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Results 501 - 550 of 1036
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Weber Kristi - - 2006
Americans are spending an increasing amount of time using "new media" like the Internet. There has been little research examining food and beverage Web sites' content and marketing practices, especially those that attract children and adolescents. The purpose of this study was to conduct a content analysis of food- and ...
Wilf Peter - - 2006
Food web recovery from mass extinction is poorly understood. We analyzed insect-feeding damage on 14,999 angiosperm leaves from 14 latest Cretaceous, Paleocene, and early Eocene sites in the western interior United States. Most Paleocene floras have low richness of plants and of insect damage. However, a low-diversity 64.4-million-year-old flora from ...
Maxwell T A D - - 2006
Abundance-body size relationships are widely observed macroecological patterns in complete food webs and in taxonomically or functionally defined subsets of those webs. Observed abundance-body size relationships have frequently been compared with predictions based on the energetic equivalence hypothesis and, more recently, with predictions based on energy availability to different body ...
Rutz Christian - - 2006
Investigating food-limitation in generalist predators is difficult, because they can switch to alternative prey, when one of their staple prey becomes scarce. Apart from data on the dynamics of the predator population, a robust study requires: (i) a documentation of the predator's entire prey base; and (ii) an experimental or ...
Estrada Ernesto - - 2007
We analyse the robustness of food webs against species loss by considering the influence of several structural factors of the networks, such as connectance, degree distribution and expansibility. The last concept refers to the absence of structural bottlenecks in the food web, whose removal separate the network into large isolate ...
Mullowney Paul - - 2007
Techniques from queueing theory can be used to model the growth of individuals in a stochastic environment where the growth rate cannot exceed some physiological maximum. In the simplifying case where there are no metabolic costs and the individual has an unlimited gut size, a general theory for the probability ...
Roy Shovonlal - - 2007
Enrichment in resource availability theoretically destabilizes predator-prey dynamics (the paradox of enrichment). However, a minor change in the resource stoichiometry may make a prey toxic for the predator, and the presence of toxic prey affects the dynamics significantly. Here, theoretically we explore how, at increased carrying capacity, a toxic prey ...
Jezbera Jan - - 2006
An experiment designed to examine food preferences of heterotrophic nanoflagellates (HNF) grazing on bacterioplankton was performed in the freshwater Rímov reservoir (Czech Republic). Water samples were size-fractionated to obtain < 5 microm filtrate containing bacteria and HNF. To manipulate resource availability, < 5 microm treatments were incubated in dialysis bags ...
Gandhi Nilima - - 2006
A multichemical food web model has been developed to estimate the biomagnification of interconverting chemicals in aquatic food webs. We extended a fugacity-based food web model for single chemicals to account for reversible and irreversible biotransformation among a parent chemical and transformation products, by simultaneously solving mass balance equations of ...
Rooney Neil - - 2006
Untangling the influence of human activities on food-web stability and persistence is complex given the large numbers of species and overwhelming number of interactions within ecosystems. Although biodiversity has been associated with stability, the actual structures and processes that confer stability to diverse food webs remain largely unknown. Here we ...
Lafferty Kevin D - - 2006
Parasitism is the most common animal lifestyle, yet food webs rarely include parasites. The few earlier studies have indicated that including parasites leads to obvious increases in species richness, number of links, and food chain length. A less obvious result was that adding parasites slightly reduced connectance, a key metric ...
Arii Ken - - 2007
One of the key measures that have been used to describe the topological properties of complex networks is the "degree distribution", which is a measure that describes the frequency distribution of number of links per node. Food webs are complex ecological networks that describe the trophic relationships among species in ...
Eby Lisa A - - 2006
The establishment of exotic game fishes to enhance recreational fisheries through authorized and unauthorized stocking into freshwater systems is a global phenomenon. Stocked fishes are often top predators that either replace native top predators or increase the species richness of top predators. Many direct effects of stocking have been documented, ...
