Acquiring the cardinal knowledge of number words: A conceptual replication

Understanding the way in which counting represent numerosities was shown to be a long-lasting process. As shown in the Give-a-number task, acquiring the meanings of verbal number words goes through successive developmental stages in which children first learn the cardinal meanings of small number words one at a time before generalizing the cardinal principle they have induced from the first three number words to all number words within their counting range. This acquisition would take about a year, and would be completed by the age of 3 ½ years. The aim of the present study was to provide a conceptual replication of the developmental sequence described in Wynn’s study nearly 30 years ago using the Give-a-number task. A first cross-sectional study was conducted on 213 Belgian children aged between 39 and 74 months using the Give-a-number task to examine the developmental pattern and the influence of age on this acquisition. The time span of acquisition was examined in a second study in which 34 children were tested five times every months between the age of 36 to 52 months. Results showed that acquiring the cardinal meanings of number words spread out over a protracted period, far more extended than assumed by Wynn. Furthermore, children do not generalize all-at-once to large number words, the cardinal knowledge they learned on small number words. Rather, number words were found to be learned one at a time in a really progressive manner. Results were discussed with regard to their implications for the existing theories and in relation with other tasks assessing the acquisition of verbal number symbols.

Ontogeny of the Hapuka (Polyprion oxygeneios) Immune System

<p>In this study the ontogeny of the hapuka (Polyprion oxygeneios) immune system was studied during larval development. In teleost fish, the head kidney, thymus, and spleen are generally regarded as important immune organs. The head kidney was observed at 4 days post hatch (dph), the spleen at 16 dph and lastly the thymus at 20 dph and all 3 lymphoid organs were relatively well developed by 45 dph. The immune genes CSF1R, C3, MHCIIα, TCRα, TCRβ, RAG1, IgM and IgZ were examined by RT-PCR to investigate the leucocyte development. Macrophages appear to be present from hatch with both CSF1R and MHCIIα expression from 1 dph, while IgM is expressed at 9 dph. T-cells appear later in hapuka with TCRβ expression first detected at 32 dph whereas TCRα was not expressed until after 63 dph. Immunostaining using a monoclonal antibody against fish IgM detected IgM in the head kidney at 12 dph, the spleen at 32 dph, the intestinal tract at 45 dph and lastly the thymus at 50 dph. Comparison of the leucocyte populations in juveniles and adults indicated that innate cell populations are late to develop, while the adaptive cells mature earlier in hapuka than expected. Finally, the maternal transfer of immunity was examined and while lysozyme and IgM appear to be transferred, complement does not. Overall this study provides insight into the developmental sequence of immune organs and cells and will be useful in understanding the timing of immune competence in juveniles and adult hapuka.</p>

Ontogeny of the Hapuka (Polyprion oxygeneios) Immune System

<p>In this study the ontogeny of the hapuka (Polyprion oxygeneios) immune system was studied during larval development. In teleost fish, the head kidney, thymus, and spleen are generally regarded as important immune organs. The head kidney was observed at 4 days post hatch (dph), the spleen at 16 dph and lastly the thymus at 20 dph and all 3 lymphoid organs were relatively well developed by 45 dph. The immune genes CSF1R, C3, MHCIIα, TCRα, TCRβ, RAG1, IgM and IgZ were examined by RT-PCR to investigate the leucocyte development. Macrophages appear to be present from hatch with both CSF1R and MHCIIα expression from 1 dph, while IgM is expressed at 9 dph. T-cells appear later in hapuka with TCRβ expression first detected at 32 dph whereas TCRα was not expressed until after 63 dph. Immunostaining using a monoclonal antibody against fish IgM detected IgM in the head kidney at 12 dph, the spleen at 32 dph, the intestinal tract at 45 dph and lastly the thymus at 50 dph. Comparison of the leucocyte populations in juveniles and adults indicated that innate cell populations are late to develop, while the adaptive cells mature earlier in hapuka than expected. Finally, the maternal transfer of immunity was examined and while lysozyme and IgM appear to be transferred, complement does not. Overall this study provides insight into the developmental sequence of immune organs and cells and will be useful in understanding the timing of immune competence in juveniles and adult hapuka.</p>

