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JAN BERGSTRÖM 《Zoologica scripta》1986,15(3):189-200
Within their limits of resolution, different methods to reveal biochemical evolution appear to give reliable results where they can be controlled, as in the case of the Vertebrata. Compounds such as cytochrome c, SS rRNA and globins yield closely comparable results, which further strengthens the reliability. When the methods are applied to biochemical data from as many metazoan phyla as possible, the result is a phylogenetic tree which contrasts in certain respects with phylogenetic trees based on comparative zoology data. Important conclusions seem to include the following: (1) many metazoan phyla appear to have branched off from a shared, very conservative spiralian/protostome ancestral stock through the adoption of basically new feeding and locomotory strategies; (2) this origination makes it almost impossible to use a comparative zoology approach to solve problems of interphylum (in contrast to intraphylum) affinities, as similarities tend to be due only to shared derived Characters and similar life strategies, while dissimilarities are due to different basic life strategies; (3) protostome characters constitute a synapomorphy for triploblastic metazoans, and where absent they are secondarily lost, which means that protostome and deuterostome characters are irregularly distributed and mixed; (4) true deuterostomes form a sister group of the Mollusca, and they are only a top branch of the evolutionary tree. 相似文献
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We describe and illustrate Coccinia pwaniensis Holstein from eastern Tanzania and southeast Kenya, and C. samburuensis Holstein from the Samburu area in Kenya. The new species were already recognised by Charles Jeffrey in 1967 and are now known
from eight and four collections, respectively. Ongoing monographic work also revealed three new synonyms and the need for
a new combination, Coccinia heterophylla (Hook. f.) Holstein. 相似文献
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Rodrick Wallace 《Comptes rendus biologies》2014,337(1):1-5
The ‘Cambrian explosion’ 500 Myr ago saw a relatively sudden proliferation of organism Bauplan and ecosystem niche structure that continues to haunt evolutionary biology. Here, adapting standard methods from information theory and statistical mechanics, we model the phenomenon as a noise-driven phase transition, in the context of deep-time relaxation of current path-dependent evolutionary constraints. The result is analogous to recent suggestions that multiple ‘explosions’ of increasing complexity in the genetic code were driven by rising intensities of available metabolic free energy. In the absence of severe path-dependent lock-in, ‘Cambrian explosions’ are standard features of blind evolutionary process, representing outliers in the ongoing routine of evolutionary punctuated equilibrium. 相似文献