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941.
Sun Hwa Hong Sun Ah Choi Myung-Hyun Lee Bo Ra Min Cheolho Yoon Hyeon Yoon Kyung-Suk Cho 《Environmental geochemistry and health》2011,33(1):41-47
The effects of arsenic (As) species, such as As(III), As(V) and dimethylarsinic acid (DMA), on the accumulation of As in cucumber (Cucumis sativus), as well as on its growth in a soil mesocosm were evaluated. When Cucumis sativus was cultivated in soils contaminated with 20 and 50 mg/kg of As(III), As(V) or DMA for 40 days, the growth was markedly inhibited by the inorganic As (As(III) and As(V)) rather than the organic As (DMA). Irrespective of the As species, the As concentrations accumulated in Cucumis sativus increased with increasing As concentration in the soil. The As bioaccumulation factors from soil into the tissue of Cucumis sativus were 17.5–35.4, 29.3–42.7 and 17.6–25.7 for As(III), As(V) and DMA, respectively. In addition, the As translocation factors from the roots to shoots were 0.025–0.031, 0.018–0.032 and 0.014–0.026 for As(III), As(V) and DMA, respectively. In conclusion, Cucumis sativus mainly accumulated As in its roots rather than its shoots and easily accumulated inorganic rather than organic As from the soil into its tissue. 相似文献
942.
Chiang CT Chang TK Hwang YH Su CC Tsai KY Yuan TH Lian IeB 《Environmental geochemistry and health》2011,33(5):469-476
The growing incidence of oral cancer (OC) in Taiwan has become a crucial public health concern. In particular, Changhua, a
county in central Taiwan, carries persistently high OC incidence rate, with an alarmingly high male/female ratio of OC incidence.
Previous epidemiological studies had found that the incidence is spatially correlated with the level of soil content to certain
heavy metals in the central Taiwan area. Soil and the human body both intake environmental heavy metals, which can be absorbed
through various ways. The soil metal concentration is an index of possible environmental exposure to heavy metal, and the
blood metal concentration somewhat reflects the level of the exposure on the human body. Metallic carcinogen is likely to
generate free radicals and play a role in many cancers, and many studies had reported that environmental exposure to heavy
metals is an important risk factor for developing cancer. Studies on animals showed that chronic intake of chromium (Cr) could
induce OC. This study aims to explore the association between the Cr concentration in the farm soil and in the blood of OC
patients. We recruited 79 OC patients from Changhua County, with their lifestyle being adjusted in regression analysis. The
results showed that the Cr concentration in the blood of OC patients is significantly higher than the background value, and
is positively associated with the Cr concentration in the soil surrounding their residence (p-value < 0.023). Because Changhua County is only with moderate prevalence of the known OC habitual risk factors, an environmental
factor related to heavy metal Cr exposure is suspected. Future investigations may verify the causal relation between Cr and
OC. 相似文献
943.
The concept of evolvability is controversial. To some, it is simply a measure of the standing genetic variation in a population
and can be captured by the narrow-sense heritability (h2). To others, evolvability refers to the capacity to generate heritable phenotypic variation. Many scientists, including Darwin,
have argued that environmental variation can generate heritable phenotypic variation. However, their theories have been difficult
to test. Recent theory on the evolution of sex and recombination provides a much simpler framework for evaluating evolvability.
It shows that modifiers of recombination can increase in prevalence whenever low fitness individuals produce proportionately
more recombinant offspring. Because recombination can generate heritable variation, stress-induced recombination might be
a plausible mechanism of evolvability if populations exhibit a negative relationship between fitness and recombination. Here
we use the fruit fly, Drosophila melanogaster, to test for this relationship. We exposed females to mating stress, heat shock or cold shock and measured the temporary
changes that occurred in reproductive output and the rate of chromosomal recombination. We found that each stress treatment
increased the rate of recombination and that heat shock, but not mating stress or cold shock, generated a negative relationship
between reproductive output and recombination rate. The negative relationship was absent in the low-stress controls, which
suggests that fitness and recombination may only be associated under stressful conditions. Taken together, these findings
suggest that stress-induced recombination might be a mechanism of evolvability. 相似文献
944.
