Human organisms begin to exist at fertilization

Eugene Mills has recently argued that human organisms cannot begin to exist at fertilization because the evidence suggests that egg cells persist through fertilization and simply turn into zygotes. He offers two main arguments for this conclusion: that ‘fertilized egg’ commits no conceptual fallacy, and that on the face of it, it looks as though egg cells survive fertilization when the process is watched through a microscope. We refute these arguments and offer several reasons of our own to think that egg cells do not survive fertilization, appealing to various forms of essentialism regarding persons, fission cases, and a detailed discussion of the biological facts relevant to fertilization and genetics. We conclude that it is plausible, therefore, that human organisms begin to exist at fertilization – or, at the very least, that there are grounds for thinking that they existed as zygotes which do not apply to the prior egg cells. While this does not entail that human persons begin to exist at this point, it nevertheless has considerable significance for this latter question.     

Advanced-level Biology—A Possible Approach

Teachers' conscious priorities in selecting topics for teaching rarely include the ‘biology/social science interfaces’; neither are many usually aware of the existence and implications of ‘hidden ideologies’ in the curriculum. This paper gives several examples of such interfaces, and stresses the point that only by redirecting the education of teachers can their awareness and priorities be suitably altered.     

Development of cranial muscles in the actinopterygian fish Senegal bichir,Polypterus senegalus Cuvier, 1829

Polypterus senegalus Cuvier, 1829 is one of the most basal living actinopterygian fish and a member of the Actinopterygii. We analyzed the spatial and temporal pattern of cranial muscle development of P. senegalus using whole‐mount immunostaining and serial sectioning. We described the detailed structure of the external gill muscles which divided into dorsal and ventral parts after yolk exhaustion. The pattern of the division is similar to that of urodeles. We suggest that, the external gill muscles of P. senegalus are involved in spreading and folding of the external gill stem and the branches. The fibers of the external gill muscles appear postero‐lateral to the auditory capsule. In addition, the facial nerve passes through the external gills. Therefore, the external gill muscles are probably derived from the m. constrictor hyoideus dorsalis. In contrast to previous studies, we described the mm. interhyoideus and hyohyoideus fibers as independent components in the yolk‐sac larvae. The m. hyohyoideus fibers appear lateral to the edge of the ventral portion of the external gill muscles, which are probably derived from the m. constrictor hyoideus dorsalis. These findings suggest that the m. hyohyoidues is derived from the m. constrictor hyoideus dorsalis in P. senegalus . In other actinopterygians, the m. hyohyoideus is derived from the m. constrictor hyoideus ventralis; therefore, the homology of the m. hyohyoidues of P. senegalus and other actinopterygians remains unclear. J. Morphol. 278:450–463, 2017. © 2017 Wiley Periodicals, Inc.     

The common patterns of nature

We typically observe large‐scale outcomes that arise from the interactions of many hidden, small‐scale processes. Examples include age of disease onset, rates of amino acid substitutions and composition of ecological communities. The macroscopic patterns in each problem often vary around a characteristic shape that can be generated by neutral processes. A neutral generative model assumes that each microscopic process follows unbiased or random stochastic fluctuations: random connections of network nodes; amino acid substitutions with no effect on fitness; species that arise or disappear from communities randomly. These neutral generative models often match common patterns of nature. In this paper, I present the theoretical background by which we can understand why these neutral generative models are so successful. I show where the classic patterns come from, such as the Poisson pattern, the normal or Gaussian pattern and many others. Each classic pattern was often discovered by a simple neutral generative model. The neutral patterns share a special characteristic: they describe the patterns of nature that follow from simple constraints on information. For example, any aggregation of processes that preserves information only about the mean and variance attracts to the Gaussian pattern; any aggregation that preserves information only about the mean attracts to the exponential pattern; any aggregation that preserves information only about the geometric mean attracts to the power law pattern. I present a simple and consistent informational framework of the common patterns of nature based on the method of maximum entropy. This framework shows that each neutral generative model is a special case that helps to discover a particular set of informational constraints; those informational constraints define a much wider domain of non‐neutral generative processes that attract to the same neutral pattern.     

