A model for unequal ventilation of the lungs assuming a common dead space and two separate dead spaces

This is a model for the time-variation of helium concentrations in lung wash-out curves. The helium (or other inert gas) is in a spirometer, which is connected by a common dead space to two separate dead spaces, each of which leads into a chamber. The chambers expand and contract, thus taking in some helium at each “breath.” Equations for the changes in helium concentration in each part of the system are set up; in this way difference equations are derived for the amount of helium in the spirometer after each breath, in and out, and complete solutions when the initial concentration is zero in all parts of the system except the spirometer. A simple solution when the chambers do not essentially differ (“equal ventilation”) is compared with the general case. The concept of “unequal lung ventilation” is discussed critically in relation to the model; some physiological interpretations are also mentioned. Numerical examples are given to show the effect of changes in various constants, in particular tidal volumes, end volumes, and the common dead space.     

Chain processes and their biophysical applications: Part I. General theory

A mathematical theory applicable to the biological effects of radiations as chain processes is developed. The theory may be interpreted substantially as a “hit theory” involving the concepts of “sensitive volume” or “target area”. The variability of the sensitivity of the organism to the radiation and its capacity of recovery between single hits is taken into account. It is shown that in a continuous irradiation of a biological aggregate in which the effect of each single hit cannot be observed, recovery and variation of sensitivity are formally equivalent to each other so that a discrimination between these two phenomena is possible only by discontinuous irradiation or by using different radiation intensities. Methods for the calculation of the “number of hits” and for the determination of the kinetics of the processes from “survival curves” or similar experimental data are given. The relation between the recovery and the Bunsen-Roscoe law is discussed. The case in which the injury of the organism is dependent on the destruction of more than one “sensitive volume” is also considered.     

The advantages and disadvantages of being introduced

Introduced species, those dispersed outside their natural ranges by humans, now cause almost all biological invasions, i.e., entry of organisms into habitats with negative effects on organisms already there. Knowing whether introduction tends to give organisms specific ecological advantages or disadvantages in their new habitats could help understand and control invasions. Even if no specific species traits are associated with introduction, introduced species might out-compete native ones just because the pool of introduced species is very large (“global competition hypothesis”). Especially in the case of intentional introduction, high initial propagule pressure might further increase the chance of establishment, and repeated introductions from different source populations might increase the fitness of introduced species through hybridization. Intentional introduction screens species for usefulness to humans and so might select for rapid growth and reproduction or carry species to suitable habitats, all which could promote invasiveness. However, trade offs between growth and tolerance might make introduced species vulnerable to extreme climatic events and cause some invasions to be transient (“reckless invader hypothesis”). Unintentional introduction may screen for species associated with human-disturbed habitats, and human disturbance of their new habitats may make these species more invasive. Introduction and natural long-distance dispersal both imply that species have neither undergone adaptation in their new habitats nor been adapted to by other species there. These two characteristics are the basis for many well-known hypotheses about invasion, including the “biotic resistance”, “enemy release”, “evolution of increased competitive ability” and “novel weapon” hypotheses, each of which has been shown to help explain some invasions. To the extent that biotic resistance depends upon local adaption by native species, altering selection pressures could reduce resistance and promote invasion (“local adaptation hypothesis”), and restoring natural regimes could reverse this effect.     

Saving camels from straws: how propagule pressure-based prevention policies can reduce the risk of biological invasion

Nonnative species that harm or have the potential to cause harm to the environment, economy, or human health are known as invasive species. Propagule pressure may be the most important factor in establishment success of nonnative species of various taxa in a variety of ecosystems worldwide, and strong evidence is emerging that propagule pressure determines both the scale of invasion extent and impact. In a limited way, the US government is applying a “propagule pressure approach” in a variety of prevention policy contexts aimed at minimizing the impact of harmful organisms. However, there are also readily apparent opportunities for enacting propagule pressure-based measures to fill current gaps in invasive species prevention and control at national, state, and local levels. An explicit focus on propagule pressure-based policies could substantially increase the effectiveness of US efforts to prevent the introduction of invasive species through by intentional and unintentional introductions. The views expressed in this paper are solely those of the authors and do not necessarily reflect those of the US government. “As the last straw breaks the laden camel’s back...” -Charles Dickens, Dombey and Son     

