نتایج جستجو برای: extinction of rare species
تعداد نتایج: 21217683 فیلتر نتایج به سال:
in this study, a simple, rapid and selective method was developed for the determination of dexamethasone. the proposed method is based on inhibitory effect of dexamethasone on the oxidation of orange-g by bromate in sulfuric acid media. the reaction was followed spectrophotometrically at 478.5 nm (?max). under optimum experimental conditions, (72.6 ?mol l-1 of orange-g, 0.76 mol l-1 of h2so4, 0...
Current theories about mechanisms promoting species co-existence in diverse communities assume that species only interact ecologically. Species are treated as discrete evolutionary entities, even though abundant empirical evidence indicates that patterns of gene flow such as selfing and hybridization frequently occur in plant and animal groups. Here, we allow mating behavior to respond to local...
There is broad consensus that the diversity of functional traits within species assemblages drives several ecological processes. It is also widely recognized that rare species are the first to become extinct following human-induced disturbances. Surprisingly, however, the functional importance of rare species is still poorly understood, particularly in tropical species-rich assemblages where th...
Theory and empirical evidence have long suggested that some species are extremely vulnerable to extinction because they have combinations of extinction promoting traits. However, ecologists have not considered whether the form of the relationship between traits is additive (not synergistic) or nonadditive (synergistic). We looked at how traits and their interactions were related to the differen...
مراتع حدود نیمی از خشکی های جهان را در بر دارند و پوشش گیاهی آن در نتیجه تأثیر متقابل محیط و موجودات زنده به وجود آمده است و به عنوان یک اکوسیستم طبیعی مدیریت می شوند. علاوه بر مراتع، راه ها در عصر حاضر نیز از اجزا مهم و زیرساخت های اصلی زندگی نوین و توسعه کشورها به شمار می روند. جاده ها ساخته دست بشر هستند و جوامع گیاهی کنار جاده تحت تأثیر ساخت و ساز قرار دارند. پوشش "رودرال" به مجموعه ای از پ...
The extinction of species is not normally considered an important element of neodarwinian theory, in contrast to the opposite phenomenon, speciation. This is surprising in view of the special importance Darwin attached to extinction, and because the number of species extinctions in the history of life is almost the same as the number of originations; present-day biodiversity is the result of a ...
Extinction of an epidemic or a species is a rare event that occurs due to a large, rare stochastic fluctuation. Although the extinction process is dynamically unstable, it follows an optimal path that maximizes the probability of extinction. We show that the optimal path is also directly related to the finite-time Lyapunov exponents of the underlying dynamical system in that the optimal path di...
چکیده مورچهها با حمایت از شپشکها در مقابل دشمنان طبیعی، میتوانند برنامههای کنترل بیولوژیک آنها را مختل نمایند. طی سالهای 1389 و 1390 با نمونهبرداری از باغات مرکبات شهرستانهای ساری و بهشهر، فون و فراوانی نسبی مورچههایِ همراه با شپشکها مورد مطالعه قرار گرفت. همچنین، تاثیر تراکمهای مختلف کاست کارگر گونهی santschi lasius turcicus بر میزان تغذیه و فراسنجههای واکنش تابعی حشرات ماده و لا...
Economic incentives to harvest a species usually diminish as its abundance declines, because harvest costs increase. This prevents harvesting to extinction. A known exception can occur if consumer demand causes a declining species' harvest price to rise faster than costs. This threat may affect rare and valuable species, such as large land mammals, sturgeons, and bluefin tunas. We analyze a sim...
environmental degradation all over the world is one of the three major concerns of the human being. depletion of fresh water sources on earth, ozone layer depletion, soil degradation, intensive farming, climate change and temperature increase, biodiversity loss, population increase, poverty, pollution, extinction of rare species, biological extinction and endangered species are the main environ...
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