نتایج جستجو برای: extinction of rare species
تعداد نتایج: 21217683 فیلتر نتایج به سال:
The international market for luxury goods puts pressure on many wildlife species, with potentially irreversible consequences for many of them. Although classical economic theory suggests that trade alone would not drive a rare species to extinction, in practice numerous species are being threatened by overexploitation. This is for example the case for sturgeons, exploited for their caviar, of w...
The statistical properties of an ecosystem composed of species interacting via pairwise, random interactions and deterministic, concentration limiting self-interactions are studied analytically with tools of equilibrium statistical mechanics of disordered systems. Emphasis is given to the effects of externally induced extinction of a fixed fraction of species at the outset of the evolutionary p...
The statistical properties of an ecosystem composed of species interacting via pairwise, random interactions and deterministic, concentration limiting self-interactions are studied analytically with tools of equilibrium statistical mechanics of disordered systems. Emphasis is given to the effects of externally induced extinction of a fixed fraction of species at the outset of the evolutionary p...
PREMISE OF THE STUDY Differences in rarity among species can be caused by adaptation to local conditions along with correlated evolution in characters that limit geographic range size. For this kind of divergence, the resulting species differ in their ability to thrive in varying environments. Because rare species are more prone to extinction than widespread species, trade-offs in life history ...
In this study, pollination of 6 herbaceous astragalus species including three rare herbaceous vegetative forms (As. Caraganae, As. Heterophyllus and As. Holopsilus) and three common herbaceous vegetative forms (As. Angustiflorus, As. Curvirostris and As. Effusus) and 6 shrub astragalus species includes three rare shrub vegetative forms (As. Cephalanthus, As. Camphylanthus and As. Cemerinus) and...
We analysed field-collected quantitative data of benthic marine molluscs across the Cretaceous-Palaeogene boundary in Patagonia to identify patterns and processes of biodiversity reconstruction after the end-Cretaceous mass extinction. We contrast diversity dynamics from nearshore environments with those from offshore environments. In both settings, Early Palaeogene (Danian) assemblages are str...
abstract part one: the electrode oxidation potentials of a series of eighteen n-hydroxy compounds in aqueous solution were calculated based on a proper thermodynamic cycle. the dft method at the level of b3lyp-6-31g(d,p) was used to calculate the gas-phase free energy differences ,and the polarizable continuum model (pcm) was applied to describe the solvent and its interaction with n-hydroxy ...
that are in danger of becoming extinct or have already done so. It’s remarkable as the combined effort of hundreds of thousands of people, many of them amateurs, to compile data on the status of their favorite taxa. For amphibians, we know that there were 1437 species described by taxonomists before 1900. Of these, 18 are either extinct or presumed extinct. After 1900, taxonomists described 496...
How many species are likely as-yet unknown to science? Even in relatively well-known groups, there may be substantial numbers of such species. It seems likely that these unknown species will be rare and threatened with extinction. Indeed, science may not discover them before they go extinct. We address these issues for a sample of endemic flowering plants and three vertebrate groups: amphibians...
abstract al- muntazam by ibn al -jawzi is one of the greatest the book ancient book of texts on history of islam in the 6th century.it is very important one;because of including rare reports which are not found any where.in addition to historical reports,his outlook , in which embodies information on mythologies, milal wa nihal (sects and creeds), geography, and political, social and religiou...
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