Explicações teleológicas no ensino de evolução

O presente estudo tem como finalidade investigar o pensamento teleológico e suas implicações para o ensino e a formação de professores de Biologia. Particularmente, visa a compreender como os professores utilizam os argumentos teleológicos na elaboração das explicações sobre temáticas de evolução no ensino de Biologia. O trabalho empírico focaliza as soluções apresentadas por docentes às diversas situações em que o pensamento teleológico assume em aula, nas quais predominam uma visão linear e progressista sobre evolução. Tomando como referência a análise realizada, argumenta-se que a complexidade do pensamento teleológico não se restringe ao ensino Biologia e, portanto, os usos dados didáticos devem ser analisados em relação às finalidades educativas e não unicamente aos critérios científicos. Apontamos para seu uso consciente e em situações específicas

The effect of long-term application of P fertilizer on soil grown forage plants

Non-Peer ReviewedPhosphorus (P) fertilization does not always increase crop yields but the repeated use of P may modify the biological properties of soils. The objective of the present study, therefore, was to investigate the effect of long term applications of P fertilizer on soil biological properties. We used an experimental site located in Swift Current in which different amounts of P (0, 20 and 40 kg P2O5 ha-1) were applied annually for the past 8 years on alfalfa and alfalfa-Russian wild rye hay crops. Our hypothesis was that repeated application of P influences soil microbial biomass and various soil enzymes. Microbial biomass C in the 0-7.5 cm soil layer was determined by fumigation-extraction at each of three harvest dates, and dehydrogenase, acid phosphatase and urease activities were assayed. Application of P to soil increased soil available P, dissolved organic C and available NO3-N, but did not significantly affect crop yields or soil microbial biomass C. Arbuscular mycorrhizal colonization of crop roots, and dehydrogenase and urease activities were decreased, suggesting that P reduced soil microbial activity. Acid phosphatase activity remained unchanged with P fertilization, suggesting that P availability was not limiting in these systems. While 8 years of application of P had little effect on hay yields, it generally reduced the activity of the soil microbial biomass

Effect of source, placement, and time of N application on winter wheat grown on stubble in the Brown and Black Soil Zones

Non-Peer Reviewe

Influence of pulse crops on arbuscular mycorrhizal fungi in a durum-based cropping system

Non-Peer ReviewedPulses are an important component in crop rotations in southern Saskatchewan. Besides their capability to fix nitrogen, pulse crops establish a symbiotic relationship with arbuscular mycorrhizal fungi, which have been shown to increase nutrient and water uptake through hyphal extensions in the soil. This 2 year study is designed to evaluate the impact of pulses in crop rotations on the biodiversity of AMF communities and their dynamics. Plant N and P uptake and the available soil N and P pools under a durum crop are also measured to assess if there is any correlation with AMF communities. The sampling and analysis is completed on the durum phase of the rotation with preceding crops of pea, lentil, chickpea, canola and durum. The final results will be explained by: (1) the size, nature, and physiological state of the soil microbial community and (2) the nature of the preceding crop residues. Preliminary results from the 2004 season indicate that higher plant P uptake is related to AMF colonization, while no significant change was detected in the soil N and P pools

Seasonal variation in the soil microbial community in wheat-growing soil and influence of C, N, and P inputs

Non-Peer ReviewedIt has long been know that N and P fertilization increases plant growth and yield, but the impact of fertilization on soil microorganisms has rarely been considered. Long-term plots (36-year old) under fallow-wheat-wheat (F-W-W) rotations with no P or no N fertilization, or normally fertilized, and plots receiving low C inputs due to frequent fallow (F-W rotation) were used to define the impact of C, N and P on the seasonal variation of the soil microbial communities in the fallow-after-wheat or the wheat-after-fallow phases of the rotations. The soil was sampled on June 8, July 4, August 5 and September 16, in 2003. There was no significant (P≤ 0.05) time by treatment interactions. Populations of bacteria, arbuscular mycorrhizal (AM) fungi and saprophytic fungi, as estimated by phospholipids fatty acid (PLFA) indicators, were strongly reduced on July 4th, a date corresponding to rapid plant growth. Sporulation of fungal saprobes was enhanced at that date, as indicated by the neutral lipid fatty acid (NLFA) to PLFA fraction ratio of the fatty acid C18:2. It appears that a competition for resources exists between soil microorganisms and wheat, at least in July at the time of active crop growth. While P availability had little effect on soil microorganisms, absence of N fertilization increased sporulation in AM and saprophytic fungi. In spite of the biotrophic1 nature of AM fungi, C input in the form of infrequent fallow or presence of living wheat plant favoured the partitioning of fatty acids into reserve lipid i.e., NLFA

