The shape of life: how much is written in stone?

Summary Considering the enormous diversity of living organisms, representing mostly untapped resources for studying ecological, ontogenetic and phylogenetic patterns and processes, why should evolutionary biologists concern themselves with the remains of animals and plants that died out tens or even hundreds of millions of years ago? The reason is that important new insights into some of the most vexing evolutionary questions are being revealed at the interfaces of palaeontology, developmental biology and molecular biology. Attempts to synthesise information from these disciplines, however, often encounter their greatest hurdles in considerations of the radiation of the Metazoa. Ongoing challenges relate to the origins of body plans, the relationships of the metazoan phyla and the timing of major evolutionary radiations. Palaeontology not only has its own unique contributions to the study of evolutionary processes, but provides a lynchpin for many of the emerging techniques

A modern assessment of Ordovician chitinozoans from the Shelve and Caradoc areas, Shropshire, and their significance for correlation

New chitinozoan data are presented from the classical section along the Onny River in the type Caradoc area, and from the deeper-water sections in the Shelve area, including the former British candidate GSSP for the base of the Upper Ordovician Series. The rich and well-preserved chitinozoan fauna of the Onny River has been a standard for 40 years, but new data revise some of the identifications. The assemblages are now attributed to biozones that are more readily applicable for international cor relation. The main part of the section can be inter preted as belonging to the originally Baltoscandian Spinachitina cervicornis Biozone, although this is uncertain in the lower part. Within this biozone, the Fungochitina actonica Subzone has been defined. The Onny Formation at the top of the section is equated with the Acanthochitina latebrosa–Ancyrochitina onniensis Biozone; contrary to earlier reports, Acanthochitina barbata is absent. The Lower Wood Brook and Spy Wood Brook section from the Shelve Inlier yielded a great number of moderately to well-preserved chitinozoans, but a low-diversity assemblage. Their ranges have been neatly positioned against the well-known graptolite stratigraphy in the area. A local Eisenackitina rhenana Biozone? has been recognized, allowing us to suggest some international cor relations

Compilation and Network Analyses of Cambrian Food Webs

A rich body of empirically grounded theory has developed about food webs—the networks of feeding relationships among species within habitats. However, detailed food-web data and analyses are lacking for ancient ecosystems, largely because of the low resolution of taxa coupled with uncertain and incomplete information about feeding interactions. These impediments appear insurmountable for most fossil assemblages; however, a few assemblages with excellent soft-body preservation across trophic levels are candidates for food-web data compilation and topological analysis. Here we present plausible, detailed food webs for the Chengjiang and Burgess Shale assemblages from the Cambrian Period. Analyses of degree distributions and other structural network properties, including sensitivity analyses of the effects of uncertainty associated with Cambrian diet designations, suggest that these early Paleozoic communities share remarkably similar topology with modern food webs. Observed regularities reflect a systematic dependence of structure on the numbers of taxa and links in a web. Most aspects of Cambrian food-web structure are well-characterized by a simple “niche model,” which was developed for modern food webs and takes into account this scale dependence. However, a few aspects of topology differ between the ancient and recent webs: longer path lengths between species and more species in feeding loops in the earlier Chengjiang web, and higher variability in the number of links per species for both Cambrian webs. Our results are relatively insensitive to the exclusion of low-certainty or random links. The many similarities between Cambrian and recent food webs point toward surprisingly strong and enduring constraints on the organization of complex feeding interactions among metazoan species. The few differences could reflect a transition to more strongly integrated and constrained trophic organization within ecosystems following the rapid diversification of species, body plans, and trophic roles during the Cambrian radiation. More research is needed to explore the generality of food-web structure through deep time and across habitats, especially to investigate potential mechanisms that could give rise to similar structure, as well as any differences

Charles Darwin: The scientist as hero

Hi ha poques figures que han assolit la importància cultural de Charles Darwin. Aquí tenim un científic a qui nosaltres (els altres científics) ens agradaria posar com a model: era una bona persona, creatiu i que estava a favor d'un avenç científic que pogués ser entès per tothom. La seva idea de l'origen comú era senzilla i realment va canviar la manera que veiem el món; de la mateixa manera que el coneixement dels gens i el codi genètic ha transformat biologia i medicina. Aquest article explora a la figura de Darwin, i la història de vida més específicament. Som conscients que el món evoluciona, i vida amb ell. La història del canvi des d'un món dominat per procariotes (sense nuclis organitzats) fa 3500 milions d'anys a l'aparició d'eucariotes amb nuclis i d'organismes sexualment diferenciats fa aproximadament 1300 milions d'anys, i després a organismes complexos de gran mida 700 milions d'anys més tard, és tant un homenatge a la intuïció Darwiniana com una història amb desemvolupaments nous que exploraré.There are few figures that have attained quite the cultural significance of Charles Darwin. Here is the scientist as we (our fellow scientists) would like the creature to be portrayed: he was a good human being as well as a creative one and he stood for a scientific advance that could be grasped by everyone. His idea of common descent is a simple one and it really did change the way we see the world; just as knowledge of genes and the genetic code really has transformed biology and medicine. This article takes a look at Darwin and the history of life more specifically. It has become clear that the world evolved, and life with it. The story of the change from a world dominated by prokaryotes (lacking organised nuclei) at 3.5 billion years ago to the appearance of eukaryotes with nuclei and of sexually differentiated organisms at about 1300 million years ago, and thence to complex organisms that achieved large size 700 million years later is both a tribute to Darwinian intuition and a story with new developments which I will explore

Stratigraphy, palaeoecology and trilobite faunas of the Valhatlfonna formation, Ny Friesland, Spitsbergen.

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