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Efforts to restore top predators in human-altered systems raise the question of whether rebounds in predator populations are sufficient to restore pristine foodweb dynamics. Ocean ecosystems provide an ideal system to test this question. Removal of fishing in marine reserves often reverses declines in predator densities and size. However, whether this leads to restoration of key functional characteristics of foodwebs, especially prey foraging behavior, is unclear. The question of whether restored and pristine foodwebs function similarly is nonetheless critically important for management and restoration efforts. We explored this question in light of one important determinant of ecosystem function and structure--herbivorous prey foraging behavior. We compared these responses for two functionally distinct herbivorous prey fishes (the damselfish Plectroglyphidodon dickii and the parrotfish Chlorurus sordidus) within pairs of coral reefs in pristine and restored ecosystems in two regions of these species' biogeographic ranges, allowing us to quantify the magnitude and temporal scale of this key ecosystem variable's recovery. We demonstrate that restoration of top predator abundances also restored prey foraging excursion behaviors to a condition closely resembling those of a pristine ecosystem. Increased understanding of behavioral aspects of ecosystem change will greatly improve our ability to predict the cascading consequences of conservation tools aimed at ecological restoration, such as marine reserves.  相似文献   

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Mott KA 《Plant physiology》1988,86(1):200-203
Most studies on stomatal responses to CO2 assume that guard cells respond only to intercellular CO2 concentration and are insensitive to the CO2 concentrations in the pore and outside the leaf. If stomata are sensitive to the CO2 concentration at the surface of the leaf or in the stomatal pore, the stomatal response to intercellular CO2 concentration will be incorrect for a `normally' operating leaf (where ambient CO2 concentration is a constant). In this study asymmetric CO2 concentrations for the two surfaces of amphistomatous leaves were used to vary intercellular and leaf surface CO2 concentrations independently in Xanthium strumarium L. and Helianthus annuus L. The response of stomata to intercellular CO2 concentration when the concentration at the leaf surface was held constant was found to be the same as the response when the surface concentration was varied. In addition, stomata did not respond to changes in leaf surface CO2 concentration when the intercellular concentration for that surface was held constant. It is concluded that stomata respond to intercellular CO2 concentration and are insensitive to the CO2 concentration at the surface of the leaf and in the stomatal pore.  相似文献   

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A cell's decision to divide must be regulated with the highest fidelity. Otherwise, abnormalities occurring in the replication of genetic material and cytokinesis would be incompatible with life. It has been known for almost a century that cells comprising a population undergo cellular division at extremely variable rates, even though genetically identical cell clones have been examined. Studies with T lymphocytes at the single cell level have revealed that the rate of cellular division is determined by the accumulation of a critical number of ligand-triggered interleukin-2 (IL2) receptors at the cell surface throughout the G1 phase of the cell cycle. Thus, the cell “counts” the number of triggered IL2 receptors, and only decides to divide when the critical number has been attained. This information is then transferred to the cellular interior via intracellular sensors comprised of D-type cyclins, which ultimately determine when the cell surpasses the “Restriction Point” in late G1, and which commits the cell irrevocably to initiate DNA replication. Beyond the R-point, the cell assembles a definite number of macromolecular pre-replication complexes (Pre-RCs) comprised of at least 6 distinct proteins at sites of the origin of replication on DNA. Complete assembly of the Pre-RCs is a prerequisite for their subsequent disassembly, which must occur before the initiation of DNA strand replication, and which occurs asynchronously throughout the S-phase of the cell cycle and only terminates when the entire DNA has been duplicated. Thus, the fidelity of the decision to divide is exquisitely regulated by macromolecular mechanisms initiated at the cell surface and transferred to the cellular interior so that the cell can make the decision in a quantal (all-or-none) fashion. The question before us is how this quantal decision is made at the molecular level. The available data indicate that the assembly and disassembly of a definite number of large multicomponent macromolecular complexes make the quantal decisions. Here, it is postulated that all fundamental cellular decisions, i.e. survival, death, proliferation and differentiation, are regulated in this fashion. It remains to be determined how the cell counts the signals it receives, and what the molecular forces are that dictate the behavior of macromolecular complexes. Alexander Hamilton: “The best security for the fidelity of men, is to make interest coincide with duty.”  相似文献   

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Symons N  Svensson PA  Wong BB 《PloS one》2011,6(6):e20576
Males often play a critical role in offspring care but the time and energy invested in looking after young can potentially limit their ability to seek out additional mating opportunities. Recent studies, however, suggest that a conflict between male parental effort and mating effort may not always be inevitable, especially if breeding occurs near the nest, or if parental behaviours are under sexual selection. Accordingly, we set out to experimentally investigate male care and courtship in the desert goby Chlamydogobius eremius, a nest-guarding fish with exclusive paternal care. Despite courtship occurring near the nest, we found that when egg-tending males were given the opportunity to attract additional females, they fanned their eggs less often, engaged in shorter fanning bouts, and spent more of their time outside their nests courting. Our findings highlight the importance of understanding the circumstances under which reproductive tradeoffs are expected to occur and how these, in turn, operate to influence male reproductive decisions.  相似文献   

