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12,010 result(s) for "life history theory"
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Oxidative stress and life histories: unresolved issues and current needs
Life‐history theory concerns the trade‐offs that mold the patterns of investment by animals between reproduction, growth, and survival. It is widely recognized that physiology plays a role in the mediation of life‐history trade‐offs, but the details remain obscure. As life‐history theory concerns aspects of investment in the soma that influence survival, understanding the physiological basis of life histories is related, but not identical, to understanding the process of aging. One idea from the field of aging that has gained considerable traction in the area of life histories is that life‐history trade‐offs may be mediated by free radical production and oxidative stress. We outline here developments in this field and summarize a number of important unresolved issues that may guide future research efforts. The issues are as follows. First, different tissues and macromolecular targets of oxidative stress respond differently during reproduction. The functional significance of these changes, however, remains uncertain. Consequently there is a need for studies that link oxidative stress measurements to functional outcomes, such as survival. Second, measurements of oxidative stress are often highly invasive or terminal. Terminal studies of oxidative stress in wild animals, where detailed life‐history information is available, cannot generally be performed without compromising the aims of the studies that generated the life‐history data. There is a need therefore for novel non‐invasive measurements of multi‐tissue oxidative stress. Third, laboratory studies provide unrivaled opportunities for experimental manipulation but may fail to expose the physiology underpinning life‐history effects, because of the benign laboratory environment. Fourth, the idea that oxidative stress might underlie life‐history trade‐offs does not make specific enough predictions that are amenable to testing. Moreover, there is a paucity of good alternative theoretical models on which contrasting predictions might be based. Fifth, there is an enormous diversity of life‐history variation to test the idea that oxidative stress may be a key mediator. So far we have only scratched the surface. Broadening the scope may reveal new strategies linked to the processes of oxidative damage and repair. Finally, understanding the trade‐offs in life histories and understanding the process of aging are related but not identical questions. Scientists inhabiting these two spheres of activity seldom collide, yet they have much to learn from each other. The physiological basis of life history trade‐offs remains elusive. One idea is that oxidative stress may be an important consequence of reproduction that links it to reduced survival. Recent work however has produced a large amount of conflicting data. We present a potential route out of the quagmire.
Knowledge and the early modern city : a history of entanglements
\"Knowledge and the Early Modern City uses case studies from the sixteenth to the eighteenth centuries to examine the relationships between knowledge and the city and how these changed in a period when the nature and conception of both was drastically transformed. Providing the ideal starting point for those seeking to understand the role of urban institutions, actors and spaces in the production of knowledge and the development of the so-called 'modern' knowledge society, this is the perfect resource for students and scholars of early modern history and knowledge\"-- Provided by publisher.
The sculpting of somatic mutational landscapes by evolutionary forces and their impacts on aging‐related disease
Aging represents the major risk factor for the development of cancer and many other diseases. Recent findings show that normal tissues become riddled with expanded clones that are frequently driven by cancer‐associated mutations in an aging‐dependent fashion. Additional studies show how aged tissue microenvironments promote the initiation and progression of malignancies, while young healthy tissues actively suppress the outgrowth of malignant clones. Here, we discuss conserved mechanisms that eliminate poorly functioning or potentially malignant cells from our tissues to maintain organismal health and fitness. Natural selection acts to preserve tissue function and prevent disease to maximize reproductive success but these mechanisms wane as reproduction becomes less likely. The ensuing age‐dependent tissue decline can impact the shape and direction of clonal somatic evolution, with lifestyle and exposures influencing its pace and intensity. We also consider how aging‐ and exposure‐dependent clonal expansions of “oncogenic” mutations might both increase cancer risk late in life and contribute to tissue decline and non‐malignant disease. Still, we can marvel at the ability of our bodies to avoid cancers and other diseases despite the accumulation of billions of cells with cancer‐associated mutations. Pathogenic clonal expansions can promote and be promoted by inflammation, and contribute to multiple diseases of aging. While these clones can sometimes directly contribute to malignant disease, as clearly demonstrated for leukemias with clonal hematopoiesis mutations, evidence also reveals how clonal expansions can contribute indirectly to cancers and non‐malignant diseases such as through the promotion of inflammation.