Linear-no-threshold is a radiation-protection standard rather than a mechanistic effect model

The linear-no-threshold (LNT) controversy covers much more than the mere discussion whether or not “the LNT hypothesis is valid”. It is shown that one cannot expect to find only one or even the only one dose–effect relationship. Each element within the biological reaction chain that is affected by ionizing radiation contributes in a specific way to the final biological endpoint of interest. The resulting dose–response relationship represents the superposition of all these effects. Till now there is neither a closed and clear picture of the entirety of radiation action for doses below some 10 mSv, nor does clear epidemiological evidence exist for an increase of risk for stochastic effects, in this dose range. On the other hand, radiation protection demands for quantitative risk estimates as well as for practicable dose concepts. In this respect, the LNT concept is preferred against any alternative concept. However, the LNT concept does not necessarily mean that the mechanism of cancer induction is intrinsically linear. It could hold even if the underlying multi-step mechanisms act in a non-linear way. In this case it would express a certain “attenuation” of non-linearities. Favouring LNT against threshold-, hyper-, or sub-linear models for radiation-protection purposes on the one hand, but preferring one of these models (e.g. for a specific effect) because of biological considerations for scientific purposes on the other hand, does not mean a contradiction.     

Sexes,species, and genomes: why males and females are not like humans and chimpanzees

This paper describes, analyzes, and critiques the construction of separate “male” and “female” genomes in current human genome research. Comparative genomic work on human sex differences conceives of the sexes as like different species, with different genomes. I argue that this construct is empirically unsound, distortive to research, and ethically questionable. I propose a conceptual model of biological sex that clarifies the distinction between species and sexes as genetic classes. The dynamic interdependence of the sexes makes them “dyadic kinds” that are not like species, which are “individual kinds.” The concept of sex as a “dyadic kind” may be fruitful as a remedy to the tendency to conceive of the sexes as distinct, binary classes in biological research on sex more generally.     

Ecological explanations for successful invasion of exotic plants

The intentional introduction of exotic species can increase the level of local biodiversity, enrich people’s material lives, and bring significant social and economic benefits that are also the symbols of human progress. However, along with the frequent intercourse among countries and regions, the frequency of uncontrolled crossregional migration of species is increased and there is a lack of scientific management strategy for the intentional introduction of exotic species. Exotic species invasion, which is behind habitat fragmentation, has become the second largest threatening factor to the maintenance of the global-scale level of biological diversity. Exotic species invasion can destroy the structure of an ecosystem, disturb the economic life of a society, and do harm to human health. In this paper, the authors review some of the ecological explanations for issues such as “what causes or mechanisms have led to the successful invasion of exotic species”, including the “ideal weeds characteristics”, “biodiversity resistance hypothesis”, “enemies release hypothesis”, “evolution of increased competitive ability hypothesis”, “niche opportunity hypothesis”, and “novel weapon hypothesis”. The authors also analyze and evaluate the background and theoretical basis of the hypotheses, providing explanations for some phenomena, as well as the deficiencies of these explanations.     

Hidden treatments in ecological experiments: re-evaluating the ecosystem function of biodiversity