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Mangrove Restoration: Do We Know Enough?   总被引:11,自引:0,他引:11  
Mangrove restoration projects have been attempted, with mixed results, throughout the world. In this paper, I first examine goals of existing mangrove restoration projects and determine whether these goals are clear and adequate, and whether or not they account for the full range of biological diversity and ecological processes of mangrove ecosystems. Many restored mangrove forests resemble forest plantations rather than truly integrated ecosystems, but mangrove plantations can be a first step toward mangrove rehabilitation. Mangrove restoration projects that involve associated aquaculture or mariculture operations tend to be more likely to approximate the biological diversity and ecological processes of undisturbed mangrove ecosystems than are projects that focus only on the trees. These integrated restoration projects also provide a higher economic return than do silvicultural projects alone. Second, I briefly assess whether existing ecological data are sufficient to undergird successful restoration of mangal and define criteria for determining whether or not a mangrove ecosystem has been restored successfully. These criteria include characteristics of vegetation (forest) structure, levels of primary production, composition of associated animal communities, and hydrology. Finally, I suggest ways to improve mangrove restoration projects and identify key research needs required to support these efforts. Ecological theories derived from other wetland and upland systems rarely have been applied to either “basic” or “applied” mangrove forest studies, to the detriment of restoration projects, whereas lessons from restoration of the relatively species‐poor mangrove ecosystems could be beneficially applied to restoration projects in other contexts. An international database of mangrove restoration projects would reduce the likelihood that unsuccessful restoration projects would be repeated elsewhere. Clear criteria for evaluating success, greater accessibility of information by managers in the developing world, intensified international cooperation, and application of relevant ecological theories will improve the success rate of mangrove restoration projects.  相似文献   

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The Yale Cognitive Science department hosted the conference “From Habits to Self-Regulation: How Do We Change?” on November 4 and 5, 2011, to showcase current research on self-control in cognitive science, psychology, and neuroscience. The conference included a panel discussion by four philosophers who gave context for the scope and limitations of research on self-control. The common theme concerning the best method to attain lasting change included becoming aware of what one wants to change, increasing commitment to the goal of change, and imagining all of the potential problems and solutions to those problems.  相似文献   

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This is a review on benthic algae from streams situated above the tree line in the Alps. It integrates published and unpublished data from alpine streams in Austria and in the Trento Province (Northern Italy). The main focus is on the structural and taxonomic composition of benthic algae including macro- and micro-algae and their contribution to the epilithic biofilm and the stream food-web. The environmental conditions relevant to algae within the two major stream types, the glacial (glacier-fed) and non-glacial krenal (spring-fed) stream are discussed. The paper considers both the maximum possible structural complexity of transverse algae zonation in cascading alpine/subalpine stream segments, and the effects of glacial water on species richness in the Central Alps in Austria. Autecological data are given for 46 common diatoms from 42 sites in the Central Eastern and Southern Central Alps and for 30 algae in addition to diatoms for 22 streams in the Central Eastern Alps. Since data on responses of benthic algae to the harsh conditions in high altitude Alpine streams are very scarce, results from literature and the author’s experiences from these and other mountain stream types are synthesized to formulate major objectives for future research in benthic high altitude Alpine stream ecology.  相似文献   

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Objectives

How medical students handle negative emotions expressed by simulated patients during Objective Structured Clinical Examinations (OSCE) has not been fully investigated. We aim to explore (i) whether medical students respond differently to different types of patients’ emotional cues; and (2) possible effects of patients’ progressive disclosure of emotional cues on students’ responses.

Methods

Forty OSCE consultations were video recorded and coded for patients’ expressions of emotional distress and students’ responses using a validated behavioural coding scheme (the Verona Coding Definitions of Emotional Sequence). Logistic multilevel regression was adopted to model the probability of the occurrence of student reduce space response behaviour as a function of the number of patients’ expressions of emotional cues.

Results

We found that medical students offered responses that differed to emotional cue types expressed by simulated patients. Students appeared to provide space to emotional cues when expressed in vague and unspecific words and reduce space to cues emphasizing physiological or cognitive correlates. We also found that medical students were less likely to explore patients’ emotional distress nearer the end of the consultation and when the duration of a patient speech turn got larger. Cumulative frequency of patients’ emotional cues also predicted students’ reduce space behaviour.

