserina, many pigmentation mutations map to the median region of the complex locus ‘14’, called segment ‘29’. The data presented in this paper show that segment 29 corresponds to a gene encoding a polyketide synthase, designated PaPKS1, and identifies two mutations that completely or partially abolish the activity of the PaPKS1 polypeptide. We present evidence that the P. anserina green pigment is a (DHN)-melanin. Using the powerful genetic system of PaPKS1 cloning, we demonstrate that in P. anserina trans-duplicated sequences are subject to the RIP process as previously demonstrated for the cis-duplicated regions.  相似文献   

14.
Two alphaproteobacterial Neisser negative ‘Nostocoida limicola’ morphotypes differing slightly in their trichome diameter and filament regularity were dominant populations in the Bendigo, Victoria, Australia activated sludge community removing phosphorus (P). Neither responded to the FISH probes available for any of the other alphaproteobacterial ‘N. limicola’ morphotypes. Instead both fluoresced with the DF988 FISH probe designed originally to target alphaproteobacterial cluster II Defluviicoccus tetrad forming organisms. A 16S rRNA based clone library from this biomass revealed that the alphaproteobacterial clones grouped closely with CandidatusMonilibacter batavus’ and Defluviicoccus clones in a cluster separate from the existing cluster I and II Defluviicoccus. When a FISH probe was designed against these, it only hybridized to the thinner and less abundant ‘N. limicola’ morphotype. Micromanipulation–RT-PCR was used to selectively recover the main ‘N. limicola’ morphotype and a FISH probe designed against the 16S rRNA clones generated from it showed only this filament fluoresced. From FISH based surveys, both ‘N. limicola’ variants occurred frequently in phosphorus removal activated sludge systems in Australia treating domestic waste. The data suggest that they represent two new strains of CandidatusMonilibacter’, which on this evidence are filamentous members of the genus Defluviicoccus, a potential competitor for the polyphosphate accumulating organisms in these communities.  相似文献   

15.
From the later part of the Devonian through the Permian, calcareous foraminifers became abundant and evolved rapidly. This rapid evolution of taxa forms the basis of a detailed zonation through the Carboniferous and Permian. Comparison of this evolutionary history of foraminifers, their biostratigraphic zonation, and the depositional sequences in which they occur suggests that sea-level events in late Paleozoic depositional history contributed significantly in subdividing a fairly continuous evolutionary record into a succession of about 75 identifiable foraminiferal zones during a 100–125 Myr time span. Although variable in terms of duration and vertical occurrences, the more completely recorded high-stand intervals give brief histories of the foraminiferal evolutionary record and are sandwiched between the poorly recorded or unrecorded low-stand intervals. Many of the individual foraminiferal zones are confined to a single depositional sequence.The late Paleozoic carbonate foraminiferal fossil record, as with the rest of the fossil record, is strongly affected by sediment deposition-nondeposition as a result of major changes in sea level. This incomplete fossil record is the result of repeated depositional breaks because of the way that depositional sequences form. It is not possible to ascribe macromutations, ‘punctuated’ evolution or ‘punctuated gradualism’ as the cause of this evolutionary pattern of the shelf-carbonate fossil record. This pattern is distinctive and we refer to it as ‘sequence evolution’ and ‘sequence extinction’. In the later part of the Middle Permian and in the Late Permian, the fossil record clearly illustrates that a series of faunal losses through ‘sequence extinctions’ progressively exceeded faunal replacements and new species through ‘sequence evolution’, but not a ‘mass extinction’ as is commonly ascribed to the end of the Permian Period. Most Permian faunas became extinct in the interval of 8 to 4 million years before the end of the Late Permian.  相似文献   

