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1.
Influence of hydrology and seasonality on DOC exports from three contrasting upland catchments 总被引:2,自引:0,他引:2
J. J. C. Dawson C. Soulsby D. Tetzlaff M. Hrachowitz S. M. Dunn I. A. Malcolm 《Biogeochemistry》2008,90(1):93-113
Variation in dissolved organic carbon (DOC) concentrations of surface waters is a consequence of process changes in the surrounding
terrestrial environment, both within annual cycles and over the longer term. Long-term records (1987–2006) of DOC concentrations
at six catchments (0.44–10.0 km2) across a climatic transect in Scotland were investigated for intra-annual relationships to evaluate potential long-term
seasonal patterns. The intra-annual mode of DOC export contrasted markedly between catchments and appeared dependent on their
hydrological characteristics. Catchments in wetter Central Scotland with high rainfall–runoff ratios, short transit times
and well-connected responsive soils show a distinct annual periodicity in DOC concentrations throughout the long-term datasets.
Increased DOC concentrations occurred between June and November with correspondingly lower DOC concentrations from December
to May. This appears unrelated to discharge, and is dependent mainly on higher temperatures driving biological activity, increasing
decomposition of available organic matter and solubility of DOC. The drier eastern catchments have lower rainfall–runoff ratios,
longer transit times and annual drying–wetting regimes linked to changing connectivity of soils. These are characterised by
seasonal DOC concentration–discharge relationships with an autumnal flush of DOC. Temperature influences the availability
of organic matter for DOC transport producing a high DOC concentration–discharge relationship in summer/autumn and low DOC
concentration–discharge relationship in winter/spring. These two distinct modes of seasonal DOC transport have important implications
for understanding changes in DOC concentrations and export brought about by climate change (temperature and precipitation)
and modelling of aquatic carbon losses from soil-types under different hydrological regimes. 相似文献
2.
Ewa Ziętkiewicz Vania Yotova Michal Jarnik Maria Korab-Laskowska Kenneth K. Kidd David Modiano Rosaria Scozzari Mark Stoneking Sarah Tishkoff Mark Batzer Damian Labuda 《Journal of molecular evolution》1998,47(2):146-155
Neutral DNA polymorphisms from an 8-kb segment of the dystrophin gene, previously ascertained in a worldwide sample (n= 250 chromosomes), were used to characterize the population ancestral to the present-day human groups. The ancestral state
of each polymorphic site was determined by comparing human variants with their orthologous sites in the great apes. The ``age
before fixation' of the underlying mutations was estimated from the frequencies of the new alleles and analyzed in the context
of these polymorphisms' distribution among 13 populations from Africa, Europe, Asia, New Guinea, and the Americas (n= 860 chromosomes in total). Seventeen polymorphisms older tan 100,000–200,000 years, which contributed ∼90% to the overall
nucleotide diversity, were common to all human groups. Polymorphisms endemic to human groups or continentally restricted were
younger than 100,000–200,000 years. Africans (six populations) with 13 such sites stood out from the rest of the world (seven
populations), where only 2 population-specific variants were observed. The similarity of the frequencies of the old polymorphisms
in Africans and non-Africans suggested a similar profile of genetic variability in the population before the modern human's
divergence. This ancestral population was characterized by an effective size of about 10,000 as estimated from the nucleotide
diversity; this size may describe the number of breeding individuals over a long time during the Middle Pleistocene or reflect
a speciation bottleneck from an initially larger population at the end of this period.
Received: 3 February 1998 / Accepted: 9 February 1998 相似文献
3.
