Argument-Driven Engineering in Middle School Science: An Exploratory Study of Changes in Engineering Identity Over an Academic Year

The goal of this study was to examine how the use of a new instructional model is related to changes in middle school students’ engineering identity. The intent of this instructional model, which is called argument-driven engineering (ADE), is to give students opportunities to design and critique solutions to meaningful problems using the core ideas and practices of science and engineering. The model also reflects current recommendations found in the literature for supporting the development or maintenance of engineering identity. This study took place in the context of an eighth-grade science classroom in order to explore how middle school students’ engineering identities change over time as they become more familiar with engineering core ideas and practices. One hundred students participated in this study. These students completed three design tasks during the school year that were created using the ADE instructional model. These students also completed a survey that was designed to measure two important aspects of an engineering identity (recognition and interest) at three different time points. The results of a hierarchical linear modeling analysis suggest that students’ ideas about how they view themselves and others view them in terms of engineering did not change over time and their reported interest decreased from one survey to the next. The difficulty of the design tasks and the ways teachers enacted the instructional model are proposed as potential explanations for this counterintuitive finding

Abscisic acid induced a negative geotropic response in dark-incubated Chlamydomonas reinhardtii

© 2019, The Author(s). The phytohormone abscisic acid (ABA) plays a role in stresses that alter plant water status and may also regulate root gravitropism and hydrotropism. ABA also exists in the aquatic algal progenitors of land plants, but other than its involvement in stress responses, its physiological role in these microorganisms remains elusive. We show that exogenous ABA significantly altered the HCO3− uptake of Chamydomonas reinhardtii in a light-intensity-dependent manner. In high light ABA enhanced HCO3− uptake, while under low light uptake was diminished. In the dark, ABA induced a negative geotropic movement of the algae to an extent dependent on the time of sampling during the light/dark cycle. The algae also showed a differential, light-dependent directional taxis response to a fixed ABA source, moving horizontally towards the source in the light and away in the dark. We conclude that light and ABA signal competitively in order for algae to position themselves in the water column to minimise photo-oxidative stress and optimise photosynthetic efficiency. We suggest that the development of this response mechanism in motile algae may have been an important step in the evolution of terrestrial plants and that its retention therein strongly implicates ABA in the regulation of their relevant tropisms