Xem 1-20 trên 37 kết quả Food webs
  • Looking up ‘‘aquatic food web’’ on Google provides a dizzying array of eclectic sites and information (and disinformation!) to choose from. However, even within this morass it is clear that aquatic food-web research has expanded greatly over the last couple of decades, and includes a wide array of studies from both theoretical and empirical perspectives. This book attempts to bring together and synthesize some of the most recent perspectives on aquatic food-web research, with a particular emphasis on integrating that knowledge within an ecosystem framework....

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  • Challenges to sustaining the productivity of oceanic and coastal fisheries have become more critical and complex as these fisheries reach the upper limits to ocean harvests. In addition, it is now clear that we are managing interactive and dynamic food webs rather than sets of independent single-species populations.

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  • Significantly revised and updated, this second edition of the bestselling Handbook of Nutrition and Food welcomes contributions from several new authors, including Elaine B. Feldman and Johanna Dwyer, notable leaders in nutritional science. Retaining the high level of scientific research, accessible language, and attention to detail of the original, this new edition reflects the changes and developments of the past six years in nutrition research by adding 12 new chapters and tripling the number of referential web addresses. ...

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  • This book proposes a framework for a national-scale program to monitor changes in mercury concentrations in the environment following the reduction of atmospheric mercury emissions. The book is the product of efforts initiated at a workshop held in Pensacola, Florida, in September 2003, involving more than 30 experts in the fields of atmospheric mercury transport and deposition, mercury cycling in terrestrial and aquatic ecosystems, and mercury bioaccumulation in aquatic food webs and wildlife.

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  • No matter what export markets and outlets you target, in this day and age you must be visible to consumers online. Having your own website is valuable whether you are selling your products directly from your own site or just linking your website to the sites where your products are available for purchase. (E.g. your distributor, retail shops or catalogs that carry your products.) If you do not have the capacity to sell products from your own website, concentrate on a few good web pages that tell your products’ stories using compelling pictures.

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  • To get interested consumers to your website, the site needs to be visible to surfers using Google. Why is Google so important? The research firm Hitwise which measures Web audiences, estimates that Google has 72% of the US search engine market, versus 17.9 % for Yahoo. Microsoft’s two search services, MSN and Live.com, constitute a distant third, at a combined 5.4 percent. Many website owners who track where their visitors come from report that Google’s search engine now refers 80 to 90% of their visitors. 2 For optimal results on Google you will want...

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  • The Cork Wholesale Food Company has just had a Frame Relay circuit installed to its local central office (CO) by the telco carrier. The network administrator must confirm that the router and Frame Relay switch are able to successfully communicate.

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  • Chapter 20 Food Webs In the previous chapter we began to consider how population interactions can shape communities. Our focus was on interactions between species occupying the same trophic level or between members of adjacent trophic levels.

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  • 27 Effects of Contaminants on Trophic Structure and Food Webs The empirical patterns are widespread and abundantly documented, but instead of an agreed explanation there is only a list of possibilities to be explored. (May 1981) There has been little synthesis of the relative roles of different ecological forces in determining population change and community structure. Rather, there is a collection of idiosyncratic systems, with their associated protagonists, in which opposing views on the importance of particular factors are debated. (Hunter and Price 1992) 27.

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  • This is a frightening development. There are traces within you – or, depending on your circumstances and exposures, more than traces – of several hundred man-made chemicals. Many are harmless (or at least are so far thought to be). Others, however, may cause cancer and damage the nervous systems, reproductive systems, immune systems, or livers of animals. Mounting scientific evidence is confirming long-term suspicions that they do the same to human beings.

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  • Benthic algae have been intensively studied, especially over the past two decades. This intensity has been stimulated by the widespread recognition that benthic algae are ideal indicators of the health of many, if not most, aquatic ecosystems. With this book we hope to synthesize this vital area of research and share its essence with our colleagues and students. We started with an outline of the myriad abiotic and biotic determinants of benthic algal ecology.

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  • Large lakes are important because of their size and ecological distinctiveness, as well as their economic and cultural value. Optimal management of them requires a proper understanding of anthropogenic impacts, both on the lake ecosystems, as such and on the services they provide for society. The specific structural and functional properties of large lakes, e.g. morphology, hydrography, biogeochemical cycles, and food-web structure, are all directly related to their size.

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  • Ants, single-celled creatures such as the cellular slime mold, plants and animals in ecosystems, and (even) human beings can congregate and display miraculously complex behaviors.* Say a colony of ants in a tree needs to move to another tree, perhaps in search of food. Some ants build a bridge by joining their bodies in a chain stretching from one limb in one tree to another limb in another tree. Other ants cross over this ant structure, walking over their peers. Once all the ants have crossed over, the ants in the bridge begin to gracefully undo the structure, crossing one by one.

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  • This book is about the distribution and abundance of different types of organism, and about the physical, chemical but especially the biological features and interactions that determine these distributions and abundances. Unlike some other sciences, the subject matter of ecology is apparent to everybody: most people have observed and pondered nature, and in this sense most people are ecologists of sorts. But ecology is not an easy science.

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  • The direction of science is often driven by methodological progress, and the topic of this book is no exception. I remember sitting with a visitor on the terrace of a hotel overlooking Lake Constance in the early 1970s. We were discussing the gravimetric method of measuring total lipids in zooplankton. A few years later, as a visitor in Clyde E. Goulden’s lab, I was greatly impressed by the ability of an instrument called an Iatroscan to discriminate and quantify specific lipid classes (e.g., triacylglycerols, polar lipids, wax esters).

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  • This module is the eighth in a series of Extension materials designed to provide Extension agents, Certified Crop Advisers (CCAs), consultants, and producers with pertinent information on nutrient management issues. To make the learning ‘active,’ and to provide credits to Certified Crop Advisers, a quiz accompanies this module.

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  • The world ocean has somewhere between 10 000 and 100 000 seamounts more than 1 km tall and as many as 1 000 000 features over 100 m tall. These are some of the least understood habitats on the planet. Large seamounts, particularly those close to or within the photic zone, support and attract rich biotic communities and are important for the status of marine food webs and biodiversity. Intensive boom-and-bust fi sheries have depleted fi sh populations and damaged or destroyed associated benthic communities.

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  • Mass media still accounts for the bulk of ad spending: television (44.1 percent), magazines (21.1 percent), newspapers (17.2 percent), radio (7.0 percent), and outdoor (2.6 percent). The internet accounts for 8 percent. Internet advertising has grown each year, while allocations to other media categories have consistently declined. The internet accounts for 20 percent of consumer media consumption. Given the current allocation of 8 percent of ad spending, continued growth in online advertising is practically a certainty. Online advertising (Web 1.

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  • As you learned above, probably the most important function of computers is their ability to store large amounts of data. The World Wide Web is probably the largest source of information and is available to anyone in the world with a computer and Internet connection. By the end of 2006, there were well over 120 million users connected to some 7 million websites. However, a good portion of information stored on computers is sensitive and critical, and if lost or accessed by the wrong person, could potentially create tremendous personal anxiety and global problems.

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  • This book owes its inception to my fascination with the natural microcosms that are water-filled tree holes and, subsequently, the broader class of plant container habitats we call phytotelmata. That fascination was born, first, in a Somerset woodland, when my fellow undergraduate Alastair Sommerville pointed out to me a massive stump hole, commenting that such places were both entomologically special and of great potential as objects of ecological study.

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