In ecological and behavioral research, drawing reliable conclusions from statistical models with multiple predictors is usually
difficult if all predictors are simultaneously in the model. The traditional way of handling multiple predictors has been
the use of threshold-based removal-introduction algorithms, that is, stepwise regression, which currently receives considerable
criticism. A more recent and increasingly propagated modelling method for multiple predictors is the information theoretic
(IT) approach that quantifies the relative suitability of multiple, potentially non-nested models based on a balance of model
fit and the accuracy of estimates. Here, we examine three shortcomings of stepwise regression, subjective critical values,
model uncertainty, and parameter estimation bias, which have been suggested to be avoided by applying information theory.
We argue that, in certain circumstances, the IT approach may be sensitive to these issues as well. We point to areas where
further testing and development could enhance the performance of IT methods and ultimately lead to robust inferences in behavioral
ecology. 相似文献
945.
Judith Morales Alberto Velando Roxana Torres 《Behavioral ecology and sociobiology》2011,65(2):197-203
Avian eggshell color is remarkably variable among and within species and its possible function has long been controversial.
Female birds use biliverdin pigment to color their eggs blue and green. Although evidence is accumulating that blue-green
eggshell coloration is costly to produce, the exact mechanisms underlying its expression are little studied. Biliverdin pigment
is involved in important maintenance functions such as immune and antioxidant defenses and shows similar properties to carotenoid
pigments. Carotenoids play a role as immunoenhancers and have the potential to ameliorate the impact of oxidative processes,
although their antioxidant function could be minor for some bird species. Important life-history components can be limited
by carotenoid availability, including sexual displays and fecundity. Here we explored if biliverdin-based eggshell pigmentation
was affected by carotenoid availability in a seabird, by performing a carotenoid supplementation experiment in female blue-footed
boobies (Sula nebouxii) after laying their first egg. In this species, blue eggshell color is associated with incubation patterns, and carotenoid
availability affects the crucial trade-off between female foot ornamentation and fecundity. We found that under natural conditions,
there was a decline in eggshell color with laying order, suggesting pigment limitation for females. However, carotenoid-supplemented
females had enhanced second egg coloration compared to controls, and the color increase was independent of their previous
pigment allocation to the first egg. Our results suggest that biliverdin-based eggshell coloration is costly to produce and
can be alleviated by current carotenoid availability. 相似文献
946.
Alex Kacelnik Marco Vasconcelos Tiago Monteiro Justine Aw 《Behavioral ecology and sociobiology》2011,65(3):547-558
Charles Darwin aided his private decision making by an explicit deliberation, famously deciding whether or not to marry by
creating a list of points in a table with two columns: “Marry” and “Not Marry”. One hundred seventy-two years after Darwin’s
wedding, we reconsider whether this process of choice, under which individuals assign values to their options and compare
their relative merits at the time of choosing (the tug-of-war model), applies to our experimental animal, the European Starling,
Sturnus vulgaris. We contrast this with the sequential choice model that postulates that decision-makers make no comparison between options
at the time of choice. According to the latter, behaviour in simultaneous choices reflects adaptations to contexts with sequential
encounters, in which the choice is whether to take an opportunity or let it pass. We postulate that, in sequential encounters,
the decision-maker assigns (by learning) a subjective value to each option, reflecting its payoff relative to background opportunities.
This value is expressed as latency and/or probability to accept each opportunity as opposed to keep searching. In simultaneous
encounters, choice occurs through each option being processed independently, by a race between the mechanisms that generate
option-specific latencies. We describe these alternative models and review data supporting the predictions of the sequential
choice model. 相似文献
947.
In most birds, natal dispersal is female-biased, but the selective pressures leading to this pattern have rarely been explored
with comprehensive data on lifetime reproductive success. In territorial birds, the benefit of philopatry should be higher
for males than for females when males establish territories for which knowledge about the local environment is important.