Studies that have examined the effect of experimental increases in predation risk on diet selectivity have shown both decreased
and increased diet selectivity. A possible explanation for these disparate results emerges from an examination of the prey
sets used in these studies, which differed in the relationship between the values of risk components associated with the capture
of different prey types (‘danger’) and their profitabilities. When less profitable prey were more dangerous, selectivity increased
with predation risk. When prey were equally dangerous, selectivity did not change. Finally, when the more profitable prey
were also more dangerous, selectivity decreased with risk. Here, we examine theoretically the influence of a forager's estimate
of the probability that a predator is present (φ) on the selection of diets from prey sets with varying danger–profitability
relationships. A dynamic programming model is used to determine the maximum attack time (or distance) for each of two types
of prey, differing in their energetic content, for a range of forager energy state and φ levels. The diets which would result
if foragers attacked prey according to the rules provided by the dynamic model are then determined. The model results indicate
that the prey danger–profitability relationship determines the diet selectivity response to φ, confirming that variation in
this relationship could be responsible for the range of experimental results.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
Relationships of respiratory areas (gill, body surface and fin areas) (A) to body mass (W) were determined with a marine teleost,
the porgyPagrus major of 0.0002–1230 g (just after hatch to 3+ years old), based on the allometric formula A=αWβ. (1) Early larvae (0.0002–0.0003 g) did not have the secondary lamellae that were responsible for gas exchange at the gills.
After this stage, a tetraphasic relationship was observed between lamellar area (total area of secondary lamellae, often called
gill area) (GAL) and boby mass. During the late larval and early juvenile stages, the GAL-W relationship showed a triphasic positive allometry with β-values of 3.773, 1.561 and 1.111 corresponding to the first half
of the late larval stage (0.00034–0.001g), the second half of the stage (0.001–0.01 g) and the early juvenile stage (0.02–0.1
g), respectively, During the squamated juvenile and later stages (0.1–1080g), there was a negative allometry with a β-value
of 0.813. (2) A triphasic relationship was observed between the total cutaneous surface area (body surface area and fin area)
(CAb+f) and body mass. During the early larval stage, in which an increase of body mass was very small. from 0.0002 to 0.00025 g,
CAb+p/W increased with growth with a β-value of 3.986. After this stage, the CAb+t W relationship showed a diphasic negative allometry with β-values of 0.562, during the late larval stage (0.00028–0.0045
g) and 0.652 during the early juvenile and later stages (0.0045–1230 g). (3) Based on these results, factors controlling the
metabolism-size relationship are discussed. 相似文献
5.
Deficient arylsulfatase A activity causes the neurodegenerative disease metachromatic leukodystrophy. However, some individuals
with deficient enzyme activity appear clinically normal. This “pseudodeficiency” allele commonly found among many reported
populations (frequency ∼ 0.10) is associated with two A→G transitions in cis in the arylsulfatase A gene causing the simultaneous loss of an N-glycosylation and a polyadenylation signal. To understand the evolutionary relationship between such common and tightly linked
mutations, we studied 400 individuals in the African, European, Indian and East Asian populations and found none carrying
the polyadenylation mutation alone. However, the N-glycosylation mutation could occur independently. Its frequency varied from 0.01 in Indians, 0.06 in Europeans, 0.21 in East
Asians to 0.32 in Africans. The frequencies of both mutations occurring together ranged from almost non-existent in the Africans
and East Asians, to 0.075 in the Europeans and 0.125 in the Indians. These frequencies were significantly different among
populations. Haplotype analysis among homozygous pseudodeficiency individuals and eight multi-generation families with six
polymorphic enzymes showed that, of the five haplotypes found in the general population, only one was linked to the double
mutations. Alleles among the four populations with only the N-glycosylation mutation also supported linkage to the same haplotype except in some Europeans whose alleles were discordant.
These results are consistent with the hypothesis that the N-glycosylation mutation may be a recurrent event among the Europeans but first occurred in an ancestral allele before the
emergence of modern Homo sapiens from Africa at ∼100 000–200 000 years ago. Subsequently, the polyadenylation mutation occurred in this ancient allele with
the N-glycosylation mutation, an event that likely took place after the divergence between the European and East Asian lineages.
Received: 23 December 1996 / Accepted: 21 July 1997 相似文献
6.