Programmed Cell Death in Developing Brachypodium distachyon Grain

The normal developmental sequence in a grass grain entails the death of several maternal and filial tissues in a genetically regulated process termed programmed cell death (PCD). The progression and molecular aspects of PCD in developing grains have been reported for domesticated species such as barley, rice, maize and wheat. Here, we report a detailed investigation of PCD in the developing grain of the wild model species Brachypodium distachyon. We detected PCD in developing Brachypodium grains using molecular and histological approaches. We also identified in Brachypodium the orthologs of protease genes known to contribute to grain PCD and surveyed their expression. We found that, similar to cereals, PCD in the Brachypodium nucellus occurs in a centrifugal pattern following anthesis. However, compared to cereals, the rate of post-mortem clearance in the Brachypodium nucellus is slower. However, compared to wheat and barley, mesocarp PCD in Brachypodium proceeds more rapidly in lateral cells. Remarkably, Brachypodium mesocarp PCD is not coordinated with endosperm development. Phylogenetic analysis suggests that barley and wheat possess more vacuolar processing enzymes that drive nucellar PCD compared to Brachypodium and rice. Our expression analysis highlighted putative grain-specific PCD proteases in Brachypodium. Combined with existing knowledge on grain PCD, our study suggests that the rate of nucellar PCD moderates grain size and that the pattern of mesocarp PCD influences grain shape.

Designing a developmental progression to assess students’ conceptual understandings by focusing on the language demands in Science

Few would argue the value of learning progressions in providing useful structures for selecting and sequencing in a developmental manner the key components of an ‘intended curriculum’. Yet, there are pervading issues around what is meant by a developmental sequence, along with how they are used to assess what learners know, understand and can do. One key oversight in Science is recognising the role of technical and non-technical language in student conceptual development. This article reports on the construction of a hypothesised learning progression that identifies students’ progress in understanding essential concepts in the Chemical Sciences from Foundation to Year 6. It is based upon an extensive analysis of the technical and non-technical language of the Australian Curriculum: Science. The progression was constructed by focusing upon learner-appropriate language and scientific understanding with the Structure of the Observed Learning Outcome model ( Pegg, 2018 ) providing the theoretical basis for ensuring systematic and objective rigour in the resultant developmental progression.

The organization of the gravity-sensing system in zebrafish

Motor circuits develop in sequence from those governing fast movements to those governing slow. Here we examine whether upstream sensory circuits are organized by similar principles. Using serial-section electron microscopy in larval zebrafish, we generated a complete map of the gravity-sensing (utricular) system from the inner ear to the brainstem. We find that both sensory tuning and developmental sequence are organizing principles of vestibular topography. Patterned rostrocaudal innervation from hair cells to afferents creates a directional tuning map in the utricular ganglion, forming segregated pathways for rostral and caudal tilt. Furthermore, the mediolateral axis of the ganglion is linked to both developmental sequence and temporal kinetics. Early-born pathways carrying phasic information preferentially excite fast escape circuits, whereas later-born pathways carrying tonic signals excite slower postural and oculomotor circuits. These results demonstrate that vestibular circuits are organized by tuning direction and kinetics, aligning them with downstream motor circuits and behaviors.

Quantifying the vertical diversification development stage of old-growth Douglas-fir to derive stage-specific targets for restoration silviculture

Structural variability in natural Douglas-fir (Pseudotsuga menziesii (Mirbel) Franco) forests hinders restoration targets for the full old-growth developmental sequence. To guide stage-specific restoration, we present a new approach toward developing a simple index of the vertical diversification (VD) stage. VD-associated sub-stand structures were objectively identified by quantifying the size structures of live trees across a developmental sequence of 10 pristine stands in the Oregon Cascades, USA. Floating neighborhoods were used to delineate natural tree neighborhoods based on triangulated irregular networks in five concentric rings of ever-greater spatial extent (averaging 60–2060 m2). Diameter distributions summarized the most frequently encountered tree size structures among neighborhoods, with increasing deviation from the neutral multi-variate core. Of 18 observed diameter distribution types (DDTs), the core DDT characterized all-sized tree neighborhoods reflective of vertical diversification, which was most abundant in early old-growth (VD) stands and least abundant at the extremes of the sequence. VD declined in older stands, whose more distinct DDTs had peaks in larger trees and multiple size classes, likely reflecting horizontal diversification (HD). This new approach illustrates that structural restoration of VD stands could be facilitated by the single-tree selection method, while that of HD stands may be promoted with both single-tree and group selection as well as targeted release.

Development of the foregut in Katharina tunicata (Mollusca; Polyplacophora)

As a highly diverse phyla, Mollusca is both intriguing to study and difficult to define. No single common feature distinguishes the phyla, but the most common and recognizable is the radula. Throughout Molluscan history, there have been many developments to the radular structure. Evolutionary development of unique radular structures may have been made possible by developmental modularity. This histological study examines the development of polyplacophoran internal gut development. Here, I describe the developmental sequence of chiton feeding structures for the first time. Feeding structures are present by 10 days post hatch. Future research should examine larval stages prior to this in order to determine whether developmental modularity exists in polyplacophorans.