628 research outputs found

    Methods of quantitative and qualitative analysis of bird migration with a tracking radar

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    Methods of analyzing bird migration by using tracking radar are discussed. The procedure for assessing the rate of bird passage is described. Three topics are presented concerning the grouping of nocturnal migrants, the velocity of migratory flight, and identification of species by radar echoes. The height and volume of migration under different weather conditions are examined. The methods for studying the directions of migration and the correlation between winds and the height and direction of migrating birds are presented


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    The Coexistence of Hosts with Different Abilities to Discriminate against Cheater Partners: An Evolutionary Game-Theory Approach

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    Evolutionary theory predicts that mutualisms based on the reciprocal exchange of costly services should be susceptible to exploitation by cheaters. Consistent with theory, both cheating and discrimination against cheaters are ubiquitous features of mutualisms. Several recent studies have confirmed that host species differ in the extent that they are able to discriminate against cheaters, suggesting that cheating may be stabilized by the existence of susceptible hosts (dubbed “givers”). We use an evolutionary game-theoretical approach to demonstrate how discriminating and giver hosts associating with mutualist and cheater partners can coexist. Discriminators drive the proportion of cheaters below a critical threshold, at which point there is no benefit to investing resources into discrimination. This promotes givers, who benefit from mutualists but allow cheater populations to rebound. We then apply this model to the plant-mycorrhizal mutualism and demonstrate it is one mechanism for generating host-specific responses to mycorrhizal fungal species necessary to generate negative plant-soil feedbacks. Our model makes several falsifiable, qualitative predictions for plant-mycorrhizal population dynamics across gradients of soil phosphorus availability and interhost differences in ability to discriminate. Finally, we suggest applications and limitations of the model with regard to coexistence in specific biological systems


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    This study sought to determine the concurrent validity between course grades and performance on standardized test in classrooms where nonachievement factors were separated from the reporting of achievement factors in a teacher's grading system.   In reviewing the literature, multiple studies indicated that the greatest culprit in the distortion of grades was the inclusion of non-achievement factors (e.g. penalties for late work, extra credit for bringing in supplies, effort or lack thereof, attendance). Therefore, this study examined the relationship between teachers' grading practices and the correlation established between their students' grades and their performance on the standardized test.   High school science teachers from two comparable schools were selected to participate in this study. They were selected because they claimed to have a grading system that separated nonachievement factors from achievement factors and they taught courses that culminated in a standardized assessment. The teachers participating in this study were asked to complete a survey to assess how well their grading system aligned with what measurement experts recommended, with regards to the removal of nonachievement factors. Results from each teacher's survey were compared to the correlations determined between his/her student's grades and performance on the standardized assessment.   Findings for all teachers but one revealed a strong relationship between students' grades and their performance on the standardized assessment. However, when looking at whether or not a teacher's grading system had an impact on the strength of the correlation, it was determined that no association of significance existed.    The outcomes of this study furthered the research on effective grading systems. Based on the findings, there continues to be a strong need for effective professional development on how to establish a valid and reliable grading system. Furthermore, issues on how to build an effective assessment were also revealed. Further studies addressing either topic are warranted.  Ed.D

    Classification and identification of Pfiesteria and Pfiesteria-like species

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    Dinoflagellates can be classified both botanically and zoologically; however, they are typically put in the botanical division Pyrrhophyta. As a group they appear most related to the protistan ciliates and apicomplexans at the ultrastructure level. Within the Pyrrhophyta are both unarmored and armored forms of the dominant, motile flagellated stage. Unarmored dinoflagellates do not have thecal or wall plates arranged in specific series, whereas armored species have plates that vary in thickness but are specific in number and arrangement. In armored dinoflagellates, the plate pattern and tabulation is a diagnostic character at the family, subfamily, and even genus levels. In most cases, the molecular characterization of dinoflagellates confirms the taxonomy on the basis of external morphology; this has been demonstrated for several groups. Together, both genetic and morphological criteria are becoming increasingly important for the characterization, separation, and identification of dinoflagellates species. Pfiesteria and Pfiesteria-like species are thinly armored forms with motile dinospore stages characterized by their distinct plate formulae. Pfiesteria piscicida is the best-known member of the genus; however, there is at least one other species. Other genetically and morphologically related genera, now grouped under the common names of Lucy, Shepherd\u27s crook, and cryptoperidiniopsoid, are being studied and described in separate works. All these other heterotrophic dinoflagellate groups, many of which are thought to be benign, co-occur in estuarine waters where Pfiesteria has been found