Microbial community structure under various wheat-based cropping systems

Non-Peer ReviewedThe effects of cropping systems on soil biological quality are slow to develop. We sampled the soil of a 36-year old long-term experiment established on an Orthic Brown Chernozem, at Swift Current SK, in the fall of 2003, to define the long-term impact of 10 cropping systems on soil biological quality. Numerous variables related to soil function - soil pH, organic C (SOC), moisture, enzymatic activities, available N, P, and S - and soil community structure - phospholipid fatty acids (PLFA) indicators of fungal saprobes, arbuscular mycorrhizal fungi and bacterial groups - were used to describe soil quality. Soils under different cropping systems had become distinct, as revealed by discriminant analyses. Variations in SOC, and pH were most influential in discriminating the soils. SOC varied from 2.38% under continuous wheat to 1.81% under a fallow-wheat rotation. pH went from 6.55 under fallow-wheat-wheat receiving no P-fertilizer, to 4.89, under chemical fallow – fall rye – wheat. Absence of fallow under normal fertilization increased SOC and decreased soil pH. Variations in SOC and pH were concurrent with variations in microbial community structure. Enhanced AM fungi abundance under low soil P, could compensate for the large soil P depletion created by 36 years without P fertilizer, in a fallow-wheat-wheat rotation, and P-fertilized and non-P-fertilized plots produced similar yields. The season of 2003 was dryer than normal and it remains to be seen if AM fungi can compensate for low soil available P when soil moisture is abundant

External Validation of a Dynamic Prediction Model for Upper Limb Function After Stroke

Objective: To externally validate the dynamic prediction model for prediction of upper limb (UL) function 6 months after stroke. The dynamic prediction model has been developed and cross-validated on data from 4 Dutch studies. Design: Data from a prospective Danish cohort study were used to assess prediction accuracy. Setting: A Danish neurorehabilitation hospital. Participants: In this external validation study, follow-up data for 80 patients in the subacute phase after stroke (N=80), mean age 64 (SD11), 43% women, could be obtained. They were assessed at 2 weeks, 3 months, and 6 months after stroke with the Action Research Arm Test (ARAT), Fugl-Meyer Motor Assessment upper limb (FMA), and Shoulder Abduction (SA) Finger Extension (FE), (SAFE) test. Intervention: Not applicable. Main Outcome Measures: Prediction accuracy at 6 months was examined for 3 categories of ARAT (0-57 points): mild (48-57), moderate (23-47), and severe (0-22). Two individual predictions of ARAT scores at ±6 months post-stroke were computed based on, respectively, baseline (2 weeks) and 3 months ARAT, FE, SA values. The absolute individual differences between observed and predicted ARAT scores were summarized. Results: The prediction model performed best for patients with relatively good UL motor function, with an absolute error median (IQR) of 3 (2-9), and worst for patients with severe UL impairment, with a median (IQR) of 30 (3-39) at baseline. In general, prediction accuracy substantially improved when data obtained 3 months after stroke was included compared with baseline at 2 weeks after stroke. Conclusion: We found limited clinical usability due to the lack of prediction accuracy 2 weeks after stroke and for patients with severe UL impairments. The dynamic prediction model could probably be refined with data from biomarkers.</p

Productivity and economic performance of spring wheat production using conventional tillage practices in southwestern Saskatchewan – revisited

Non-Peer Reviewe

Effect of cropping frequency on grain yields, N balance, and economic returns for properly fertilized spring wheat in southwestern Saskatchewan

Non-Peer Reviewe