Purnell Mark A - - 2006
1. The threespine stickleback Gasterosteus aculeatus is an important model organism in studies of genomic and phenotypic evolution, adaptation and speciation. Fossil Gasterosteus offer the potential to test models derived from studies of extant fishes over true evolutionary time-scales. Competition for food resources, for example, plays an important part in ...
Pelletier E - - 2006
Organisms living in coastal waters are exposed to anthropogenic contaminants from terrestrial drainage, ice melting and maritime traffic and to enhanced UVB radiation (UVBR; 280-320 nm) caused by decreased concentrations of ozone in the stratosphere. This article reviews available information about the combined effects of UVBR and selected hydrosoluble contaminants ...
Long Zachary T - - 2006
1. Allometric theory makes specific predictions about how density, and consequently biomass, scale with organism size within trophic levels, across trophic levels and across food webs. 2. Diversity-yield relationships suggest that more diverse food webs can sometimes support more biomass through mechanisms involving niche complementarity or selection effects that are ...
Belzile Claude - - 2006
UV irradiance has a broad range of effects on marine planktonic organisms. Direct and indirect effects on individual organisms have complex impacts on food-web structure and dynamics, with implications for carbon and nutrient cycling. Mesocosm experiments are well suited for the study of such complex interrelationships. Mesocosms offer the possibility ...
Filippini Manuela - - 2006
The discovery of an abundant and diverse virus community in oceans and lakes has profoundly reshaped ideas about global carbon and nutrient fluxes, food web dynamics, and maintenance of microbial biodiversity. These roles are exerted through massive viral impact on the population dynamics of heterotrophic bacterioplankton and primary producers. We ...
Sábato Marco Aurélio Lima - - 2006
It is well established in the scientific literature that animal prey species reduce their activity at times of high predation risk. In the case of nocturnal animals this occurs when there is a full moon; however, the response of predators to the changes in their prey behaviour is relatively unknown. ...
van de Wolfshaar K E - - 2006
Growth in body size during ontogeny often results in changes in diet, leading to life-history omnivory. In addition, growth is often dependent on food density. Using a physiologically structured population model, we investigated the effects of these two aspects of individual growth in a system consisting of two size-structured populations, ...
Cross W F - - 2006
Although the effects of nutrient enrichment on consumer-resource dynamics are relatively well studied in ecosystems based on living plants, little is known about the manner in which enrichment influences the dynamics and productivity of consumers and resources in detritus-based ecosystems. Because nutrients can stimulate loss of carbon at the base ...
Wise David H - - 2006
The effectiveness of generalist predators in biological control may be diminished if increased availability of alternative prey causes individual predators to decrease their consumption of crop pests. Farming practices that enhance densities of microbidetritivores in the detrital food web can lead to increased densities of generalist predators that feed on ...
Smee Delbert L - - 2006
The lethal and nonlethal impacts of predators in marine systems are often mediated via reciprocal detection of waterborne chemical signals between consumers and prey. Local flow environments can enhance or impair the chemoreception ability of consumers, but the effect of hydrodynamics on detection of predation risk by prey has not ...
Halpern Benjamin S - - 2006
Global-scale changes in anthropogenic nutrient input into marine ecosystems via terrestrial runoff, coupled with widespread predator removal via fishing, have created greater urgency for understanding the relative role of top-down versus bottom-up control of food web dynamics. Yet recent large-scale studies of community regulation in marine ecosystems have shown dramatically ...
Sims David W - - 2006
Movements of wide-ranging top predators can now be studied effectively using satellite and archival telemetry. However, the motivations underlying movements remain difficult to determine because trajectories are seldom related to key biological gradients, such as changing prey distributions. Here, we use a dynamic prey landscape of zooplankton biomass in the ...