Integrating the pace‐of‐life syndrome across species, sexes and individuals: covariation of life history and personality under pesticide exposure
The pace‐of‐life syndrome (POLS) hypothesis integrates covariation of life‐history traits along a fast–slow continuum and covariation of behavioural traits along a proactive–reactive personality continuum. Few studies have investigated these predicted life‐history/personality associations among species and between sexes. Furthermore, whether and how contaminants interfere with POLS patterns remains unexplored. We tested for covariation patterns in life history and in behaviour, and for life‐history/personality covariation among species, among individuals within species and between sexes. Moreover, we investigated whether pesticide exposure affects covariation between life history and behaviour and whether species and sexes with a faster POLS strategy have a higher sensitivity to pesticides. We reared larvae of four species of Ischnura damselflies in a common garden experiment with an insecticide treatment (chlorpyrifos absent/present) in the final instar. We measured four life‐history traits (larval growth rate during the pesticide treatment, larval development time, adult mass and life span) and two behavioural traits (larval feeding activity and boldness, each before and after the pesticide treatment). At the individual level, life‐history traits and behavioural traits aligned along a fast–slow and a proactive–reactive continuum, respectively. Species‐specific differences in life history, with fast‐lived species having a faster larval growth and development, a lower mass at emergence and a shorter life span, suggested that time constraints in the larval stage were predictably driving life‐history evolution both in the larval stage and across metamorphosis in the adult stage. Across species, females were consistently more slow‐lived than males, reflecting that a large body size and a long life span are generally more important for females. In contrast to the POLS hypothesis, there was only little evidence for the expected positive coupling between life‐history pace and proactivity. Pesticide exposure decreased larval growth rate and affected life‐history/personality covariation in the most fast‐lived species. Our study supports the existence of life‐history and behavioural continua with limited support for life‐history/personality covariation. Variation in digestive physiology may explain this decoupling of life history and behaviour and provide valuable mechanistic insights to understand and predict the occurrence of life‐history/personality covariation patterns.
Republic of women : rethinking the Republic of Letters in the seventeenth century
\"Republic of Women recaptures a lost chapter in the narrative of intellectual history. It tells the story of a transnational network of female scholars who were active members of the seventeenth-century republic of letters and demonstrates that this intellectual commonwealth was a much more eclectic and diverse assemblage than has been assumed. These seven scholars - Anna Maria van Schurman, Princess Elisabeth of Bohemia, Marie de Gournay, Marie du Moulin, Dorothy Moore, Bathsua Makin and Katherine Jones, Lady Ranelagh - were philosophers, schoolteachers, reformers and mathematicians. They hailed from England, Ireland, Germany, France and The Netherlands. And together with their male colleagues - men like Descartes, Huygens, Hartlib and Montaigne - they represented the spectrum of contemporary approaches to science, faith, politics and the advancement of learning. Carol Pal uses their collective biography to reconfigure the intellectual biography of early modern Europe, offering a new, expanded analysis of the seventeenth-century community of ideas\"-- Provided by publisher.