Brian K. Hall 《Evolution》2012,5(2):184-193
Evolutionary developmental biology (evo–devo) is that part of biology concerned with how changes in embryonic development during single generations relate to the evolutionary changes that occur between generations. Charles Darwin argued for the importance of development (embryology) in understanding evolution. After the discovery in 1900 of Mendel’s research on genetics, however, any relationship between development and evolution was either regarded as unimportant for understanding the process(es) of evolution or as a black box into which it was hard to see. Research over the past two decades has opened that black box, revealing how studies in evo–devo highlight the mechanisms that link genes (the genotype) with structures (the phenotype). This is vitally important because genes do not make structures. Developmental processes make structures using road maps provided by genes, but using many other signals as well—physical forces such as mechanical stimulation, temperature of the environment, and interaction with chemical products produced by other species—often species in entirely different kingdoms as in interactions between bacteria and squid or between leaves and larvae (Greene Science 243:643–666, 1989). Not only do genes not make structures (the phenotype), but new properties and mechanisms emerge during embryonic development: genes are regulated differentially in different cells and places; aggregations of similar cells provide the cellular resources (modules) from which tissues and organs arise; modules and populations of differently differentiated cells interact to set development along particular tracks; and organisms interact with their environment and create their niche in that environment. Such interactions are often termed “epigenetic,” meaning that they direct gene activity using mechanisms that are not encoded in the DNA of the genes. This paper reviews the origins of evo–devo, how the field has changed over the past 30 years, evaluates the recognition of the importance for development and evolution of mechanisms that are not encoded in DNA, and evaluates what the future might bring for evo–devo. Although impossible to know, history tells us that we might expect more of the same; expansion of evo–devo into other areas of biology (ecology, physiology, behavior); absorption of evo–devo by evolution or a unification of biology in which evo–devo plays a major role. 相似文献
7.
A chip for catching, separating, and transporting bio-particles with dielectrophoresis 总被引:1,自引:0,他引:1
Huang JT Wang GC Tseng KM Fang SB 《Journal of industrial microbiology & biotechnology》2008,35(11):1551-1557
This study aims at developing a 3D device for catching, separating, and transporting bio-particles based on dielectrophoresis
(DEP). Target particles can be simultaneously caught and transported using the negative DEP method. In non-uniform electric
fields, the levitation height or complex permittivity of certain particle may be different from that of another and this property
can facilitate separation of particles. We have designed and constructed a 3D device consisting of two layers of electrodes
separated by a channel formed by 50 μm thick photoresist. The electrodes can operate effectively with 10–15 V and 5–7 MHz
to catch all particles in the channel, and can move particles after switching the electric field to 5–15 V and 500–1,000 KHz.
Hence, particles experienced coupling force of two different directional twDEP forces, and tallied with our estimation to
move along the coupling direction. 相似文献
8.
S. C. Makwana 《Primates; journal of primatology》1978,19(3):483-492
The data presented here resulted from about 1,100 observation hours in a nine-month field study of rhesus monkey from January
to October 1976 in the Asarori Forest, Dheradun. Six groups were studied, the group size varied from 6–90 individuals. With
the exception of one group, all were of the bisexual multimale type. The number of adult males per group varied from two to
seven, and of adult females from 4 to 27. The adult sex ratio was male 1 to females 2.2–3.7 (mean 1:2.7). The exceptional
group originally consisted of five juveniles only (3 ♂, 2 ♀); later on an adult male joined the group. Home ranges varied
from 1.3–13.4 km2 and overlapped extensively with another. The area of home range showed straight line relationship with group size. Roosting
sites were not fixed but changed from night to night. The straight line distance between one night to the next varied from
75–2,500 m. Foraging routes per day ranged from 1,050–3,500 m (mean 1,803.3±160.2). There is a significant relationship between
the foraging route (L) and the straight line distance between roosting sites (D). The ratio D/L varies from 0.14–0.87. 相似文献
9.
