Social amoebae mating types do not invest unequally in sexual offspring

Unequal investment by different sexes in their progeny is common and includes differential investment in the zygote and differential care of the young. The social amoeba Dictyostelium discoideum has a sexual stage in which isogamous cells of any two of the three mating types fuse to form a zygote which then attracts hundreds of other cells to the macrocyst. The latter cells are cannibalized and so make no genetic contribution to reproduction. Previous literature suggests that this sacrifice may be induced in cells of one mating type by cells of another, resulting in a higher than expected production of macrocysts when the inducing type is rare and giving a reproductive advantage to this social cheat. We tested this hypothesis in eight trios of field-collected clones of each of the three D. discoideum mating types by measuring macrocyst production at different pairwise frequencies. We found evidence that supported differential contribution in only two of the 24 clone pairs, so this pattern is rare and clone-specific. In general, we did not reject the hypothesis that the mating types contribute cells relative to their proportion in the population. We also found a significant quadratic relationship between partner frequency and macrocyst production, suggesting that when one clone is rare, macrocyst production is limited by partner availability. We were also unable to replicate previous findings that macrocyst production could be induced in the absence of a compatible mating partner. Overall, mating type-specific differential investment during sex is unlikely in microbial eukaryotes like D. discoideum

The Effect of a Paired Lab on Course Completion and Grades in Nonmajors Introductory Biology

This paper explores the effect of a paired lab course on students’ course outcomes in nonmajors introductory biology at the University of Alaska Anchorage. We compare course completion and final grades for 10,793 students (3736 who simultaneously enrolled in the lab and 7057 who did not). Unconditionally, students who self-select into the lab are more likely to complete the course and to earn a higher grade than students who do not. However, when we condition on observable course, academic, and demographic characteristics, we find much of this difference in student performance outcomes is attributable to selection bias, rather than an effect of the lab itself. The data and discussion challenge the misconception that labs serve as recitations for lecture content, noting that the learning objectives of science labs should be more clearly articulated and assessed independent of lecture course outcomes. This paper explores the effect of a paired lab course on students’ course outcomes in introductory biology for nonmajors at the University of Alaska Anchorage (UAA), a large, open-enrollment, 4-year university. We compare outcomes for 10,793 students, 3736 who simultaneously enrolled in the lab and 7057 who did not, and analyze the degree to which they select into the lab on observable characteristics to explore the following research questions: 1. Are students who take a paired lab more likely to complete the lecture component (i.e., receive a final grade as opposed to withdrawing or receiving an Incomplete)? 2. Are students who take a paired lab more likely to receive a higher grade in the lecture component? 3. Does the laboratory experience differently affect course outcomes for students in specific demographic subgroups (e.g., gender, race, high school urbanicity, age, prior academic performance, and socioeconomic status)

Does resource availability help determine the evolutionary route to multicellularity?

Genetic heterogeneity and homogeneity are associated with distinct sets of adaptive advantages and bottlenecks, both in developmental biology and population genetics. Whereas populations of individuals are usually genetically heterogeneous, most multicellular metazoans are genetically homogeneous. Observing that resource scarcity fuels genetic heterogeneity in populations, we propose that monoclonal development is compatible with the resource-rich and stable internal environments that complex multicellular bodies offer. In turn, polyclonal development persists in tumors and in certain metazoans, both exhibiting a closer dependence on external resources. This eco-evo-devo approach also suggests that multicellularity may originally have emerged through polyclonal development in early metazoans, because of their reduced shielding from environmental fluctuations

Hemoglobin Level in Elite Speed Skaters from 2000 up to 2005, and its Relationship with Competitive Results

We studied the mean hemoglobin (Hb) concentration in elite male and female long track junior and senior speed skaters from 2000 to 2005. In addition, the number of abnormal hematological findings observed over this period of time was investigated. We also studied whether there were differences in Hb concentration between top ranked and lower ranked skaters, and whether a relationship between Hb concentration and competitive results could be observed. The present study shows that the mean Hb level in male and female junior and senior long track speed skaters remained fairly stable and did not change from 2000 through 2005. The number and percentage of abnormal hematological findings were found to vary between 0 and 2 %, and failed to show a clear pattern or trend over the years. There was no difference in mean Hb levels between top ranked and lower ranked skaters, and no meaningful relationship between Hb concentration and ranking could be found

Blood testing in sport: hematological profiling.

Hemoglobin concentration and percent reticulocytes (%retics) were analyzed in blood samples taken pre-competition, post-competition, and during out of competition testing in elite speed skaters. Percent reticulocytes during screening was not different from the values obtained post-race, and no significant gender difference was found. Mean hemoglobin concentration both in males and females was slightly higher at 1 425 m altitude compared to 2.4% in 52 skaters at least two consecutive samples yielded a percent reticulocytes above 2.4%. In 50 individuals with generally normal values but at least in two consecutive samples values above 2.4% the pattern required additional testing. In conclusion, percent reticulocytes are a robust hematological parameter, including acute exercise