Effects of life history and reproduction on recruitment time lags in reintroductions of rare plants
Reintroductions are important components of conservation and recovery programs for rare plant species, but their long-term success rates are poorly understood. Previous reviews of plant reintroductions focused on short-term (e.g.,≤3 years) survival and flowering of founder individuals rather than on benchmarks of intergenerational persistence, such as seedling recruitment. However, short-term metrics may obscure outcomes because the unique demographic properties of reintroductions, including small size and unstable stage structure, could create lags in population growth. We used time-to-event analysis on a database of unusually well-monitored and long-term (4–28 years) reintroductions of 27 rare plant species to test whether life-history traits and population characteristics of reintroductions create time-lagged responses in seedling recruitment (i.e., recruitment time lags [RTLs]), an important benchmark of success and indicator of persistence in reintroduced populations. Recruitment time lags were highly variable among reintroductions, ranging from <1 to 17 years after installation. Recruitment patterns matched predictions from life-history theory with short-lived species (fast species) exhibiting consistently shorter and less variable RTLs than longlived species (slow species). Long RTLs occurred in long-lived herbs, especially in grasslands, whereas short RTLs occurred in short-lived subtropical woody plants and annual herbs. Across plant life histories, as reproductive adult abundance increased, RTLs decreased. Highly variable RTLs were observed in species with multiple reintroduction events, suggesting local processes are just as important as life-history strategy in determining reintroduction outcomes. Time lags in restoration outcomes highlight the need to scale success benchmarks in reintroduction monitoring programs with plant life-history strategies and the unique demographic properties of restored populations. Drawing conclusions on the long-term success of plant reintroduction programs is premature given that demographic processes in species with slow life-histories take decades to unfold. Las reintroducciones son componentes importantes de los programas de conservación y recuperación de especies raras de plantas, pero las tasas de éxito a largo plazo cuentan con muy poco entendimiento. Las revisiones previas de las reintroducciones de plantas se han enfocado en la supervivencia a corto plazo (p. ej.: ≤ 3años) y en el florecimiento de individuos fundadores en lugar de enfocarse en puntos de referencia para la persistencia inter-generacional, como el reclutamiento de plántulas. Sin embargo, las medidas a corto plazo pueden ocultar los resultados ya que las propiedades demográficas únicas de las reintroducciones, incluyendo el menor tamaño y la estructura inestable de estadio, podrían crear demoras en el crecimiento poblacional. Usamos un análisis de tiempo-para-evento en una base de datos de reintroducciones inusualmente bien monitoreadas y de largo plazo (4–28 años) de 27 especies raras de plantas para probar si los atributos de la historia de vida y las características poblacionales de la reintroducción crean respuestas con demoras temporales en el reclutamiento de plántulas (es decir, demoras temporales en el reclutamiento), un punto de referencia importante para el éxito y un indicador de la persistencia en poblaciones reintroducidas. Las demoras temporales de reclutamiento (RTLs, en inglés) fueron muy variables entre las reintroducciones, abarcando desde < 1 hasta 17 años después de la instalación. Los patrones de reclutamiento se acoplaron a las predicciones de la teoría de historias de vida, donde las especies de vida corta (especies rápidas) exhibieron RTLs consistentemente más cortas y menos variables que las especies de vida larga (especies lentas). Las RTLs largas ocurrieron en hierbas de vida larga, especialmente en los pastizales, mientras que las RTLs cortas ocurrieron en plantas leñosas subtropicales de vida corta y en hierbas anuales. En todas las historias de vida de las plantas, conforme incrementó la abundancia de adultos reproductivos, las RTLs disminuyeron. Se observaron RTLs altamente variables en las especies con eventos de reintroducción múltiples, lo que sugiere que los procesos locales son igual de importantes que la estrategia de historia de vida para determinar los resultados de las reintroducciones. Las demoras temporales en los resultados de restauración resaltan la necesidad de poner a escala los puntos de referencia de éxito en los programas de monitoreo de reintroducciones que tengan estrategias de historia de vida de las plantas y las propiedades demográficas únicas de las poblaciones restauradas. La obtención de conclusiones sobre el éxito a largo plazo de los programas de reintroducción de plantas es algo prematuro ya que los procesos demográficos de especies con historias de vida lentas tardan décadas en desarrollarse. 