We have previously computed the structures of three loops, residues 591–596, 654–675 and 742–751, in the ras-p21 protein-binding
domain (residues 568–1044) of the guanine nucleotide-exchange-promoting SOS protein that were crystallographically undefined
when one molecule of ras-p21 (unbound to nucleotide) binds to SOS. Based on our computational results, we synthesized three
peptides corresponding to sequences of each of these three loops and found that all three peptides strongly inhibit ras-p21
signaling. More recently, a new crystal structure of SOS has been determined in which this protein binds to two molecules
of ras-p21, one unbound to GTP and one bound to GTP. In this structure, the 654–675 loop and residues 742–743 and 750–751
are now crystallographically defined. We have superimposed our energy-minimized structure of the ras-binding domain of SOS
bound to one molecule of ras-p21 on the X-ray structure for SOS bound to two molecules of ras-p21. We find that, while the
two structures are superimposable, there are large deviations of the residues 673 and 676 and 741 and 752, flanking the two
loop segments. This suggests that the binding of the extra ras-p21 molecule, which is far from each of the three loops, induces conformational changes
in these domains and further supports their role in signal transduction. In spite of these differences, we have superimposed our computed structures for the loop
residues on those from the more recent X-ray structure. Our structure for the 654–675 segment is an anti-parallel beta-sheet
with a reverse turn at residues 663–665; in the X-ray structure residues 655–662 adopt an alpha-helical conformation; on the
other hand, our computed structure for residues 663–675 superimpose on the X-ray structure for these residues. We further
find that our computed structures for residues 742–743 and 750–751 are superimposable on the X-ray structure for these residues. 相似文献
10.
Different populations suffer from different rates of obesity and type-2 diabetes (T2D). Little is known about the genetic
or adaptive component, if any, that underlies these differences. Given the cultural, geographic, and dietary variation that
accumulated among humans over the last 60,000 years, we examined whether loci identified by genome-wide association studies
for these traits have been subject to recent selection pressures. Using genome-wide SNP data on 938 individuals in 53 populations
from the Human Genome Diversity Panel, we compare population differentiation and haplotype patterns at these loci to the rest
of the genome. Using an “expanding window” approach (100–1,600 kb) for the individual loci as well as the loci as ensembles,
we find a high degree of differentiation for the ensemble of T2D loci. This differentiation is most pronounced for East Asians
and sub-Saharan Africans, suggesting that these groups experienced natural selection at loci associated with T2D. Haplotype
analysis suggests an excess of obesity loci with evidence of recent positive selection among South Asians and Europeans, compared
to sub-Saharan Africans and Native Americans. We also identify individual loci that may have been subjected to natural selection,
such as the T2D locus, HHEX, which displays both elevated differentiation and extended haplotype homozygosity in comparisons
of East Asians with other groups. Our findings suggest that there is an evolutionary genetic basis for population differences
in these traits, and we have identified potential group-specific genetic risk factors. 相似文献
11.
Nitrogen isotopes have been widely used to investigate trophic levels in ecological systems. Isotopic enrichment of 2–5‰ occurs with trophic level increases in food webs. Host–parasite relationships deviate from traditional food webs in that parasites are minimally enriched relative to their hosts. Although this host–parasite enrichment pattern has been shown in multiple systems, few studies have used isotopic relationships to examine other potential symbioses. We examined the relationship between two gut-nematodes and their lizard hosts. One species, Physaloptera retusa, is a documented parasite in the stomach, whereas the relationship of the other species, Parapharyngodon riojensis (pinworms), to the host is putatively commensalistic or mutualistic. Based on the established trophic enrichments, we predicted that, relative to host tissue, parasitic nematodes would be minimally enriched (0–1‰), whereas pinworms, either as commensals or mutualists, would be significantly enriched by 2–5‰. We measured the 15N values of food, digesta, gut tissue, and nematodes of eight lizard species in the family Liolaemidae. Parasitic worms were enriched 1±0.2‰ relative to host tissue, while the average enrichment value for pinworms relative to gut tissue was 6.7±0.2‰. The results support previous findings that isotopic fractionation in a host–parasite system is lower than traditional food webs. Additionally, the larger enrichment of pinworms relative to known parasites suggests that they are not parasitic and may be several trophic levels beyond the host. 相似文献
12.
