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991.
Sherratt TN 《Die Naturwissenschaften》2008,95(8):681-695
It is now 130 years since Fritz Müller proposed an evolutionary explanation for the close similarity of co-existing unpalatable prey species, a phenomenon now known as Müllerian mimicry. Müller's hypothesis was that unpalatable species evolve a similar appearance to reduce the mortality involved in training predators to avoid them, and he backed up his arguments with a mathematical model in which predators attack a fixed number (n) of each distinct unpalatable type in a given season before avoiding them. Here, I review what has since been discovered about Müllerian mimicry and consider in particular its relationship to other forms of mimicry. Müller's specific model of associative learning involving a "fixed n" in a given season has not been supported, and several experiments now suggest that two distinct unpalatable prey types may be just as easy to learn to avoid as one. Nevertheless, Müller's general insight that novel unpalatable forms have higher mortality than common unpalatable forms as a result of predation has been well supported by field experiments. From its inception, there has been a heated debate over the nature of the relationship between Müllerian co-mimics that differ in their level of defence. There is now a growing awareness that this relationship can be mediated by many factors, including synergistic effects between co-mimics that differ in their mode of defence, rates of generalisation among warning signals and concomitant changes in prey density as mimicry evolves. I highlight areas for future enquiry, including the possibility of Müllerian mimicry systems based on profitability rather than unprofitability and the co-evolution of defence. 相似文献
992.
Mr. M. T. Rebello G. Hackett J. Smith F. E. Loeffler S. Robson N. Maclachlan R. W. Beard C. H. Rodeck R. Williamson D. V. Coleman C. Williams 《黑龙江环境通报》1991,11(1):41-46
Ten-ml samples of amniotic fluid were taken from pregnancies being terminated at 8–14 weeks' gestation. DNA was extracted from the amniotic cells by sequential centrifugation and analysed using the polymerase chain reaction (PCR). Fifteen samples were analysed for evidence of maternal contamination using Mfd5 oligo-nucleotide primers for repeat polymorphisms. Ten amniotic fluid samples were tested for the Delta-F508 deletion characteristic of cystic fibrosis to demonstrate a diagnostic application for the technique. In each case, DNA extracted from fetal tissue from the same pregnancy was included in the controls. In 14 of the 15 cases tested with the Mfd5 primers, both the amniotic fluid DNA and the fetal DNA showed no evidence of contaminating DNA. In one case, neither the amniotic fluid cells nor the fetal cells yielded results. In nine of the ten cases tested with the Delta-F508 primers, the amniotic fluid cell DNA provided accurate information about the genetic status of the fetus; in the tenth, the fetal DNA failed to amplify. The results indicate that adequate DNA can be extracted from amniotic fluid from 8 weeks' gestation onward and these samples are suitable for prenatal diagnosis using PCR. 相似文献
993.
Zoning and applying Limits of Acceptable Change (LAC) are two promising strategies for managing tourism in Marine Protected
Areas (MPAs). Typically, these management strategies require the collection and integration of ecological and socioeconomic
data. This problem is illustrated by a case study of Koh Chang National Marine Park, Thailand. Biophysical surveys assessed
coral communities in the MPA to derive indices of reef diversity and vulnerability. Social surveys assessed visitor perceptions
and satisfaction with conditions encountered on snorkelling tours. Notably, increased coral mortality caused a significant
decrease in visitor satisfaction. The two studies were integrated to prescribe zoning and “Limits of Acceptable Change” (LAC).
As a biophysical indicator, the data suggest a LAC value of 0.35 for the coral mortality index. As a social indicator, the
data suggest that a significant fraction of visitors would find a LAC value of under 30 snorkellers per site as acceptable.
The draft zoning plan prescribed four different types of zones: (I) a Conservation Zone with no access apart from monitoring
or research; (II) Tourism Zones with high tourism intensities at less vulnerable reefs; (III) Ecotourism zones with a social
LAC standard of <30 snorkellers per site, and (IV) General Use Zones to meet local artisanal fishery needs. This study illustrates
how ecological and socioeconomic field studies in MPAs can be integrated to craft zoning plans addressing multiple objectives. 相似文献
994.
Richard C. Foltz 《Journal of Agricultural and Environmental Ethics》2007,20(6):533-542
995.