重引入是稀有植物保护和恢复计划的ー个重要组成部分,担其长期的成功率仍不得而知。对檀物重引 人已有的综述主要关注引人个体短期_ 三年内) 的存活和开花情况而不是以其跨代续存(Mi幼苗更新)为基 准。然而,短期指标可能会掩盖真实結果,因为重引入物种有独特的种群统计特征,包括小种群和不稳定的阶段 结构,可能导致种群增长存在滞后。我们用时间-事件分析法,对开展了非常好的监测的2 7 种长期(4 - 28年)重 引人植物的监测数据进行分析,检验了重引入物种的生活史特性和种群特征是否会导致幼苗更新存在时间滞后 响应(即更新时滞),这是重引入成功与否的重要基准,也是重引入种群续存的ー项指标。不同的重引入物种更 新时滞(recruitment time lags, RTL)差异很大,变化范围从栽种后不到一年到长达十七年。更新模式与生活史 理论预测结果相吻合,即相比于寿命长(生长慢) 的物种,寿命短(生长快) 的物种JRTL都更短、变异也更小。寿 命长的草本植物RTL长,特别是草原上的物种,而寿命短的亚热带木本植物及一年生草本植物RTL则较短。在植 物整个生活史中,JRTL随着可繁殖成体的数量增加而下降。有多次重引人事件的物种RTL变异较大,这表明局部过程与生活史策略在决定重引入结果上同等重要。恢复结果时滞效应的存在强调了利用恢复种群的植物生活史 策略及特殊的种群统计特征来衡量重引人监测项目成功与否的必要性。鉴于生活史慢的物种可能需要几十年的 时间来完成种群统计过程,对植物重引人项目的长期成功下定论尚为时过早。
Laughter in ancient Rome : on joking, tickling, and cracking up
\"What made the Romans laugh? Was ancient Rome a carnival, filled with practical jokes and hearty chuckles? Or was it a carefully regulated culture in which the uncontrollable excess of laughter was a force to fear- a world of wit, irony, and knowing smiles? How did Romans make sense of laughter? What role did it play in the world of the law courts, the imperial palace, or the spectacles of the arena? Laughter in Ancient Rome explores one of the most intriguing, but also trickiest, of historical subjects. Drawing on a wide range of Roman writing- from essays on rhetoric to a surviving Roman joke book- Mary Beard tracks down the giggles, smirks, and guffaws of the ancient Romans themselves. From ancient 'monkey business' to the role of a chuckle in a culture of tyranny, she explores Roman humor from the hilarious, to the momentous, to the surprising. But she also reflects on even bigger historical questions. What kind of history of laughter can we possibly tell? Can we ever really 'get' the Romans' jokes?\"-- Provided by publisher.
Variation in the vital rates of an Antarctic marine predator
Variation in life-history traits such as lifespan and lifetime reproductive output is thought to arise, in part, due to among-individual differences in the underlying probabilities of survival and reproduction. However, the stochastic nature of demographic processes can also generate considerable variation in fitness-related traits among otherwise-identical individuals. An improved understanding of life-history evolution and population dynamics therefore depends on evaluating the relative role of each of these processes. Here, we used a 33-yr data set with reproductive histories for 1,274 female Weddell seals from Erebus Bay, Antarctica, to assess the strength of evidence for among-individual heterogeneity in the probabilities of survival and reproduction, while accounting for multiple other sources of variation in vital rates. Our analysis used recent advances in Bayesian model selection techniques and diagnostics to directly compare model fit and predictive power between models that included individual effects on survival and reproduction to those that did not. We found strong evidence for costs of reproduction to both survival and future reproduction, with breeders having rates of survival and subsequent reproduction that were 3% and 6% lower than rates for non-breeders. We detected age-related changes in the rates of survival and reproduction, but the patterns differed for the two rates. Survival rates steadily declined from 0.92 at age 7 to 0.56 at the maximal age of 31 yr. In contrast, reproductive rates increased from 0.68 at age 7 to 0.79 at age 16 and then steadily declined to 0.37 for the oldest females. Models that included individual effects explained more variation in observed life histories and had better estimated predictive power than those that did not, indicating their importance in understanding sources of variation among individuals in life-history traits. We found that among-individual heterogeneity in survival was small relative to that for reproduction. Our study, which found patterns of variation in vital rates that are consistent with a series of predictions from life-history theory, is the first to provide a thorough assessment of variation in important vital rates for a long-lived, high-latitude marine mammal while taking full advantage of recent developments in model evaluation.