We advance this long tradition of surveying teachers with reports from the first nationally representative survey of teachers concerning the teaching of evolution. The survey permits a statistically valid and current portrait of US science teachers that complements US and international surveys of the general public on evolution and scientific literacy [2,24] and on evolution in the classroom [3,25]. Between March 5 and May 1, 2007, 939 teachers participated in the study, either by mail or by completing an identical questionnaire online. Our overall response rate of 48% yielded a sample that may be generalized to the population of all public school teachers who taught a high school-level biology course in the 2006-2007 academic year, with all percentage estimates reported in this essay’s tables and figures having a margin of error of no more than 3.2% at the 95% confidence level. Detailed discussion of the methods of the survey and assessments of non-response can be found in Text S1. Our results confirm wide variance in classroom instruction and indicate a clear need to focus not only on state and federal policy decisions, but on the everyday instruction in American classrooms.
The existence of circadian clocks, which allow organisms to predict daily changes in their environments, have been recognized for centuries, yet only recently has the molecular machinery responsible for their generation been uncovered. The current model in animals posits that interlocked feedback loops of transcription-translation produce these 24-hour rhythms. In fruit flies, the transcription loop contains a key activator complex, composed of the transcription factors Clock and Cycle. This CLK-CYC complex stimulates the synthesis of repressor proteins like Period and Timeless, which repress the activator complex. The synthesis-repression cycle takes precisely 24 hours under environmental conditions that influence the circadian period. An almost identical process relies on the ortholog proteins CLK-BMAL in mammals. Recent findings have challenged the transcription-translation feedback model and suggest that circadian transcription is an output process and that the post-translational modification of clock proteins is the real central pacemaker mechanism. In the present study, we have manipulated the levels and strength of the CLK-CYC complex. The results demonstrate that its activity is vital for proper period determination and thus indicate that the transcriptional feedback loop is part of the core circadian mechanism.
In the last decade or so, we have become familiar with the discovery of new classes of nuclear-encoded regulators (see Glossary) as fundamental controllers of gene expression. Each new discovery has again highlighted the incomplete nature of our understanding of the genome and its regulation. First, small interfering RNAs (siRNAs) demonstrated that RNA molecules are not merely components of the cellular machinery (such as tRNAs and rRNAs) or gene-expression intermediates (mRNAs), but can function as potent trans-acting regulators of specific genes. MicroRNAs (miRNAs) continued this theme and now attract much attention among basic scientists and clinicians alike, both as potential regulators of most human genes and as potential diagnostic tools. In this issue of PLoS Medicine, a research article by Shigetada Teshima-Kondo and colleagues supports the suggestion that another class of regulatory RNAs exists . Furthermore, this class could be the largest to date, since potential members are contained within every mRNA.
Population ecology–the science of what makes animal and plant populations change, persist, or go extinct–is the most theoretical and mathematical of all ecological disciplines, yet it yields a huge number of practical benefits. When conservation agencies wish to protect a threatened species, but are up against a tight budget and real-world logistical constraints, they use population models to tell them how large an area to reserve and how it should be connected to other habitats, so as to minimise the species’ risk of extinction. In short, population ecology tells us how to get the best “bang for our buck” . Similarly, fishery managers face the perennial issue of determining how heavily they can exploit a fluctuating fish stock without over-harvesting and causing a crash (or extinction). Again, population models, of various complexities, provide guidance in setting fishing quotas and no-take areas .