Başak K. Taşeli 《The Environmentalist》2007,27(3):315-327
Environmental pollution and degradation of ecosystems considerably affect the natural resources. The Turkish Government is
aware of the importance of the preservation of natural ecology and thereby the environmental conservation of many species
in their natural habitat. This paper provides critical assessments of the problems and possible solutions in the identification,
implementation and management of the Specially Protected Areas (SPAs) system by giving basic information about stakeholders
and their responsibilities that currently offer nature conservation in Turkey. The goals of the article are to analyze how
the SPAs interface with the local people, especially the villagers who have dwelt there before SPA designation and how people-SPA
conflicts resolved; to show how effective the SPA conservation objectives have been; to outline the significance of informing
and empowering people in nature conservation for the protected area management and to show the importance of planning at all
levels during protection of the natural, archeological and cultural values of the SPAs. 相似文献
996.
In the United States, the Clean Water Act requires mitigation for wetlands that are negatively impacted by dredging and filling
activities. During the mitigation process, there generally is little effort to assess function for mitigation sites and function
is usually inferred based on vegetative cover and acreage. In our study, hydrogeomorphic (HGM) functional assessment models
were used to compare predicted and potential levels of functional capacity in created and natural reference wetlands. HGM
models assess potential function by measurement of a suite of structural variables and these modeled functions can then be
compared to those in natural, reference wetlands. The created wetlands were built in a floodplain setting of a valley in central
Pennsylvania to replace natural ridge-side slope wetlands. Functional assessment models indicated that the created sites differed
significantly from natural wetlands that represented the impacted sites for seven of the ten functions assessed. This was
expected because the created wetlands were located in a different geomorphic setting than the impacted sites, which would
affect the type and degree of functions that occur. However, functional differences were still observed when the created sites
were compared with a second set of reference wetlands that were located in a similar geomorphic setting (floodplain). Most
of the differences observed in both comparisons were related to unnatural hydrologic regimes and to the characteristics of
the surrounding landscape. As a result, the created wetlands are not fulfilling the criteria for successful wetland mitigation. 相似文献
997.
Ben A. Minteer Elizabeth A. Corley 《Journal of Agricultural and Environmental Ethics》2007,20(4):307-333
Few disputes in the annals of US environmentalism enjoy the pedigree of the conservation-preservation debate. Yet, although
many scholars have written extensively on the meaning and history of conservation and preservation in American environmental
thought and practice, the resonance of these concepts outside the academic literature has not been sufficiently examined.
Given the significance of the ideals of conservation and preservation in the justification of environmental policy and management,
however, we believe that a more detailed analysis of the real-world use and understanding of these ideas is needed. In this
paper, we describe the results of a qualitative, semantic study of the concepts of conservation and preservation undertaken
in the context of the Chattahoochee National Forest (CNF), located in northern Georgia (USA). Thirty in-depth interviews were
conducted with scientists and north Georgia residents either interested or involved in the future management of the forest.
Respondents were asked to define conservation and preservation in their own words and to indicate which approach they felt
was more appropriate for the management of the CNF. Qualitative content analysis was used to elicit a set of recurring themes
for each foundational concept. Taken together, these themes help to flesh out the meaning of conservation and preservation
for citizens and scientists today, and illustrate the evolving nature of two of the more significant and venerable ideas animating
US environmental policy and management. 相似文献
998.
Marko S. Markov 《The Environmentalist》2007,27(4):465-475
Magnetic and electromagnetic fields are now recognized by the 21st century medicine as real physical entities that promise
the healing of various health problems, even when conventional medicine has failed. Today magnetotherapy provides a non-invasive,
safe, and easy method to directly treat the site of injury, the source of pain and inflammation, and other types of diseases
and pathologies. Millions of people worldwide have received help in treatment of musculoskeletal system, as well as pain relief.
Pulsed electromagnetic fields are one important modality in magnetotherapy and recent technological innovations, such as Curatron
pulsed electromagnetic field devices, offer excellent, state of the art computer controlled therapy system. In this article
the development, state of the art and future of pulsed electromagnetic field therapy are discussed. 相似文献
999.
The paper is devoted to the phenomenon of methanogenic activity of woody debris, i.e., methane production in the course of wood decomposition by fungi, which are not directly involved in methane synthesis but form an initial link in the trophic chain leading to methanogenic archaea. Expert evaluation of probable amounts of methane emission is made. The results show that woody debris is an important global source of this greenhouse gas. 相似文献
1000.