منابع مشابه
Mechanisms of urodele limb regeneration
This review explores the historical and current state of our knowledge about urodele limb regeneration. Topics discussed are (1) blastema formation by the proteolytic histolysis of limb tissues to release resident stem cells and mononucleate cells that undergo dedifferentiation, cell cycle entry and accumulation under the apical epidermal cap. (2) The origin, phenotypic memory, and positional m...
متن کاملThe end-Permian extinction
The end Permian extinction was the greatest mass extinction of the Phanerozoic Era. It impacted marine and terrestrial plants and animals. Although the rate of the extinction has been controversial in the past, recent evidence suggests that the extinction progressed in two pulses approximately 5-12 million years apart. The second pulse of the extinction is marked by a sharp temperature spike an...
متن کاملThe Permian bacterium that isn't.
There is growing evidence for the presence of viable microorganisms in geological salt formations that are millions of years old. It is still not known, however, whether these bacteria are dormant organisms that are themselves millions of years old or whether the salt crystals merely provide a habitat in which contemporary microorganisms can grow, perhaps interspersed with relatively short peri...
متن کاملCurrent perspectives on the Permian–Triassic boundary and end-Permian mass extinction: Preface
The end-Permian mass extinction is now robustly dated at 252.6 ± 0.2 Ma (U–Pb) and the Permian–Triassic (P–T) GSSP level is dated by interpolation at 252.5 Ma. An isotopic geochronological timescale for the Late Permian–Early Triassic, based on recent accurate high-precision U–Pb single zircon dating of volcanic ashes, together with calibrated conodont zonation schemes, is presented. The durati...
متن کاملProlonged Permian Triassic ecological crisis recorded by molluscan dominance in Late Permian offshore assemblages.
The end-Permian mass extinction was the largest biotic crisis in the history of animal life, eliminating as many as 95% of all species and dramatically altering the ecological structure of marine communities. Although the causes of this pronounced ecosystem shift have been widely debated, the broad consensus based on inferences from global taxonomic diversity patterns suggests that the shift fr...
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ژورنال
عنوان ژورنال: The Biological Bulletin
سال: 1908
ISSN: 0006-3185,1939-8697
DOI: 10.2307/1536077