Stéphane Tirard 《Origins of life and evolution of the biosphere》2010,40(2):215-220
Many theories on origin of life at the end of the XIXth century and the beginning of the XXth, generally use conceptions of
life instead of explicit definitions of life. This paper presents ideas on the origin of life as studied by Buffon (1707–1788),
Lamarck (1744–1829), Darwin (1809–1882), Huxley (1825–1895), Oparin (1894–1980) and Haldane (1892–1964). We show that their
conceptions on the evolution of matter and life reveal their conceptions of life rather than their definitions of life. 相似文献
13.
In this work, the distribution of nine metals in two types of cultivated mushroom had been investigated. For Agaricus bisporus, the biomass was separated into caps and stalks, and for Pleurotus ostreatus, the entire mushrooms were taken for analysis. Electrothermal atomic absorption spectrometry was used for total element determination
in acid digests. For accuracy checking, the certified reference material (NIST 1571, citrus leaves) was analyzed. The results
obtained for the two fungi species were within the ranges of concentration reported previously by other authors. Subcellular
fractionation was accomplished by centrifugation of cell homogenates, which has been suspended in Tris-HCl buffer. In the
first centrifugation (7300g, 4°C, 10 min), cell walls were separated (pellet I), and the second centrifugation (147,000g, 4°C, 60 min) yielded mixed membrane fraction (pellet II) and cytosol (supernatant II). Recoveries of the fractionation procedure
were in the range 70–100% (with the exception of Fe). For all elements studied, the highest relative contributions were found
in cytosol fractions of the fruiting bodies (63–72%, 49–76%, 44–93%, 26–87pc, 55–85%, 50–68%, 41–78%, 39–78%, 54–67% respectively
for Al, Bi, Cd, Cr, Cu, Fe, Mn, Ni, and Pb. Lower contributions were found in cell walls (respectively 22–32%, 24–44%, 6.1–47%,
12–52%, 7.3–37%, 7.9–32%, 19–52%, 20–42%, and 25–38%) and only minute amounts in the mixed membrane fraction (3.0–5.8%, 0.7–7.0%,
0.7–8.3%, 1.0–22%, 7.5–14%, 16–24%, 1.1–19%, and 5.1–7.7%). The results obtained indicate that small water-soluble molecules
were the primary forms of nine elements in two mushroom species studied. On the other hand, the evidence has been provided
on elements binding to larger, water-insoluble molecules contained in the structures of cell wall and membranes. The relative
distribution was both element and fungi dependent. Thus, in P. ostreatus, total element levels were higher than in A. bisporus, with the preference for their accumulation in cytosol. On the contrary, total element content in the latter fungi was lower;
however, a clear tendency toward more efficient element incorporation to the water-insoluble structures was observed (no apparent
differences between stalks and caps). These findings might contribute in a better understanding of the accumulation of metals
in mushrooms. 相似文献
14.
Leptin and leptin receptor have been implicated in processes leading to breast cancer initiation and progression. An A to
G transition mutation in codon 223, in exon 6 of the leptin receptor gene (LEPR) can result in glutamine to arginine substitution
(Gln223Arg). A variety of case–control studies have been published evaluating the association between LEPR Gln223Arg polymorphism and breast cancer. However, published studies have yielded contradictory conclusions. This meta-analysis enrolled
eight studies to estimate the overall risk of LEPR
Gln223Arg polymorphism associated with breast cancer. The pooled ORs were performed for codominant model (Arg/Arg versus Gln/Gln; Arg/Gln
versus Gln/Gln), dominant model (Arg/Arg + Arg/Gln versus Gln/Gln), recessive model (Arg/Arg versus Arg/Gln + Gln/Gln). Overall
significantly elevated breast cancer risk was found for recessive model (OR 1.32, 95% CI 1.03–1.69) and for genotype Arg/Gln
versus Gln/Gln (OR 1.16, 95% CI 1.01–1.34). In the stratified analysis by ethnicity, significantly increased risks were also
found among Africans for genotype Arg/Arg versus Gln/Gln: OR 1.86, 95% CI 1.28–2.71, Arg/Gln versus Gln/Gln: OR 1.48, 95%
CI 1.10–1.99, dominant model: OR 1.60, 95% CI 1.21–2.11 and recessive model: OR 1.48, 95% CI 1.07–2.05; for Asians, Arg/Arg
versus Gln/Gln: OR 6.79, 95% CI 3.42–13.47 and dominant model: OR 2.03, 95% CI 1.42–2.90. However, no significantly increased
risk was found among Europeans for all genetic models. In conclusion, the LEPR 223Arg is a low-penetrant risk for developing breast cancer, especially for black African women. 相似文献
15.
