New Approaches to Understanding the Mechanics of Burgess Shale-type Deposits: From the Micron Scale to the Global Picture

Cambrian Burgess Shale-type (BST) deposits are among the most significant deposits for understanding the “Cambrian explosion” because they contain the fossilized tissues of nonmineralized organisms and provide a substantially different window on the radiation of the Metazoa than is afforded by the more “typical” fossil record of skeletal parts of biomineralized organisms. Despite nearly a century of research, BST deposits remain poorly investigated as sedimentologic entities largely because they comprise fine-grained mudrocks. Here,we describe a new, integrative approach to understanding a single BST deposit, the middle Cambrian Wheeler Formation of Utah, which reveals a dynamic interplay of paleoenvironmental, paleoecologic, and sedimentologic/diagentic factors within a superficially homogeneous lithofacies.This millimeter-scale microstratigraphic and paleontologic approach is augmented by both outcrop and microscopic study.These types of data are applicable to issues of quite different scales, including micron-scale diagenetic processes involved in fossil preservation, organism-environment interactions and paleoecology of the early Metazoa, and regional and global controls on the distribution of BST deposits

Population Dynamics of \u3ci\u3eMicrotus Ochrogaster\u3c/i\u3e in Eastern Kansas

Four eastern Kansas populations of the prairie vole, Microtus ochrogaster were live trapped from 1970—73 to gain insight into the population regulation of this species. All four populations exhibited a 2—yr cycle in numbers with peak densities generally occurring in June 1972. Peak densities were followed by a decline in numbers, a recovery, and a population crash in spring 1973. Reproductive parameters changed dramatically as density rose and fell. The summer breeding season in the crash year of 1973 was shortened by at least 3 mo. A reduction in breeding activity occurred during the summer of every year of the study. The highest amount of reproduction occurred during the spring and fall. More voles were breeding during the winter before the peak year (1971—72) than during either the preceding or succeeding winter. There was no deviation from a sex ratio of 1 in the populations. Mortality rates had a strong impact on changes in numbers. Survival rates of juveniles and subadults in the population were significantly lower than adults in the summer breeding season. Adults survived better during winter than during summer. Survival of ♂ ♂ and ♀ was correlated and was relatively low during episodes of decreasing density. The survival of voles between weaning and trappable size was high during periods of increasing density and low during periods of declining density. A multiple regression analysis was performed to determine the relative usefulness of four demographic variables in predicting mean rate of population increase. The analysis indicated that early juvenile and ♀ survival are the best predictors of population growth. Growth of voles in the populations was assessed from body weight distributions and instantaneous growth rate per body weight. There was no shift in body weight toward heavier animals in peak populations and instantaneous growth rates were erratic. Finally, inconsistencies in these results compared with other microtine studies, such as the short peak phase, lack of a well—defined breeding season, a summer breeding depression, and the absence of a shift towards heavier animals in the peak phase, are discussed in relation to a single or multifactor hypothesis for explaining population cycles

The Reproductive Cycle of \u3ci\u3eMicrotus ochrogaster\u3c/i\u3e in Eastern Kansas

About 800 Microtus ochrogaster were live—trapped at biweekly intervals from May 1971 through March 1973 in 3 grassland study areas in eastern Kansas, USA. Details of reproduction were determined by autopsy. Population density increased through the first winter, reached a peak in April 1972, then declined sharply during that summer and beyond. Body length, but not body mass, tended to be positively related to density. Both sexes matured at about the same weight; development was somewhat prolonged during the winter months, especially in the winter preceding the population peak. Pregnancy rates were high, approaching maximal iteroparity, throughout the study, with intervals of nonbreeding in both Julys, and in August and December of the population decline. Embryo counts increased significantly during the months of peak density but did not diminish in the period of the population decline. There was no association between either maternal weight or parity and number of embryos. Corpora counts were not higher in heavy or multiparious ♀ ♀, nor did the level of prenatal mortality increase during the period of greatest density. Except for a few individuals taken in July and August 1971, ♂ ♂ with a mass 30 g or more were judged to be fertile, as were a majority of the 20 to 29—g ♂ ♂. Body weight and testes weight were significantly correlated in fertile ♂ ♂ but not in nonfertile ♂ ♂. These reproductive findings were applied to a model of population regulation of microtine cycles. The pattern of reproduction of Kansas and Indiana prairie voles was compared. Three concordant lines of evidence seem to indicate that Kansas and possibly other geographical populations of prairie voles have adjusted the breeding schedule to accommodate both hot and dry summers and cold, snowy winters. Pregnancy rate, litter size, and adjusted testes weight all show a significant increase in March–April and September–October and a decrease in midsummer and midwinter. Thus the pattern of reproduction of Kansas prairie voles may represent a composite of the patterns shown by the dry—adapted species, such as Microtus californicus, and the cold—adapted microtines, such as Microtus pennsylvanicus. Based on the observations of this study, Kansas prairie voles seem to have adjusted to both harsh seasons by breeding more or less continuously, with the midsummer depression possibly reflecting the Great Plains origin of the species, and the winter depression being a facultative response to weather, density, or quality of habitat

Formerly Incarcerated Students Returning to School

Formerly incarcerated Grade 10\u2712 students in an urban high school in the Southern United States were dropping out at an elevated rate from August 2010 through May 2017. The purpose of this qualitative descriptive study was to gain an understanding of teacher, parent, and academic advisor perceptions of the challenges experienced by Grade 10\u2712 students who had been incarcerated and then returned to a traditional school environment and support services and resources needed to assist with these challenges. Hirschi\u27s social control theory guided this study, which describes 4 elements missing from individuals participating in criminal activity: attachment, commitment, involvement, and belief. The 3 research questions addressed (a) parent, teacher, and academic advisor perceptions of the challenges faced by former incarcerated students returning to school, (b) support services and resources needed for those students, and (c) suggestions for administrators to better help those students. Data were collected from 6 teachers, 6 parents, and 6 Academic Advisors, through semistructured interviews and analyzed using Hatch\u27s 9-step typology. The findings indicated that students who had been incarcerated struggled due to issues such as (a) poor academics, (b) peer influence, (c) lack of interest in school, (d) drug and gang involvement, (e) poor communication with the school, (f) mental illness, and (g) behavior problems. The resulting project led to the development of a policy recommendation with supporting white paper focusing on specific interventions to resolve the challenges faced by incarcerated students transitioning back to a typical school environment experience. The study promotes positive social change through increased graduation rates for formerly incarcerated students

Additional Comments on Reproductive Strategies and Population Fluctuations in Microtine Rodents

Recently, Schaffer and Tamarin (1973) proposed a model relating changes in reproductive effort (RE) to fluctuating densities in microtine rodents (lemmings and voles). They assumed (and presented data supporting this assumption) that the major effect of increased crowding would be a reduction in survival among prereproductives, thereby lowering the effective fecundity (Schaffer and Rosenzweig 1977) of their parents. As a consequence, Schaffer and Tamarin argued that the optimal reproductive expenditure, E(N), should decline with increasing population size, N. They also deduced the shape of the zero-growth isocline, N*(E), for differing levels of RE and plotted both E(N) and N*(E) on a graph whose axes are reproductive expenditure and population density (Fig1 a)

Проблеми впровадження методів профорієнтаційної роботи в середній школі

(uk) В статті розглядаються актуальні проблеми проведення профорієнтаційної роботи в середній школі, характеризуються основні методи цієї роботи.(en) In the article examined issues of the day of leadthrough professionally of orientation work at middle school, the basic methods of this work are characterized