Katherine J. Knierim

Two-Stage Exams Improve Student Learning in an Introductory Geology Course: Logistics, Attendance, and Grades

ABSTRACT Two-stage exams—where students complete part one of an exam closed book and independently and part two is completed open book and independently (two-stage independent, or TS-I) or collaboratively (two-stage collaborative, or TS-C)—provide a means to include collaborative learning in summative assessments. Collaborative learning has been shown to have positive benefits, including increased student engagement and learning. To try to improve student learning, as measured by improvement in exam scores, two sections of introductory geology were taught using two-stage exams. It was hypothesized that class scores would be higher for semesters using two-stage exams—whether part two was TS-C or TS-I—than for semesters using traditional (T) exams. The median attendance rate was approximately 67% for all testing methods and was significantly greater when exams were TS-C (69%) rather than TS-I (53%). The class score was significantly greater during semesters when exams were TS-C (81%) but was not significantly different between T and TS-I semesters. To assess individual student learning over time, part one of the first exam and part one of the comprehensive final exam were compared. Across the F and D grade ranges, improvement on individual exam scores was significantly greater for the TS-C semester than for the TS-I and T semesters. Student learning, as measured by individual exam scores, improved due to the use of TS-C exams. The improvement in class scores due to the collaborative portion of two-stage exams was independent of increased attendance rates, greater for the lower-achieving students, and not observable if part two of the exam was completed as a take-home exam (TS-I).

Using stable isotopes of carbon to investigate the seasonal variation of carbon transfer in a northwestern Arkansas cave

Stable-isotope analyses are valuable in karst settings, where characterizing biogeochemical cycling of carbon along groundwater flow paths is critical for understanding and protecting sensitive cave and karst water resources. This study quantified the seasonal changes in concentration and isotopic composition (dC) of aqueous and gaseous carbon species—dissolved inorganic carbon (DIC) and gaseous carbon dioxide (CO2)—to characterize sources and transfer of these species along a karst flow path, with emphasis on a cave environment. Gas and water samples were collected from the soil and a cave in northwestern Arkansas approximately once a month for one year to characterize carbon cycling along a conceptual groundwater flow path. In the soil, as the DIC concentration increased, the isotopic composition of the DIC became relatively lighter, indicating an organic carbon source for a component of the DIC and corroborating soil DIC as a proxy for soil respiration. In the cave, a positive correlation between DIC and surface temperature was due to increased soil respiration as the organic carbon signal from the soil was transferred to the cave environment via the aqueous phase. CO2 concentration was lowest in the cave during colder months and increased exponentially with increasing surface temperature, presumably due to higher rates of soil respiration during warmer periods and changing ventilation patterns between the surface and cave atmosphere. Isotopic disequilibrium between CO2 and DIC in the cave was greatest when CO2 concentration was changing during November/ December and March/April, presumably due to the rapid addition or removal of gaseous CO2. The isotopic disequilibrium between DIC and CO2 provided evidence that cave CO2 was a mixture of carbon from several sources, which was mostly constrained by mixture between atmospheric CO2 and soil CO2. The concentration and isotopic composition of gaseous and aqueous carbon species were controlled by month-to-month variations in temperature and precipitation and provided insight into the sources of carbon in the cave. Stable carbon isotope ratios provided an effective tool to explore carbon transfer from the soil zone and into the cave, identify carbon sources in the cave, and investigate how seasonality affected the transfer of carbon in a shallow karst system.

Hydrogeology and hydrologic conditions of the Ozark Plateaus aquifer system

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The Ozark Plateaus Regional Aquifer Study—Documentation of a groundwater-flow model constructed to assess water availability in the Ozark Plateaus

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