Interactions between biotic and abiotic processes complicate the design and interpretation of ecological experiments. Separating causality from simple correlation requires distinguishing among experimental treatments, experimental responses, and the many processes and properties that are correlated with either the treatments or the responses, or both. When an experimental manipulation has multiple components, but only one of them is identified as the experimental treatment, erroneous conclusions about cause and effect relationships are likely because the actual cause of any observed response may be ignored in the interpretation of the experimental results. This unrecognized cause of an observed response can be considered a “hidden treatment.” Three types of hidden treatments are potential problems in biodiversity experiments: (1) abiotic conditions, such as resource levels, or biotic conditions, such as predation, which are intentionally or unintentionally altered in order to create differences in species numbers for “diversity” treatments; (2) non-random selection of species with particular attributes that produce treatment differences that exceed those due to “diversity” alone; and (3) the increased statistical probability of including a species with a dominant negative or positive effect (e.g., dense shade, or nitrogen fixation) in randomly selected groups of species of increasing number or “diversity.” In each of these cases, treatment responses that are actually the result of the “hidden treatment” may be inadvertently attributed to variation in species diversity. Case studies re-evaluating three different types of biodiversity experiments demonstrate that the increases found in such ecosystem properties as productivity, nutrient use efficiency, and stability (all of which were attributed to higher levels of species diversity) were actually caused by “hidden treatments” that altered plant biomass and productivity. Received: 16 December 1996 / Accepted: 2 March 1997     

Genes versus phenotypes in the study of speciation

Despite persistent debate on the nature of species, the widespread adoption of Mayr’s biological species concept has led to a heavy emphasis on the importance of reproductive isolation to the speciation process. Equating the origin of species with the evolution of reproductive isolation has become common practice in the study of speciation, coincident with an increasing focus on elucidating the specific genetic changes (i.e.—speciation genes) underlying intrinsic reproductive barriers between species. In contrast, some have recognized that reproductive isolation is usually a signature effect rather than a primary cause of speciation. Here we describe a research paradigm that shifts emphasis from effects to causes in order to resolve this apparent contradiction and galvanize the study of speciation. We identify major elements necessary for a balanced and comprehensive investigation of the origin of species and place the study of so-called “speciation genes” into its appropriate context. We emphasize the importance of characterizing diverging phenotypes, identifying relevant evolutionary forces acting on those phenotypes and their role in the causal origins of reduced gene flow between incipient species, and the nature of the genetic and phenotypic boundaries that results from such processes. This approach has the potential to unify the field of speciation research, by allowing us to make better “historical” predictions about the fate of diverging populations regardless of taxon.     

Poetry and Precision: Johannes Thienemann,the Bird Observatory in Rossitten and Civic Ornithology, 1900–1930

In the early twentieth century, ornithology underwent significant changes. So far, these changes, basically, have been studied by focussing on the elite of professional biologists working at universities or state museums. However, important developments also occurred in what Lynn Nyhart has called “the civic realm” of science – the sphere given form by private naturalist associations, nature writers, taxidermists and school teachers. This article studies the changing dynamics of civic ornithology, by looking at one particular case: the influential orinthological observatory in Rossitten, East-Prussia. This observatory, the first of its kind, was founded in 1901 and led, for the first three decades of its existence, by the minister Johannes Thienemann. This article analyses the ornithological practices Thienemann developed in Rossitten and the rhetoric he used to defend these practices. In both, so it is argued, one finds a mixture of the traditional, locally anchored naturalist approach with the new ideals of the “modern” and “experimental” university laboratories. The innovations which Thienemann introduced in this hybrid form of ornithology called for specific spatial strategies which made optimal use of the natural chatacteristics of his workplace and which mobilized a large civic network of geograhically scattered amateurs. At the same time, his work also altered the space he shared with the birds – materially, conceptually and culturally. Thus, this article maintains Thienemann's ornithology can only be understood by acknowledging its continuous interaction with the geographical and civic context in which it arose.     

Influence of educational levels of the spouses on consanguinity among three endogamous groups of Andhra Pradesh,South India

The highest values of consanguinity was found among “Kamma” (45.0%), “Ediga” (47.5%) and “Mala” (55.7%) who occupy different strata of Indian caste hierarchy. In the way of searchout the factors influencing consanguineous marriages, the present paper finda the negative relationship between educational levels of the spouses and consanguinity. The educational levels of men has significant effect on the frequency of consanguinious marriages among “Kamma” and “Mala”. However, further analysis deplore significant differences in the mean levels consanguinity between educational groups. It divulge low level of higher education among the populations. Only 12% of men and 1.6% of women have degree level and above education in the total sample.     