Hudson Peter J - - 2006
Historically, the role of parasites in ecosystem functioning has been considered trivial because a cursory examination reveals that their relative biomass is low compared with that of other trophic groups. However there is increasing evidence that parasite-mediated effects could be significant: they shape host population dynamics, alter interspecific competition, influence ...
Hu Jianying - - 2006
Organotins, especially tributyltin (TBT) and triphenyltin (TPT), are of particular concern due to their ubiquity in the aquatic environment and theirtoxicityto aquatic organisms. This study reports field studies on trophic magnification factors (TMF) of TBT and TPT in a marine food web. TBT, TPT, and their metabolites in plankton, five ...
Ortega Yvette Katina - - 2006
Although exotic plant invasions threaten natural systems worldwide, we know little about the specific ecological impacts of invaders, including the magnitude of effects and underlying mechanisms. Exotic plants are likely to impact higher trophic levels when they overrun native plant communities, affecting habitat quality for breeding songbirds by altering food ...
Cole Jonathan J - - 2006
Organic carbon inputs from outside of ecosystem boundaries potentially subsidize recipient food webs. Four whole-lake additions of dissolved inorganic 13C were made to reveal the pathways of subsidies to lakes from terrestrial dissolved organic carbon (t-DOC), terrestrial particulate organic carbon (t-POC) and terrestrial prey items. Terrestrial DOC, the largest input, ...
Stumm, Karen
This thesis aimed at achieving a deeper understanding of the dynamics and structure of microbenthic communities with a focus on protists. The most important discovery concerning protozoa in recent years is the fact that they play a much more important role in for example carbon and energy flow in nature ...
Cadotte Marc W - - 2006
Community structure is the observable outcome of numerous processes. We conducted a laboratory experiment using a microbial model system to disentangle effects of nutrient enrichment, dispersal, and predation on prey species richness and predator abundance at local and metacommunity scales. Prey species included: Chilomonas sp., Colpidium striatum, Colpoda cucullus, Paramecium ...
Ghose Kaushik - - 2006
Acquisition of food in many animal species depends on the pursuit and capture of moving prey. Among modern humans, the pursuit and interception of moving targets plays a central role in a variety of sports, such as tennis, football, Frisbee, and baseball. Studies of target pursuit in animals, ranging from ...
Nfon Erick - - 2006
Multi-year monitoring data for PCBs in abiotic media and biota collected from the Baltic region were compiled into a database and analyzed using the equilibrium lipid partitioning (ELP) approach to study temporal trends as well as to investigate food web biomagnification. Statistically significant reductions in ELP concentrations between 1987 and ...
May Robert M - - 2006
A scientific growth area in recent years has been the study of networks of interacting entities within a population, including species in food webs, human or other animals transmitting infection, proteins in cells, cells in organisms (e.g. neuronal networks), the internet and the World Wide Web. Here, I review some ...
Barbosa L A - - 2006
In the last three decades, researchers have tried to identify universal patterns in the structure of food webs. It was recently proposed that the exponent eta characterizing the efficiency of the transport of energy in large and small food webs might have a universal value (eta = 1.13). In this ...
Xinyao Liu - - 2006
Bacterivory by heterotrophic nanoflagellates and ciliates has been widely studied in aquatic environments, but data on the grazing of amoebae, are still scarce. From the water samples of Dianchi Lake (Kunming, Yunnan Province, China), we isolated an amoeba, designated as Naegleria sp. strain W2, which had potent grazing effects on ...
Gratton Claudio - - 2006
Restoration of habitats impacted by invasive plants is becoming an increasingly important tool in the management of native biodiversity, though most studies do not go beyond monitoring the abundance of particular taxonomic groups, such as the return of native vegetation. Yet, the reestablishment of trophic interactions among organisms in restored ...
Darst Catherine R - - 2006
Many animals advertise their chemical defense to predators with conspicuous coloration and unpalatability, but little is known about the information in these signal elements. To effectively avoid predation, is it more advantageous to invest in increased conspicuousness or greater noxiousness, or to allocate equally to both signal modalities? Using natural ...
