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Monard C.,Swedish University of Agricultural Sciences | Gantner S.,Swedish University of Agricultural Sciences | Gantner S.,Uppsala University | Gantner S.,Leibniz Institute for Science and Mathematics Education IPN | Stenlid J.,Swedish University of Agricultural Sciences
FEMS Microbiology Ecology | Year: 2013

The shorter reads generated by high-throughput sequencing has led to a focus on either the ITS1 or the ITS2 sublocus in fungal diversity analyses. Our study aimed to determine how making this choice would influence the datasets obtained and our vision of environmental fungal diversity. DNA was extracted from different environmental samples (water, sediments and soil) and the total internal transcribed spacer (ITS) locus was amplified. 454-sequencing was performed targeting both ITS1 and ITS2. No significant differences in the number of sequences, operational taxonomic units (OTUs) and in the dominant OTUs were detected but less diversity was observed in the ITS2 dataset. In the soil samples, differences in the fungal taxonomic identification were observed, with more Basidiomycota in the ITS1 dataset and more Ascomycota in the ITS2 dataset. Only one-third of the OTUs were detected in both datasets which could be due to (1) more short sequences removed in the ITS2 dataset, (2) different taxonomic affiliation depending on the sublocus used as BLASTn query and/or (3) selectivity in how a primer amplifies the true community. Although ITS1 and ITS2 datasets led to similar results at the fungal community level, for further in-depth diversity analysis this study suggests the analysis of both ITS regions, as they provided different information and were complementary. © 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved. Source

Taskin V.,Leibniz Institute for Science and Mathematics Education IPN | Bernholt S.,Leibniz Institute for Science and Mathematics Education IPN | Parchmann I.,Leibniz Institute for Science and Mathematics Education IPN
Chemistry Education Research and Practice | Year: 2015

Chemical representations play an important role in helping learners to understand chemical contents. Thus, dealing with chemical representations is a necessity for learning chemistry, but at the same time, it presents a great challenge to learners. Due to this great challenge, it is not surprising that numerous national and international studies have shown that students have remarkable difficulties. Since most of the studies regarding chemical representations have focused on investigating high-school students' knowledge so far, little is known about university students' and especially student teachers' knowledge. The latter group is additionally challenged by the necessity of learning how to transform their own knowledge in order to teach chemical representations to their prospective students. Given this as a starting point, a paper-and-pencil test with 19 items in both semi-open and closed format was developed to investigate the extent of student teachers' knowledge of chemical representations. The present paper describes the design, validation, and psychometric analysis of this test instrument - the so-called Chemical Representations Inventory (CRI). The CRI includes a variety of chemical representations and chemical contents on both high-school and university level. Both classical test theory and Rasch modelling were used for the analysis. In addition, a qualitative analysis was performed, and factors which possibly influence the item difficulty were identified. Even though the CRI was originally developed for a sample of student teachers, it can also be used to measure chemistry students' knowledge on a basic level. This journal is © The Royal Society of Chemistry. Source

Hadenfeldt J.C.,Leibniz Institute for Science and Mathematics Education IPN | Bernholt S.,Leibniz Institute for Science and Mathematics Education IPN | Liu X.,State University of New York at Buffalo | Neumann K.,Leibniz Institute for Science and Mathematics Education IPN | Parchmann I.,Leibniz Institute for Science and Mathematics Education IPN
Journal of Chemical Education | Year: 2013

Helping students develop a sound understanding of scientific concepts can be a major challenge. Lately, learning progressions have received increasing attention as a means to support students in developing understanding of core scientific concepts. At the center of a learning progression is a sequence of developmental levels reflecting an idealized progression toward understanding a particular core concept. This sequence is supposed to serve as a basis for designing instruction that can foster learning as well as assessments that can monitor students' progression. So-called ordered multiple-choice (OMC) items have recently been suggested as a simple and effective way of assessing students' level of understanding of a core concept. This article details our efforts in developing an instrument for assessing students' understanding of the structure and composition of matter based on OMC items. Ten OMC items were developed and administered to a sample of N = 294 students in grades 6-12. Rasch analysis was used to investigate instrument functioning and to determine linear measures of person abilities and item difficulties. In addition to the OMC items, students were administered corresponding open-ended items in order to investigate the validity of the results obtained through the OMC items. Our findings suggest assessing students' understanding of scientific concepts through OMC items is indeed quite worthwhile and should be subject to further research. © 2013 The American Chemical Society and Division of Chemical Education, Inc. Source

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