Circumscription of Malvaceae (Malvales) as determined by a preliminary cladistic analysis of morphological, anatomical, palynological, and chemical characters

We report a phylogenetic analysis of “core” Malvales (Tiliaceae, Sterculiaceae, Bombacaceae, and Malvaceae) based on morphological, anatomical, palynological, and chemical features. The results of the analyses lead to the conclusion that Tiliaceae, Sterculiaceae, and Bombacaceae, as variously delimited, are paraphyletic; only the Malvaceae are likely monophyletic. The genera of “core” Malvales form a well-defined clade. Genera of “Tiliaceae” constitute the basal complex within “core” Malvales. The “Sterculiaceae” (most genera)+ “Bombacaceae” + Malvaceae form a clade on the basis of a monadelphous androecium; “Bombacaceae”+ Malvaceae also form a clade, which is diagnosable on the basis of monoloculate anthers. It is clear that the traditional classification, with its arbitrarily delimited evolutionary grades, is unsatisfactory, especially if one seeks to reflect phylogeny accurately. Thus, Malvaceae is redefined to refer to the most recent common ancestor of plants previously considered to be “Tiliaceae,” “Sterculiaceae,” “Bombacaceae,” and Malvaceae, and all of the descendants of that ancestor. This broadly circumscribed Malvaceae can be diagnosed by several presumed synapomorphies, but we draw special attention to the unusual floral nectaries that are composed of densely packed, multicellular, glandular hairs on the sepals (or less commonly on the petals or androgynophore).     

Effects of animal density,volume, and the use of 2D/3D recording on behavioral studies of copepods

Studies on the behavior of copepods require both an appropriate experimental design and the means to perform objectively verifiable numerical analysis. Despite the growing number of publications on copepod behavior, it has been difficult to compare these studies. In this study, we studied two species of copepods, Eurytemora affinis and Pseudodiaptomus annandalei, and employed recently developed scaling and non-scaling methodology to investigate the effects of density and volume on the swimming behavior of individual organisms in still water. We also compared the results of two- and three-dimensional projections of the swimming tracks. A combination of scale-dependent and scale-independent analysis was found to characterize a number of behavioral observations very effectively. We discovered that (i) density has no effect except to increase the time spent in the swimming state of “breaking”, (ii) smaller volumes resulted in more complex trajectories, and larger volumes, like density, increased the time spent in the swimming state “breaking”, and (iii) three-dimensional projections gave a more accurate estimation of speed and the time spent cruising. When only a vertical 2D projection was used, “cruising” could be confused with “sinking”. These results indicate that both experimental conditions and the selection of 2D or 3D projection have important implications regarding the study of copepod behavior. The development of standardized procedures with which to compare the observations made in different studies is an issue of particular urgency.     

Unique Determination of Some Homoplasies at Hybridization Events

Phylogenetic relationships may be represented by rooted acyclic directed graphs in which each vertex, corresponding to a taxon, possesses a genome. Assume the characters are all binary. A homoplasy occurs if a particular character changes its state more than once in the graph. A vertex is “regular” if it has only one parent and “hybrid” if it has more than one parent. A “regular path” is a directed path such that all vertices after the first are regular. Assume that the network is given and that the genomes are known for all leaves and for the root. Assume that all homoplasies occur only at hybrid vertices and each character has at most one homoplasy. Assume that from each vertex there is a regular path leading to a leaf. In this idealized setting, with other mild assumptions, it is proved that the genome at each vertex is uniquely determined. Hence, for each character the vertex at which a homoplasy occurs in the character is uniquely determined. Without the assumption on regular paths, an example shows that the genomes and homoplasies need not be uniquely determined.     