Katechakis Alexis - - 2006
Mixotrophic organisms combine light, mineral nutrients, and prey as supplementary resources. Based on theoretical assumptions and field observations, we tested experimentally the hypothesis that mixotrophs may invade established plankton communities depending on the trophic status of the system, and investigated possible effects on food web structure, species diversity, and nutrient ...
Lin Hsing-Juh - - 2006
Tapong Bay, a eutrophic and poorly flushed tropical lagoon, supports intensive oyster culture. Using the Ecopath approach and network analysis, a mass-balanced trophic model was constructed to analyze the structure and matter flows within the food web. The lagoon model is comprised of 18 compartments with the highest trophic level ...
Tewksbury Joshua J - - 2006
The effects of landscape fragmentation on nest predation and brood parasitism, the two primary causes of avian reproductive failure, have been difficult to generalize across landscapes, yet few studies have clearly considered the context and spatial scale of fragmentation. Working in two river systems fragmented by agricultural and rural-housing development, ...
Virgo Nathaniel - - 2006
1. Successional changes during sequential assembly of food webs were examined. This was carried out by numerical methods, drawing one species at a time from a species pool and obtaining the permanent (persistent) community emerging at each step. Interactions among species were based on some simple rules about body sizes ...
Meissner Kristian - - 2006
1. We evaluated the effects of brown trout on boreal stream food webs using field surveys and enclosure/exclosure experiments. Experimental results were related to prey preference of uncaged trout in the same stream, as well as to a survey of macroinvertebrate densities in streams with vs. without trout. Finally, we ...
Elser James J - - 2006
Here we use the theory of ecological stoichiometry to propose and provide a preliminary test of a novel hypothesis that the Cambrian 'explosion' may have been triggered by changes in circulating P availability in the biosphere. We exposed living stromatolites from a spring-fed stream in Mexico to a gradient of ...
Haugstvedt Jan-Ragnar - - 2006
PURPOSE: Laboratory studies evaluating the importance of the stabilizing structures of the distal radioulnar joint (DRUJ) largely have been limited to static design. Clinically, dynamic loading seems to be an important component of DRUJ instability. This study was designed to evaluate the influence of dynamic loading on the stability of ...
Niessen L - - 2006
Ochratoxin A (OTA) can be detected worldwide from various food and feed sources. It is produced byPenicillium nordicum andP. verrucosum as well as by variousAspergillus species, withA. ochraceus andA. carbonarius as the predominant producers. Various pairs of PCR primers based on AFLP, RAPD as well as primers specific to ribosomal ...
Essington Timothy E - - 2006
A recurring pattern of declining mean trophic level of fisheries landings, termed "fishing down the food web," is thought to be indicative of the serial replacement of high-trophic-level fisheries with less valuable, low-trophic-level fisheries as the former become depleted to economic extinction. An alternative to this view, that declining mean ...
Gilman Sarah E - - 2006
Experimental studies of biogeographic processes are important, but rarely attempted because of the logistical challenges of research at large spatial scales. I used a series of large-scale transplant experiments to investigate the mechanisms controlling species abundance near a poleward range boundary. The intertidal limpet Collisella scabra experiences a 100-fold decline ...
Rossberg A G - - 2006
Food webs of habitats as diverse as lakes or desert valleys are known to exhibit common "food-web patterns", but the detailed mechanisms generating these structures have remained unclear. By employing a stochastic, dynamical model, we show that many aspects of the structure of predatory food webs can be understood as ...
Bergman Eric J - - 2006
Within predator-prey systems behavior can heavily influence spatial dynamics, and accordingly, the theoretical study of how spatial dynamics relate to stability within these systems has a rich history. However, our understanding of these behaviors in large mammalian systems is poorly developed. To address the relationship between predator selection patterns, prey ...
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