Practical Implications

Understanding how medical students manage negative emotions has significant implications for training programme development focusing on emotion recognition skills and patient-centred communication approach. In addition, the statistical approaches adopted by this study will encourage researchers in healthcare communication to search for appropriate analytical techniques to test theoretical propositions.  相似文献   

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How Much Ecology Do We Need to Know to Restore Mediterranean Ecosystems?   总被引:2,自引:1,他引:1  
Despite important advances in ecological knowledge of Mediterranean‐type ecosystems, advances in restoration ecology have not seen a parallel increase in these systems. Although some concepts such as positive plant–plant interaction (facilitation) have received attention in the restoration ecology community, others such as phenotypic plasticity have not. Some concepts (e.g., environmental heterogeneity) are mature enough for a wide use in restoration, whereas available knowledge on others (e.g., facilitation, plasticity) is less conclusive. However, the scientific knowledge is in general enough to significantly improve the guidelines for restoration of Mediterranean ecosystems. Our review suggests that (1) the extent of facilitation in dry ecosystems is partially understood, with supporting, but somewhat contradictory empirical evidence for its potential use in restoration; (2) the influence of habitat heterogeneity on plant performance and plasticity is only beginning to be understood, with a strong bias toward patterns of structural heterogeneity and negligible information on functional heterogeneity; and (3) sound evaluations of phenotypic plasticity might be useful to increase the success of restoration practices in patchy Mediterranean environments. Future global change scenarios involving temperature rise, reduced precipitation, increased frequency of extreme climatic events, and important land use changes and fragmentation must be particularly considered when restoring Mediterranean ecosystems. Further research on how to incorporate results on facilitation, environmental heterogeneity, and plasticity within a global change framework is clearly needed.  相似文献   

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Background

Can political controversy have a “chilling effect” on the production of new science? This is a timely concern, given how often American politicians are accused of undermining science for political purposes. Yet little is known about how scientists react to these kinds of controversies.

Methods and Findings

Drawing on interview (n = 30) and survey data (n = 82), this study examines the reactions of scientists whose National Institutes of Health (NIH)-funded grants were implicated in a highly publicized political controversy. Critics charged that these grants were “a waste of taxpayer money.” The NIH defended each grant and no funding was rescinded. Nevertheless, this study finds that many of the scientists whose grants were criticized now engage in self-censorship. About half of the sample said that they now remove potentially controversial words from their grant and a quarter reported eliminating entire topics from their research agendas. Four researchers reportedly chose to move into more secure positions entirely, either outside academia or in jobs that guaranteed salaries. About 10% of the group reported that this controversy strengthened their commitment to complete their research and disseminate it widely.

Conclusions

These findings provide evidence that political controversies can shape what scientists choose to study. Debates about the politics of science usually focus on the direct suppression, distortion, and manipulation of scientific results. This study suggests that scholars must also examine how scientists may self-censor in response to political events.  相似文献   

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Evidence shows that the font size of study items significantly influences judgments of learning (JOLs) and that people’s JOLs are generally higher for larger words than for smaller words. Previous studies have suggested that font size influences JOLs in a belief-based way. However, few studies have directly examined how much people’s beliefs contribute to the font-size effect in JOLs. This study investigated the degree to which font size influenced JOLs in a belief-based way. In Experiment 1, one group of participants (learners) studied words with different font sizes and made JOLs, whereas another group of participants (observers) viewed the learners'' study phase and made JOLs for the learners. In Experiment 2, participants made both JOLs and belief-based recall predictions for large and small words. Our results suggest that metamemory beliefs play an important role in the font-size effect in JOLs.  相似文献   

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In some plant species the whole shoot is occasionally removed, as a result of specialist herbivory, grazing, mowing, or other causes. The plant can adapt to defoliation by allocating more to tolerance and less to growth and defense. Plant tolerance to defoliation (TOL1) is typically measured as the ratio between the average dry weight of a group of damaged plants and a control group of undamaged plants, both measured some time after recovery. We develop a model to clarify what TOL1 actually measures. We advocate keeping regrowth (REG2) and shoot–root ratio, both elements of TOL1, separate in the analysis. Based on a resource trade‐off, exotic Jacobaea vulgaris plants from populations in the USA (no specialist herbivory) are expected to grow faster and be less tolerant than native Dutch populations (with specialist herbivory). Indeed Dutch plants had both a significantly larger fraction biomass in roots and faster regrowth (REG2), while US plants attained the highest weight in the control without defoliation. Using key‐factor analysis, we illustrate how growth rates, regrowth, and shoot–root ratio each contribute to final biomass (plant fitness). Our proposed method gives more insight in the mechanisms that underly plant tolerance against defoliation and how tolerance contributes to fitness.  相似文献   

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Sequential enzymes in biosynthetic pathways are organized in metabolons. It is challenging to provide experimental evidence for the existence of metabolons as biosynthetic pathways are composed of highly dynamic protein–protein interactions. Many different methods are being applied, each with strengths and weaknesses. We will present and evaluate several techniques that have been applied in providing evidence for the orchestration of the biosynthetic pathways of cyanogenic glucosides and glucosinolates in metabolons. These evolutionarily related pathways have ER-localized cytochromes P450 that are proposed to function as anchoring site for assembly of the enzymes into metabolons. Additionally, we have included commonly used techniques, even though they have not been used (yet) on these two pathways. In the review, special attention will be given to less-exploited fluorescence-based methods such as FCS and FLIM. Ultimately, understanding the orchestration of biosynthetic pathways may contribute to successful engineering in heterologous hosts.  相似文献   

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