منابع مشابه
The Cambrian explosion
The sudden appearance of fossils that marks the so-called 'Cambrian explosion' has intrigued and exercised biologists since Darwin's time. In On the Origin of Species, Darwin made it clear that he believed that ancestral forms 'lived long before' their first fossil representatives. While he considered such an invisible record necessary to explain the level of complexity already seen in the foss...
متن کاملThe Cambrian Explosion
The Precambrian genesis plus Cambrian explosion scenario also implies a perplexing view of a major evolutionary radiation: a long period of cryptic speciation with increasing developmental complexity and anatomical sophistication, yet without substantial behavioural or ecological modification or diversification, followed by a sudden increase in morphological and ecological innovation. Page 1046...
متن کاملCambrian Lattices
For an arbitrary finite Coxeter group W , we define the family of Cambrian lattices for W as quotients of the weak order on W with respect to certain lattice congruences. We associate to each Cambrian lattice a complete fan, which we conjecture is the normal fan of a polytope combinatorially isomorphic to the generalized associahedron for W . In types A and B, we obtain, by means of a fiber-pol...
متن کاملTaking the Pulse of the Cambrian Radiation1
SYNOPSIS. The Cambrian radiation is that key episode in the history of life when a large number of animal phyla appeared in the fossil record over a geologically short period of time. Over the last 20 years, scientific understanding of this radiation has increased significantly. Still, fundamental questions remain about the timing of the radiation and also the tempo of evolution. Trilobites are...
متن کاملCambrian Hopf Algebras
Cambrian trees are oriented and labeled trees which fulfill local conditions around each node generalizing the conditions for classical binary search trees. Based on the bijective correspondence between signed permutations and leveled Cambrian trees, we define the Cambrian Hopf algebra generalizing J.-L. Loday and M. Ronco’s algebra on binary trees. We describe combinatorially the products and ...
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ژورنال
عنوان ژورنال: Nature
سال: 2011
ISSN: 0028-0836,1476-4687
DOI: 10.1038/471260a