نتایج جستجو برای: extinction of rare species
تعداد نتایج: 21217683 فیلتر نتایج به سال:
Almost 25% of skates and rays’ information worldwide is insufficient to assess their extinction risk. We reported the first seven confirmed records rough eagle ray (Aetomylaeus asperrimus) along north Pacific coast Costa Rica. These findings suggest that encounters with this species are rare, possibly associated oceanographic patterns. More needed make accurate assumptions on species’ abundance...
Among the different approaches to investigate in detail the extinction of population of rare species the Birth and Death process has given the simplest approach to settledown the solution. Here, an attempt is made to obtain the extinction probabilities and to generate a different levels of population sizes. A random quadtree method is footforth. We give the basic concepts and results used in th...
Species with narrow environmental niches typically have small geographic ranges. Small range size is, in turn, often associated with low local abundance. Together, these factors should mean that ecological specialists have very small total populations, putting them at high risk of extinction. But some specialized and geographically restricted species are ancient, and some ecological communities...
An ecological community's species diversity tends to erode through time as a result of stochastic extinction, competitive exclusion, and unstable host-enemy dynamics. This erosion of diversity can be prevented over the short term if recruits are highly diverse as a result of preferential recruitment of rare species or, alternatively, if rare species survive preferentially, which increases diver...
Extinction appears ubiquitously in many fields, including chemical reactions, population biology, evolution and epidemiology. Even though extinction as a random process is a rare event, its occurrence is observed in large finite populations. Extinction occurs when fluctuations owing to random transitions act as an effective force that drives one or more components or species to vanish. Although...
Virtually all plant and animal species that have ever lived on the earth are extinct. For this reason alone, extinction must play an important role in the evolution of life. The five largest mass extinctions of the past 600 million years are of greatest interest, but there is also a spectrum of smaller events, many of which indicate biological systems in profound stress. Extinction may be ep...
While disease-induced extinction is generally considered rare, a number of recently emerging infectious diseases with load-dependent pathology have led to extinction in wildlife populations. Transmission is a critical factor affecting disease-induced extinction, but the relative importance of transmission compared to load-dependent host resistance and tolerance is currently unknown. Using a com...
a frame semantic approach to the study of translating cultural scripts in salingers franny and zooey
the frame semantic theory is a nascent approach in the area of translation studies which goes beyond the linguistic barriers and helps us to incorporate cognitive and cultural factors to the study of translation. based on rojos analytical model (2002b), which centered in the frames or knowledge structures activated in the text, the present research explores the various translation problems that...
As species become very rare and approach extinction, purported sightings can stir controversy, especially when scarce management resources are at stake. We used quantitative methods to identify reports that do not fit prior sighting patterns. We also examined the effects of including records that meet different evidentiary standards on quantitative extinction assessments for four charismatic bi...
in vitro methods provide a variety of tools to supplement traditional methods for collection, propagation and preservation of endangered plant species. in this study, an efficient protocol was developed for in vitro propagation of colutea gifana, a rare and endangered plant species with limited reproductive capacity that grows in a narrow area of iran. single node explants were used for a serie...
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