As females may use male characteristics for mate choice, and hence indirectly for territory choice, the benefit from the direct
knowledge of the local environment may be lower for females than males. We tested this hypothesis using data from a long-term
study of group living corvids, the Siberian jays (Perisoreus infaustus). In this species, the socially dominant offspring delay dispersal while the sub-dominant offspring leave the family group
directly after reaching independence. Our results show that natal dispersal distance (a proxy for local knowledge) was related
to sex and dispersal timing (a proxy for “quality”): Females and early dispersers traveled further on average than males and
delayed dispersers. Furthermore, dispersal distance and timing were negatively related to the number of recruits produced
over an individual’s lifetime in males, but not in females. Hence, the results support the hypothesis that the female-biased
natal dispersal found in this and other bird species may come about through higher lifetime reproductive success of philopatric
males than females. 相似文献
948.
Recent attempts to integrate function and mechanism have resulted in an appreciation of the relevance of forager psychology
to understanding the functional aspects of foraging behaviour. Conversely, an acknowledgement of the functional diversity
of learning mechanisms has led to greater understanding of the adaptive nature of cognition. In this paper, we present data
from three experiments suggesting that noisy miner birds use different cognitive strategies when searching for foods with
different distributions. When searching for nectar, an immobile, readily depleted resource, birds spontaneously attend to
fine-scale spatial information and use a spatial memory-based strategy that is efficient in a novel context and largely resistant
to disruptions to movement. When searching for invertebrates, a mobile, clumped and cryptic resource, birds employ a strategy
whose efficiency increases with increased task familiarity, is vulnerable to disruptions to their movement and may rely more
on memory for movement rules than memory for location information. Previous reports of adapted cognition have reported performance
differences between species (for example, better spatial cognitive performance in storing versus non-storing birds). Ours
is the first study to demonstrate that differences in cognitive strategy (as opposed to just enhanced performance) occur within
a single species in different foraging contexts. As well as providing an example of how specially adapted cognitive mechanisms
might work, our data further emphasise the importance of jointly considering functional and mechanistic aspects to fully understand
the adaptive complexities of behaviour. 相似文献
949.
Donald B. Thompson 《Journal of Agricultural and Environmental Ethics》2011,24(2):165-194
The term natural is effective in the marketing of a wide variety of foods. This ambiguous term carries important meaning in Western culture.
To challenge an uncritical understanding of natural with respect to food and to explore the ambiguity of the term, the development of Western ideas of nature is first discussed. Personification and hypostasization of nature are given special emphasis. Leo Marx’s idea of the pastoral
design in literature is then used to explore the meaning of natural as applied to food, emphasizing Marx’s distinction between
a sentimental and a complex pastoral. The latter is applied to natural as a means of collapsing a dichotomy of man and nature to the idea of second nature. From this perspective an understanding of the industrialization of the food system and the importance of local and organic
food are considered. The extent to which processed foods might properly be considered natural is raised and discussed for
several common foods. Although marketing of natural foods might make us think that we consume nature, I suggest that what
is consumed is more appropriately second nature. I suggest that in order to maintain a critical perspective about one’s relationship
to the natural world, everyone should make an attempt to experience the complex pastoral with respect to at least something
that is consumed as food. When nature is understood as second nature in the context of a complex pastoral, the question of
whether a food or ingredient is to be considered natural is replaced by deliberative thought based on our best knowledge and
judgment, and the result will be less constrained by ideology. 相似文献
950.
Mohammad Aslam Khan S. Akhtar Ali Shah 《Journal of Agricultural and Environmental Ethics》2011,24(5):493-509
There is evidence of continued food insecurity and malnutrition in Pakistan despite significant progress made in terms of
food production in recent years. According to “Vision 2030” of the Planning Commission of Pakistan, about half of the population
in the country suffers from absolute to moderate malnutrition, with the most vulnerable being children, women, and elderly
among the lowest income group. The Government of Pakistan has been taking a series of policy initiatives and strategic measures
to combat food insecurity issues. These range from increasing production to food imports, implementation of poverty reduction
strategies, nutritional improvement programs, as well as provision of social safety nets. The article aims to instill some
fresh thinking into the debate regarding the challenges of food security. It underscores the limitations of hitherto policy
response, and suggests crucial measures to improve the present grim scenario. Policy makers, planners, practitioners, and
academicians in countries with comparable socio-political and economic setup can view this discussion as a case study and
may apply the findings in their domain accordingly. 相似文献