An adjuvant strategy enabled by modulation of the physical properties of microbial ligands expands antigen immunogenicity

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Uncertainty in the detection of disturbance spatial patterns in temperate forests

The use of individual-based models in the study of the spatial patterns of disturbances has opened new horizons in forest ecosystem research. However, no studies so far have addressed (i) the uncertainty in geostatistical modelling of the spatial relationships in dendrochronological data, (ii) the number of increment cores necessary to study disturbance spatial patterns, and (iii) the choice of an appropriate geostatistical model in relation to disturbance regime. In addressing these issues, we hope to contribute to advances in research methodology as well as to improve interpretations and generalizations from case studies.We used data from the beech-dominated Žofínský Prales forest reserve (Czech Republic), where we cored 3020 trees on 74 ha. Block bootstrap and geostatistics were applied to the data, which covered five decades with highly different disturbance histories. This allowed us to assess the general behavior of various mathematical models. Uncertainty in the spatial patterns and stability of the models was measured as the length of the 95% confidence interval (CI) of model parameters.According to Akaike Information Criterion (AIC), the spherical model fitted best at the range of ca. 20 m, while the exponential model was best at the range of ca. 60 m. However, the best fitting models were not always the most stable. The stability of models grew significantly with sample size. At <500 cores the spherical model was the most stable, while the Gaussian model was very unstable at <300 cores. The pure nugget model produced the most precise nugget estimate. The choice of model should thus be based on the expected spatial relations of the forest ecosystem under study. Sill was the most stable parameter, with an error of ±6–20% for ≥1110 core series. By contrast, practical range was the most sensitive, with an error of at least ±59%. The estimation of the spatial pattern of severe disturbances was more precise than that of fine-scale disturbances.The results suggest that with a sample size of 1000–1400 cores and a properly chosen model, one reaches a certain precision in estimation that does not increase significantly with growing sample size. It appears that in temperate old-growth forests controlled by fine-scale disturbances, it is necessary to have at least 500 cores to estimate sill, nugget and relative nugget, while to estimate practical range at least 1000 cores are needed. When choosing the best model, the stability of the model should be considered together with the value of AIC. Our results indicate the general limits of disturbance spatial pattern studies using dendrochronological and geostatistical methods, which can be only partially overcome by sample size or sampling design.     

Seasonal pattern of accumulation and effects of low temperatures on storage compounds in Trifolium repens

The seasonal pattern of concentrations of nitrogen, starch and vegetative storage protein (VSP) in stolons of Trifolium repens L. grown in the field were studied. Two different genotypes, cv. Aran and cv. Rivendel, differing in their morphology (stolon thickness and branching rate) but with similar growth rates, were used. Maximum concentrations of starch were found in summer whereas hydrolysis of starch took place throughout winter, suggesting that C storage is more important for winter survival than for promotion of early spring growth. On the other hand, VSP and nitrogen accumulated in autumn and early winter and then decreased when growth was resumed during early spring. For both cultivars, an inverse relationship was found between VSP concentration in stolons and mean air temperature, suggesting that VSP accumulation may be triggered by low temperature. Further experiments with plants grown under different regimes of temperature and daylength, suggested that VSP synthesis is stimulated by low root temperatures, with a slight synergistic effect of short daylength.
The effects of root temperature on growth, N₂ fixation, NH₄⁺ uptake and N allocation within Trifolium repens L., were studied under controlled conditions. The shoot growth rate was greatly reduced when root temperatures were lowered from 12 to 6°C, while the rate of stolon growth was less affected. Low root temperatures inhibited N2 fixation more than it did NH₄⁺ uptake, but the relative allocation of N to stolons was increased. Lowering root temperature also increased the accumulation of VSP in stolons. These results are discussed in terms of the mechanism associated with low temperature stimulation of VSP accumulation and its coupling with changes in the source/sink relations for allocation of N, between growth and storage.     

A range wide geographic pattern of genetic diversity and population structure of Hexinia polydichotoma (Asteraceae) in Tarim Basin and adjacent areas

In order to investigate the genetic diversity and influence of climate oscillations on evolutionary processes of organisms in northwest China, we selected Hexinia polydichotoma, a species endemic to China, and examined the geographic pattern of genetic variation in its entire cover range, Tarim Basin and adjacent areas. In the study, 22 chloroplast (cp) haplotypes were identified based on two cpDNA sequences (trnH–psbA and ycf6–psbM), and five ITS sequence variations were found. Shown in the cp haplotype network, the two common cp haplotypes mainly distributed along the northern and southern rims of the basin respectively and intersected in the center of the basin, whereas in the ITS network, ITS genotype 1 was widespread across the whole distribution area, and rare genotypes were concentrated in the western rim of the basin. Genetic variation primarily occurred among populations and SAMOVA groups. Fragmented desert habitat may have caused gene flow barrier among populations or groups far from each other, leading to significant genetic differentiation at these levels. It appears that expansion and contraction cycles of river systems and oases during the middle Pleistocene was the source of the observed fragmentation. Geographic range expansion in H. polydichotoma was supported by the significant value for Tajima's D, Fu's F_S, and by a unimodal mismatch distribution. It was possible that the enlargement of the Taklimakan Desert during the middle Pleistocene may have provided appropriate conditions for the range dispersal. We identified western rim of the basin as the center of genetic diversity of H. polydichotoma based on the present dataset.