No consensus has been recently reached at the relationship between the α1-antichymotrypsin (ACT) signal peptide −15A/T polymorphism
and Alzheimer’s disease (AD) risk. Thus, our study aimed to better assess this association by performing a meta-analysis,
including 4,212 cases and 4,039 controls from 29 studies. Odds ratios (ORs) with the 95% confidence interval (CI) were used
to assess the strength of relationship between ACT −15A/T polymorphism and AD risk. Overall, a borderline statistically significant
association was detected under recessive model comparison in all subjects (AA vs. AT+TT: OR 1.12, 95% CI 1.01–1.25, P = 0.04). But in subgroup analysis by ethnicity, no significant association was found in Caucasians, Asians, or Africans.
Moreover, after exclusion of one study which affect the heterogeneity, the ACT A allele and AA genotype were statistically
associated with late-onset AD (LOAD) risk (AA vs. TT: OR 1.25, 95% CI 1.06–1.48, P = 0.007, A vs. T: OR 1.12, 95% CI 1.03–1.21, P = 0.008), especially in Caucasians. In conclusion, our study suggests that the common α1-antichymotrypsin signal peptide
−15A/T polymorphism may not be a major risk factor for AD. However, the polymorphism is capable of increasing LOAD risk. 相似文献
16.
Ashutosh Kumar Verma Chandralata Raghukumar Pankaj Verma Yogesh S. Shouche Chandrakant Govind Naik 《Biodegradation》2010,21(2):217-233
Textile dye effluents pose environmental hazards because of color and toxicity. Bioremediation of these has been widely attempted.
However, their widely differing characteristics and high salt contents have required application of different microorganisms
and high dilutions. We report here decolorization and detoxification of two raw textile effluents, with extreme variations
in their pH and dye composition, used at 20–90% concentrations by each of the four marine-derived fungi. Textile effluent
A (TEA) contained an azo dye and had a pH of 8.9 and textile effluent B (TEB) with a pH of 2.5 contained a mixture of eight
reactive dyes. The fungi isolated from mangroves and identified by 18S and ITS sequencing corresponded to two ascomycetes
and two basidiomycetes. Each of these fungi decolorized TEA by 30–60% and TEB by 33–80% used at 20–90% concentrations and
salinity of 15 ppt within 6 days. This was accompanied by two to threefold reduction in toxicity as measured by LC50 values against Artemia larvae and 70–80% reduction in chemical oxygen demand and total phenolics. Mass spectrometric scan
of effluents after fungal treatment revealed degradation of most of the components. The ascomycetes appeared to remove color
primarily by adsorption, whereas laccase played a major role in decolorization by basidiomycetes. A process consisting of
a combination of sorption by fungal biomass of an ascomycete and biodegradation by laccase from a basidiomycete was used in
two separate steps or simultaneously for bioremediation of these two effluents. 相似文献
17.
Erika de Wit Wayne Delport Chimusa E. Rugamika Ayton Meintjes Marlo Möller Paul D. van Helden Cathal Seoighe Eileen G. Hoal 《Human genetics》2010,128(2):145-153
Admixed populations present unique opportunities to discover the genetic factors underlying many multifactorial diseases.