16.
In experiments, there are usually two general ways of obtaining dominants and subordinates to test for the effect of recent experience upon ulterior behavior and dominance. One is to ‘impose’ such an experience on the contestants by a priori deciding which individual of the pair will become the dominant and which will become the subordinate through the use of rigged contests. The second technique is to let contestants ‘self-select’ the winner and loser by waiting for the spontaneous outcome of dyadic encounters between two usually well matched opponents. These two techniques of obtaining dominants and subordinates probably represent extreme cases on a single continuum of investment made by animals to settle dominance. To test this, we compared dominants and subordinates obtained from these two techniques in Xiphophorus fish males. It was found that pairs obtained through rigged contest (R) were much more aggressive in subsequent encounters than pairs in which the dominant and subordinate could self-select (S). They recuperated more rapidly from handling, initiated contact earlier, took more time to assess each other, and fought for a longer period of time. Prior-winners and prior-losers of the R condition more frequently relied on aggressive behavior during contest than that of the S condition. As a consequence, prior-winners and prior-losers of the R condition won equally the subsequent contest. On the contrary, prior-winners of the S condition defeated their prior-loser opponent in a majority of cases. These results can be tentatively explained by the following principle, winning or losing against a well matched opponent would leave more ‘experience’ than winning over a much weaker opponent, or losing to a much stronger one. This reinforces the hypothesis that prior-experiences are not qualitative states but come in various degrees.  相似文献   

17.
The aim of this work was to investigate whether Fe reduction and antioxidant mechanisms were expressed differently in five Prunus rootstocks (‘Peach seedling,’ ‘Barrier,’ ‘Cadaman,’ ‘Saint Julien 655/2’ and ‘GF-677’). These rootstocks differ in their tolerance to Fe deficiency when grown in the absence of Fe (−Fe) or in presence of bicarbonate (supplied as 5 or 10 mM NaHCO3). Fe deficiency conditions, especially bicarbonate, were shown to decrease Fe and total chlorophyll (CHL) concentration. In the (−Fe)-treated roots of all rootstocks and in the 5 mM NaHCO3-treated ones of the tolerant ‘GF-677’ the Fe(III)-chelate reductase (FCR) activity was stimulated. On the contrary, apart from the ‘GF-677,’ FCR activity was greatly inhibited by the 10 mM NaHCO3. From the results obtained with decapitated rootstocks, it is not entirely clear whether or not the presence of shoot apex was a prerequisite to induce FCR function in all rootstocks tested. In the leaves of rootstocks exposed to the (−Fe) treatment, superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities were enhanced whereas the levels of the non-enzymatic antioxidants (FRAP values) were increased in the Fe-deprived leaves, irrespective of the rootstock. Except for ‘Peach seedling,’ foliar SOD activity was stimulated by the presence of NaHCO3. Furthermore, POD activity was increased in the ‘Saint Julien 655/2’ and ‘GF-677,’ but was depressed in the ‘Barrier’ rootstocks exposed to 10 mM NaHCO3. As a result of 10 mM NaHCO3, the expression of a Cu/Zn-SOD and a POD isoform was diminished in the leaves of ‘Peach seedling’ and ‘Barrier,’ respectively. By contrast, an additional isoform of both POD and Mn–SOD were expressed in the leaves of ‘GF-677’ exposed to 10 mM NaHCO3 suggesting that the tolerance of rootstocks to Fe deficiency is associated with induction of an antioxidant defense mechanism. Although CAT activity was increased in the 5 mM NaHCO3-treated leaves of ‘GF-677,’ specifically the 10 mM NaHCO3 treatment resulted in a decrease of CAT activity and an accumulation of H2O2, indicating that bicarbonate-induced Fe deficiency may cause more severe oxidative stress in the rootstocks, than the absence of Fe. A general link between Fe deficiency-induced oxidative stress and Fe reduction-sensing mechanism is also discussed.  相似文献   

18.
Harpellales (Legeriomycetaceae, Zygomycota) or ‘trichomycetes’ are fungi that inhabit the digestive tracts of arthropods such as insects, millipedes, and crustaceans. In the current study we examined changes in 5 morphological characters of Smittium culisetae (Harpellales: Legeriomycetaceae) between the two dipteran (mosquito, black fly) hosts reared under 3 different temperatures (17, 22, 30 °C). Both host and temperature had a pervasive effect on the linear dimension of trichospores, their generative cells and hyphae width. At 30 °C the mean size of all 5 morphological characters were consistently larger in fungus taken from the mosquito host than from the black fly host. At 17 °C and 22 °C, however, there were no consistent patterns. The effect of host was so pronounced that it could be accurately determined which host S. culisetae colonised based on differences in linear morphology. Such changes in fungal morphology between hosts have important ramifications for the morphologically based taxonomy of this group.  相似文献   

