Gastric teeth of some thoracotreme crabs and their contribution to the brachyuran phylogeny

The gastric teeth of three ocypodoid species were investigated using scanning electron microscopy, and the morphological results were discussed with respect to the known food preferences. The species were chosen in particular because of contrasting ideas about their relationships within the Thoracotremata. For the genera Heloecius, Dotilla, Mictyris, and “Uca” (s. str.), we find a specific correlation of the gastric teeth with the suspension feeding. The lateral gastric teeth of Uca have no prominent lateral teeth cusps, and most of their teeth surface consists of transverse comb‐like lamellae. However, this possible food adaptation does not exclude the usability of specific teeth characters to distinguish species of suspension feeders. The closer relationship of the Dotillidae to grapsoid lines of gecarcinid or sesarmid crabs suggested by molecular data is not supported by the gastric teeth. For the genus Ucides, we found several characters that distinguish Ucides from the remaining ocypodoid genera Heloecius, Dotilla, Mictyris, and “Uca.” In particular, the structures of the lateral and the dorsomedian teeth show some similarities to genera of the Gecarcinidae and Sesarmidae. Our results suggest that foregut characters can be used for phylogenetic analyses. J. Morphol. 2011. © 2011 Wiley‐Liss, Inc.     

Students’ conceptions of the carbon cycle: identifying and interrelating components of the carbon cycle and tracing carbon atoms across the levels of biological organisation

This study investigates students’ conceptions of the carbon cycle with regard to the components they believe to be relevant to the carbon cycle, how they interrelate these components, the ways in which they trace carbon atoms, and the different levels of biological organisation they consider when doing so. A total of 142 students aged 13–16 years (grades 8–10) participated in the study. A total of 130 students completed the diagnostic task, and an additional 12 students completed both the diagnostic task and were interviewed. The primary results show that the students identified few components of the carbon cycle, tended to trace carbon atoms exclusively at the level of the organism, and had difficulties identifying organic carbon compounds, especially during processes in which carbon compounds are transformed. Considering the main educational implications, we recommend using an instructional strategy that traces carbon atoms across the different levels of biological organisation whilst connecting fragmented knowledge by integrating knowledge from physiology, biochemistry and ecology when teaching the carbon cycle.     

Considering the levels of biological organisation when teaching carbon flows in a terrestrial ecosystem

ABSTRACT

Students often have misconceptions about terrestrial carbon flows and there is a lack of coherence in students’ explanations regarding the different levels of biological organisation at which these processes occur. In this study, problem-based teaching materials on the topic of terrestrial carbon flows were developed and tested with 15 students 18–19 years old (grade 12) using a pre/post-test design. Students focused on specific carbon flows in an ecosystem at the macro level (e.g. CO₂ fixation and heterotrophic respiration) including specific related concepts at the micro level (e.g. photosynthesis and cellular respiration). The findings indicate that the teaching materials improved the students’ understanding of terrestrial carbon flows and their ability to reason across the different levels of biological organisation. On the basis of these findings, implications for teaching terrestrial carbon flows in biological education are discussed.     

Comparative statistical studies on the physical anthropology of the early medieval period (500–1000 A.D.)

Continuing previous studies on preceding periods a total of 194 population samples of this period, described by 10 skull measurements of males only, are analysed by Penrose's generalized distance.The cluster analysis includes those 157 samples in which the number of individuals was not less than 10 for any measurement. As in the earlier periods the dendrogram reveals a west cluster and an east cluster, but the differences between them begin to blur due to a large intermediate group with very variable distances. In the east cluster a Krimea subcluster and a Turcotatar subcluster can be distinguished. The west cluster reveals extremely low distances. In the intermediate group there is a small Baltic subcluster known already from the Roman period, and an Avar subcluster which, however, comprises only a part of the Hungarian samples of the Avar period.In an additional cluster analysis larger ethnic and geographical groups are compared and show clear west-east differences. Teutonic and Slav groups are slightly better separated than before.The east cluster differs from the west cluster in the same direction as in the earlier periods. The east is mainly characterized by the larger breadth measurements. On the basis of the available variables it is not possible to decide what part is played by a mongoloid component. The variables of the middle group are also intermediate between those for east and west.In the east, there is a continuing diachronic trend towards a decrease in skull length and height, and also an increase in skull width. This does not hold for the west possibly as the trend has been changed because western Europe is represented only by Teutons, i.e. by non-aboriginal groups. The population changes in the migration period may also explain why the diachronic trend towards a decrease in the mean distances has reversed in several regions. For instance, in southern Russia the increasing differences are clearly attributable to the immigration of Turcotatar groups.     

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Phosphoenolpyruvate Carboxylase Purified from Leaves of C3, C4, and C3-C4 intermediate species of Alternanthera: Properties at Limiting and Saturating Bicarbonate

Photosynthetica - Phosphoenolpyruvate carboxylase (PEPC) was purified from leaves of four species of Alternanthera differing in their photosynthetic carbon metabolism: Alternanthera sessilis (C3),...     

A classification of European skulls from three time periods

We analyze the taxonomic structure of European populations at three time periods, the Early Middle Ages, the Late Middle Ages and the Recent Period. The data consist of sample means for 10 cranial variables based on 137, 108, and 183 samples for the three periods. Clustering by standard numerical taxonomic procedures reveals that the data are represented only poorly as hierarchic classifications. The clusters form significant and moderately strong associations with an arrangement of the samples by regions (geography) and by language family. Whereas during the early period, language family showed a stronger association with clusters based on cranial morphology, in the recent populations these clusters correspond better with geography than with language. Ordinations of these populations by means of nonmetric multidimensional scaling shows the continuity of the taxonomic structure at all three periods. Only a few populations are outliers. The relations between phenetic distances (cranial morphology), geography, and language are examined by means of multiple Mantel tests. At all three periods geography is correlated somewhat more strongly with phenetics than is language affiliation, but the correlation with the latter increases with time. When the data are pooled over the three periods, the populations tend to group by language affiliation more than they do by period. Ordination of the pooled data reveals language patterns rather than patterns due to period, showing strong shifts in cranial measurements through time. These analyses show that while there is no clear-cut taxonomic structure in European populations that would justify the traditional classifications based on the crania, there are significant and important associations with both language affiliation, geography, and time period, in this order. These patterns are likely to have become established through the migration and subsequent expansion of populations into their areas of occupation during the time interval studied rather than by geographic differentiation in situ.