The geographical position and complex history of South Africa has led to the establishment of the unique admixed population
known as the South African Coloured. Not much is known about the genetic make-up of this population, and the historical record
is patchy. We genotyped 959 individuals from the Western Cape area, self-identified as belonging to this population, using
the Affymetrix 500k genotyping platform. This resulted in nearly 75,000 autosomal SNPs that could be compared with populations
represented in the International HapMap Project and the Human Genome Diversity Project. Analysis by means of both the admixture
and linkage models in STRUCTURE revealed that the major ancestral components of this population are predominantly Khoesan
(32–43%), Bantu-speaking Africans (20–36%), European (21–28%) and a smaller Asian contribution (9–11%), depending on the model
used. This is consistent with historical data. While of great historical and genealogical interest, this information is also
essential for future admixture mapping of disease genes in this population. 相似文献
18.
G. B. Gerber R. R. Wick C. R. Watson W. Gössner A. M. Kellerer 《Radiation and environmental biophysics》1999,38(2):75-79
Animal experiments have contributed a great deal to our information on effects and risks arising from exposure to radionuclides.
This applies, in particular, to alpha-emitting radionuclides where information from man is limited to thorotrast, 224Ra and 226Ra. The late C.W. Mays was the first to suggest that animal data in conjunction with epidemiological data could allow estimates
of human risks for radionuclides – predominantly from actinides – where information in man is scarce. The ’International Radiobiology Archives of Long-term Animal Studies’ were created through the combined efforts of European,
American and Japanese scientists and aim to safeguard the large amount of existing data on long-term animal experiments and
make them available for, among others, an improved assessment of risks from alpha-emitting radionuclides. This paper summarizes
the structure of the archives and reviews their present status and future plans. It also demonstrates the extensive information
available in these archives on alpha-emitting radionuclides which is suitable for further analysis. Also, the structure of
the animal archives could – in a slightly modified form – accommodate the epidemiological data available on 224Ra and thorotrast and, thus, facilitate a direct comparison of data from man, dogs and rodents.
Received: 9 January 1999 / Accepted in revised form: 23 March 1999 相似文献
19.
James Woodward 《Biology & philosophy》2010,25(3):287-318
This paper attempts to elucidate three characteristics of causal relationships that are important in biological contexts.
Stability has to do with whether a causal relationship continues to hold under changes in background conditions. Proportionality
has to do with whether changes in the state of the cause “line up” in the right way with changes in the state of the effect
and with whether the cause and effect are characterized in a way that contains irrelevant detail. Specificity is connected
both to David Lewis’ notion of “influence” and also with the extent to which a causal relation approximates to the ideal of
one cause–one effect. Interrelations among these notions and their possible biological significance are also discussed. 相似文献
20.
Inventory, differentiation, and proportional diversity: a consistent terminology for quantifying species diversity 总被引:1,自引:0,他引:1
Almost half a century after Whittaker (Ecol Monogr 30:279–338, 1960) proposed his influential diversity concept, it is time
for a critical reappraisal. Although the terms alpha, beta and gamma diversity introduced by Whittaker have become general textbook knowledge, the concept suffers from several drawbacks. First, alpha
and gamma diversity share the same characteristics and are differentiated only by the scale at which they are applied. However,
as scale is relative––depending on the organism(s) or ecosystems investigated––this is not a meaningful ecological criterion.
Alpha and gamma diversity can instead be grouped together under the term “inventory diversity.” Out of the three levels proposed
by Whittaker, beta diversity is the one which receives the most contradictory comments regarding its usefulness (“key concept”
vs. “abstruse concept”). Obviously beta diversity means different things to different people. Apart from the large variety
of methods used to investigate it, the main reason for this may be different underlying data characteristics. A literature
review reveals that the multitude of measures used to assess beta diversity can be sorted into two conceptually different
groups. The first group directly takes species distinction into account and compares the similarity of sites (similarity indices,
slope of the distance decay relationship, length of the ordination axis, and sum of squares of a species matrix). The second
group relates species richness (or other summary diversity measures) of two (or more) different scales to each other (additive
and multiplicative partitioning). Due to that important distinction, we suggest that beta diversity should be split into two
levels, “differentiation diversity” (first group) and “proportional diversity” (second group). Thus, we propose to use the
terms “inventory diversity” for within-sample diversity, “differentiation diversity” for compositional similarity between
samples, and “proportional diversity” for the comparison of inventory diversity across spatial and temporal scales.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献