The structure of social behaviour inTheropithecus gelada

Through the use of principal components analysis of the correlation matrix between excentricity quotients of intra- and inter-individual transitions between pairs of the 22 most frequent behaviour elements of male and female gelada baboons observed in captivity, the total variance could be described in terms of a low number of causal factors. In intra-individual sequences the five factors requested of the analysis explain 74 per cent of the total variance. The following intra-individual groupings were found: (I) “autostimulation”, (II) “intensive social” versus “groom”, (III) “male sexual”, (IV) “attack” versus “sexual presentation”, and (V) “greeting” versus “threat”. In inter-individual transitions, the five factors explain 68 per cent of the variance. The following communicative sets were found: (1) “female-sexual releasing”, (2) “greeting and approaching releasing” versus “groom releasing”, (3) “austostimulation releasing” versus “male-sexual releasing”, (4) “fight releasing”, and (5) “conflict”. Mimetic induction of same acts or acts within one particular intra-individual set was frequent.     

About a possible role of parasomnias as a factor of stabilization of sleep cycles

Cyclical organization of sleep is one of necessary conditions of normal human and animal life activity and one of basic manifestations of the circadian cycle. Transition from the slowwave to the paradoxical sleep is often accompanied by brief, sometimes rhythmical motor and autonomic reactions that do not cause awakening, but seem to promote activation of the mechanisms providing the “switch” of the sleep phases. Immaturity (or a lesion) of the neurophysiologic mechanisms responsible for the “switch” of the sleep stages leads to hindering of alternation of the sleep phases, which disturbs their normal sequence and leads to deficit of reparative and homeostatic processes. This is manifested as deterioration of the neuropsychical state during wakefulness. The data are presented which allow suggesting that the stereotypical motor or autonomic reactionspathological parasomnias, for instance enuresis, can appear as a compensatory mechanism promoting the sleep phase switch. Episodes of the pathological parasomnias promote normalization of the sleep stage alternation and thereby affect positively recovery of its cyclical organization.     

Helix-mediated protein–protein interactions as targets for intervention using foldamers

Protein–protein interactions (PPIs) play a central role in virtually all biological processes and have been the focus of intense investigation from structural molecular biology to cell biology for the majority of the last two decades and, more recently, are emerging as important targets for pharmaceutical intervention. A common motif found at the interface of PPIs is the α-helix, suggesting that, in the same way as the “lock and key” model has evolved for competitive inhibition of enzymes, it should be possible to elaborate “rule-based” approaches for inhibition of helix-mediated PPIs. This review will describe the biological function and structural features of a series of representative helix-mediated PPIs and discuss approaches that are being developed to target these interactions with small molecules that employ non-natural amino acids.     

The Evolution of Evolution: Reconciling the Problem of Stability

Evolutionary Science has, at least since the publication of Origin, been less concerned with the continuation of species in stable forms, than with the reconfiguration of forms into a host of varieties. So influential has this emphasis been that, over the years, “variation” has become a cardinal desideratum, even taking precedence over the macroevolutionary landscape. This orientation has made it much more difficult to objectively assess the meaning of non-change patterns such as periods of stasis, which appear to be widespread in most species. Yet, if stasis is an expectable outcome of evolutionary activity, this raises the possibility that there may be mechanisms and processes at many causal levels, acting on its behalf, without reference to the impetus toward persistent variation. Researchers have been reluctant to attribute stasis to a macroevolutionary tendency toward ‘stability’ despite the commonality of stasis in many species, and notwithstanding the many biological/behavioral processes that seem inclined to produce and maintain conformance, regulation and consistency. Speciation, paradoxically, is the best evidence for an overriding influence toward stability in that stability would seem to be a necessary condition prior to the development of isolating mechanisms. An alternative macroevolutionary model of biological activity is offered consisting of two tendencies, “variety” counterpoised with “stability” both acting in the service of the persistence of life.     

Sagas of the Children of Time: The Importance of Phylogenetic Teaching in Biology

Theodosius Dobznahnsky said nothing in biology makes sense except in the light of evolution. Nothing in evolution makes sense except in the light of the historical emergence of species. Species are the biological “children of time.” If we seek to understand them, historical narratives are essential elements of our causal explanations. Phylogenetic systematic analysis provides the Rosetta Stone for uncovering that narrative.