19.
Virtual reality (VR) has become mature enough to be successfully used in clinical applications such as exposure therapy, pain distraction, and neuropsychological assessment. However, we now need to go beyond the outcome data from this research and conduct the detailed scientific investigations required to better understand what factors influence why VR works (or doesn’t) in these types of clinical applications. This knowledge is required to guide the development of VR applications in the key areas of education, training, and rehabilitation and to further evolve existing VR approaches. One of the primary assets obtained with the use of VR is the ability to simulate the complexity of real world environments, within which human performance can be tested and trained. But this asset comes with a price in terms of the capture, quantification and analysis of large, multivariate and concurrent data sources that reflect the naturalistic behavioral interaction that is afforded in a virtual world. As well, while achieving realism has been a main goal in making convincing VR environments, just what constitutes realism and how much is needed is still an open question situated firmly in the research domain. Just as in real “reality,” such factors in virtual reality are complex and multivariate, and the understanding of this complexity presents exceptional challenges to the VR researcher. For certain research questions, good behavioral science often requires consistent delivery of stimuli within tightly controlled lab-based experimental conditions. However, for other important research questions we do not want to constrain naturalistic behavior and limit VR’s ability to replicate real world conditions, simply because it is easier to study human performance with traditional lab-based methodologies. By doing so we may compromise the very qualities that comprise VR’s unique capacity to mimic the experiences and challenges that exist in everyday life. What is really needed to address scientific questions that require natural exploration of a simulated environment are more usable and robust tools to instrument, organize, and visualize the complex data generated by measurements of participant behaviors within a virtual world. This paper briefly describes the rationale and methodology of an initial study in an ongoing research program that aims to investigate human performance within a virtual environment where unconstrained “free will” exploratory behavior is essential to research questions that involve the relationships between physiology, emotion, and memory. After a discussion of the research protocol and the types of data that were collected, we describe a novel tool that was borne from our need to more efficiently capture, manage, and explore the complex data that was generated in this research. An example of a research participant’s annotated display from this data management and visualization tool is then presented. It is our view that this tool provides the capacity to better visualize and understand the complex data relationships that may arise in VR research that investigates naturalistic free will behavior and its impact on other human performance variables.  相似文献   

20.
For the design and declaration of conservation areas as well as for planning habitat management it is important to quantitatively know the habitat preferences of the focal species. To take into account the requirements of as many species as possible, it would be of great advantage if one would either (i) find one or several species whose habitat requirements cover those of a large number of other species or if one could (ii) identify a common set of habitat parameters that is important for the occurrence of many species. Ideally such common habitat parameters should be easy to measure. Only then they may be of practical value in applied conservation biology.In this study, we compared the habitat preferences of different insect species (grasshoppers, bush crickets, butterflies, moths) in the same region by applying identical methods. To identify common explanatory variables that predict the occurrence probability of these species, we first tested the transferability of the specific ‘species models’ to other species within the same insect group. We tested how well the incidence of one species can be predicted by the occurrence probability of another species. The ‘best’ models within each group were then tested for transferability between the different groups. Additionally, we tested the predictive power of the predictor variable ‘habitat type’ as an easy and often available measure for conservation practice.Although in the different ‘species models’ different key factors determine habitat suitability, some models were successfully transferred and were able to reasonably predict the distribution of other species. The habitat preferences of the burnet moth Zygaena carniolica were particularly well suited for the prediction of suitable habitats for all other species. In addition, the predictor variable ‘habitat type’ played a dominant role in all models. Models using this aggregated predictor variable may well predict suitable habitat for all species.  相似文献   

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