This study assessed students' learning of evolution by natural selection within four different sections of an introductory biology course. Each section used a different combination of curricular materials (either traditional or historically rich materials) and instruction (either paired problem solving or traditional lecture). Students in the study completed pre-and postintervention evolution tests. Students' responses were analyzed to create variables for both correct and alternative conceptions of evolution. Pretest and posttest data were used to create difference scores that were compared both within and between teaching sections. Pre-to-post gains were expected in the correct (Darwinian Conception) scores, while pre-to-post losses were expected in the Alternative Conception scores. Also, students in the experimental sections were expected to perform better than those in the traditional sections. Pretest-to-posttest differences within each section showed gains in correct conceptions but few reductions in alternative conceptions. Comparisons between sections support the use of the paired problem-solving instructional strategy in conjunction with the historically rich curriculum.

A historically rich teaching intervention was developed for biological evolution with the intent of promoting a conceptual change from students' initial understanding to a more Darwinian understanding. The intervention was delivered in a small group setting to underprepared, entry-level biology students. Evaluation of the treatment, using pre-post testing, was used to document the general effectiveness of the intervention and specific changes in students' conceptions of evolution. Results indicate the use of historical materials in conjunction with a conceptual change strategy to be promising. Specific strengths and weaknesses in specific areas of biological evolution are documented. 0 1995 John Wiley & Sons, Inc. OVERVIEW PurposeThe teaching of Darwinian evolution is critical to understanding modern biology, yet it has been shown to be quite difficult (Bishop & Anderson, 1990;Brumby, 1984;Clough & Wood-Robinson, 1985; HalldCn, 1988; Smith et al., in press). This study is the evaluation of an intervention in the teaching of evolution. The intent was to conduct an ecologically valid study by examining the effects of the intervention within the time limits of a typical introductory biology course for underprepared students. The intervention was the teaching of ideas that have been important in the history of evolutionary thought in a way that meets the conditions for learning given in conceptual change theory. The intervention was done in a laboratory session associated with a biology course for nonscience majors. The evaluation was conducted as an in-depth examination of the changes in the students' knowledge that were associated with the intervention. The overall thesis of this study was that if instruction recapitulated events in the development of the Darwinian theory of evolution by natural selection, then students would replace their initial conceptions with more Darwinian conceptions.

This article presents an analysis of the projected performance of urban residential rainwater harvesting systems in the United States (U.S.). The objectives are to quantify for 23 cities in seven climatic regions (1) water supply provided from rainwater harvested at a residential parcel and (2) stormwater runoff reduction from a residential drainage catchment. Water-saving efficiency is determined using a water-balance approach applied at a daily time step for a range of rainwater cistern sizes. The results show that performance is a function of cistern size and climatic pattern. A single rain barrel (190 l [50 gal]) installed at a residential parcel is able to provide approximately 50% water-saving efficiency for the nonpotable indoor water demand scenario in cities of the East Coast, Southeast, Midwest, and Pacific Northwest, but <30% water-saving efficiency in cities of the Mountain West, Southwest, and most of California. Stormwater management benefits are quantified using the U.S. Environmental Protection Agency Storm Water Management Model. The results indicate that rainwater harvesting can reduce stormwater runoff volume up to 20% in semiarid regions, and less in regions receiving greater rainfall amounts for a long-term simulation. Overall, the results suggest that U.S. cities and individual residents can benefit from implementing rainwater harvesting as a stormwater control measure and as an alternative source of water.

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Changes in human dental plaque pH can be used to obtain estimates of the acidogenic potential of ingested foods. The presence of acid in plaque is influenced by a large number of host, microbial, and substrate factors. Several useful methods have been developed for monitoring changes in plaque pH. Plaque sampling involves repeated removal of small samples of plaque from a number of teeth at intervals after food ingestion, dispersion of the sample, and in vitro measurement of pH. Touch electrode methods utilize glass or antimony microelectrodes, which are placed onto plaque in situ where direct readings can be obtained. Telemetry methods involve placement of glass microelectrodes or ion-sensitive field effect transistors within the dentition. Plaque is allowed to accumulate, and pH changes can subsequently be transmitted with radio or wire. Each of the methods has clear advantages and limitations. The methods have been simultaneously compared in human volunteers using solutions of fermentable carbohydrate. Inter-method differences in response were observed depending upon the site of measurement. Data obtained from caries-prone surfaces via telemetry showed lower pH minima and retarded returns to resting pH levels. The technology is available for controlled comparative plaque pH studies, with the method of choice depending upon the goals of the investigation. It is essential that the results be compared to data obtained with other models designed to evaluate the cariogenic potential of foods.