Paul J. Bischoff

An Analysis of Knowledge Structure, Diversity and Diagnostic Abilities Among Pre-Service Science Teachers Within the Domain of Oxidation and Reduction Chemistry

The purpose of this study was to investigate the development of preservice science teachers’ knowledge structures in the domain of oxidation and reduction chemistry. Knowledge structures were elicited through video-recorded semi-structured interviews before and after the unit of instruction, and analyzed using a visual flow map representation. Paralleling these interviews, the preservice teachers were tasked with diagnosing middle school students’ scientific understandings. Data analyzed quantitatively and qualitatively showed large variation in knowledge structure complexity across the preservice teachers, strong correlations between measures of knowledge structure and diversity (as defined by the Shannon Wiener diversity index), and the development of more balanced knowledge structure representations. For most preservice teachers, their diagnostic scores of the middle school students showed a small increase.

Seasonal abundances of naked amoebae in biofilms on shells of zebra mussels (Dreissena polymorpha) with comparative data from rock scrapings.

ABSTRACT. In North America, zebra mussels (Dreissena polymorpha) are notoriously known as invasive species. The abundance of naked amoebae sampled from the shells of zebra mussels was compared with abundances from rock scrapings at approximately monthly intervals for 1 year. The sites were 2 km apart along the same shoreline. No significant difference in abundance of naked amoebae (F=1.44; P≤0.270) was detected for the two sampling sites. The combined data showed a minimum density of naked amoebae in winter, followed by peaks in early spring. The percent encysted increased from a low of 1% in the summer to 80% in early winter.

Winter Abundances of Naked Amoebae in the Soil System of the Invasive Species Japanese Knotweed (Fallopia japonica) with Comparative Data from Adjacent Sites

Among the most prolific invasive plant species posing threats to the ecological balance of ecosystems in North America and Europe is Japanese knotweed (Fallopia japonica). In order to identify the potential role of protists in the invasive capacity of Japanese knotweed the winter abundances of naked amoebae in soils from three roadside thickets of Japanese knotweed were compared to nearby non-invaded sites. Japanese knotweed soils had higher abundances (t = 5.43, df, 16, p < 0.001) of amoebae than comparison sites. This is one of the first studies to document higher abundances of soil naked amoebae associated with an invasive plant, and may indicate more generally that below-ground abundances of amoebae can promote soil fertility and support the successful adaptation and expansion of some invasive plant species. Moreover, analysis of encysted vs. trophic forms of naked amoebae in the winter soil, provided evidence of freezeresistant, amoeba resting cells in soil samples from the natural environment in support of prior findings that were based solely on laboratory experimental evidence. Overall, high densities of naked amoebae in the winter soils of Japanese knotweed, some as resting cells capable of forming rapidly activated trophic stages, likely increase soil fertility and strengthen the species’ invasive capacity.

Abundances of Naked Amoebae and Macroflagellates in Central New York Lakes: Possible Effects by Zebra Mussels

Summary. Zebra mussels (Dreissena polymorpha) are bivalve mollusks that have invaded and altered the ecology of many North American lakes and rivers. To identify possible ecological effects of zebra mussels on naked amoebae, this study compared abundances of sediment and water column naked amoebae in shallow water zones of four lakes with and four lakes without zebra mussels. Additional data was collected on the density of macroflagellates. Although no statistically significant difference in naked amoebae density was found, higher ratios of sediment to water column naked amoebae abundances in zebra mussel lakes were observed due to increased naked amoebae abundances in the sediments. However, we did not observe a concomitant decrease in water column naked amoebae abundances. Flagellate abundances revealed no significant differences between the two lake types. Taken together, the data show that naked amoebae and flagellates thrive in shallow water zones of zebra mussel lakes and that the filter feeding activities of zebra mussels and reported reduced water column protists abundances may be offset by the flocculation of protists from the rich zebra mussel colonies.