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61.
Begging, food provisioning, and nestling competition in great tit broods infested with ectoparasites 总被引:9,自引:5,他引:4
Ectoparasites are a ubiquitous environmental component of breedingbirds, and it has repeatedly been shown that hematoph-agousectoparasites such as fleas and mites reduce the quality andnumber of offspring of bird hosts, thereby lowering the valueof a current brood. Selection acting on the hosts will favorphysiological and behavioral responses that will reduce theparasites' impact. However, the results of the few bird studiesthat addressed the question of whether parasitism leads to ahigher rate of food provisioning are equivocal, and the beggingresponse to infestation has rarely been quantified. A changein begging activity and parental rate of food provisioning couldbe predicted in either direction: parents could reduce theirinvestment in the brood in order to invest more in future broods,or they could increase their investment in order to compensatefor the parasites' effect on the current brood. Since the nestlingsare weakened by the ectoparasites they may beg less, but onthe other hand they may beg more in order to obtain more food.In this study we show experimentally that (1) hen fleas (Ceratophyllusgallinae) reduce the body mass and size of great tit (Parusmajor) nestlings, (2) nestlings of parasitized broods more thandouble their begging rate, (3) the male parents increase thefrequency of feeding trips by over 50%, (4) the females do notadjust feeding rate to the lowered nutritional state of nestlings,and (5) food competition among siblings of parasitized broodsis increased. Ultimately the difference in the parental feedingresponse may be understood as the result of a sex-related differencein the trade-off of i0vesting in current versus future broods. 相似文献
62.
Pigment analysis was performed by means of normal phase HPLC on a number of bacteriochlorophyll a and b containing species of purple bacteria that contain a core antenna only. At least 99% of the bacteriochlorophyll in Rhodobacter sphaeroides R26, Rhodopseudomonas viridis and Thiocapsa pfennigii was esterified with phytol (BChl a
p and BChl b
p, respectively). Rhodospirillum rubrum contained only BChl a esterified with geranyl-geraniol (BChl a
GG). Rhodospirillum sodomense and Rhodopseudomonas marina contained, in addition to BChl a
p, small amounts of BChl a
GG, and presumably also of BChl a esterified with dihydro and tetrahydro geranyl-geraniol (2,10,14-phytatrienol and probably 2,14-phytadienol). In all species bacteriopheophytin (BPhe) esterified with phytol was present. The BChl/BPhe ratio indicated that in these species a constant number of 25 ± 3 antenna BChls is present per reaction centre. This number supports a model in which the core antenna consists of 12 - heterodimers surrounding the reaction centre. Determination of the in vivo extinction coefficient of BChl in the core-reaction centre complex yielded a value of ca. 140 mM–1 cm–1 for BChl a containing species and of 130 mM–1 cm–1 for Rhodopseudomonas viridis.Abbreviations BChl
bacteriochlorophyll
- BPhe
bacteriopheophytin
- GG
geranyl-geraniol
- LHI and LHII
core and peripheral antenna complexes
- P
phytol
- RC
reaction centre
Dedicated to the memory of Professor D.I. Arnon. 相似文献
63.
Stephen W. Ball 《Biology & philosophy》1995,10(2):129-180
Gibbard's theory of rationality is evolutionary in terms of its result as well as its underpinning argument. The result is that judgments about what is rational are analyzed as being similar to judgments of morality — in view of what Darwin suggests concerning the latter. According to the Darwinian theory, moral judgments are based on sentiments which evolve to promote the survival and welfare of human societies. On Gibbard's theory, rationality judgments should be similarly regarded as expressing emotional attachments to behavioral norms which originate and function to coordinate social interaction. Consequently, Gibbard's theory of rationality might be used to illuminate Darwin's theory of morality, and vice versa. Additionally, as argued in the present essay, both can be further elaborated, and defended, by developing related themes in philosophical ethics: viz., connected with Hume and 20th-century emotivists. The main problem is that this general Darwinian approach faces widespread opposition nowadays, not only in ethics but in philosophy of science. The purpose of this essay is to analyze Gibbard's theory, critically and constructively, with emphasis on the pertinent commonalities in Darwin, Hume and the emotivists, while also critically addressing their common enemies. The pervasive methodological orientation is to relate this analysis to (philosophy of) science in general, and biological science in particular. 相似文献
64.
Plain tales from the grasslands: extraction, value and utilization of biomass in Royal BardiaNational Park, Nepal 总被引:1,自引:0,他引:1
Katrina Brown 《Biodiversity and Conservation》1997,6(1):59-74
Royal Bardia National Park in Southern Nepal contains a number of internationally endangered wildlife species, and a mix of habitats, including areas of grassland known as phantas. The conservation and current use of these areas is briefly described, including the extraction of grass from inside the National Park by local people living in adjacent villages. The products collected fulfil a range of human needs, both practical and ceremonial. The study attempts to quantify the annual offtake in both material and monetary terms, and comments on the sustainability of the practice. Alternative sources of roofing materials are apparently outside the scope of poorer households. The use of these materials has particular significance given the initiation of a Parks and People Project to implement a Buffer Zone around the National Park and effectively to link conservation and development needs. 相似文献
65.
土壤呼吸的影响因素及全球尺度下温度的影响 总被引:188,自引:19,他引:169
土壤呼吸是指土壤释放CO2的过程,主要由土壤微生物和根系产生。作为一个复杂的生态学过程,土壤呼吸在受到植被,微生物等生物因素影响的同时,也受到了温度,湿度、pH值等环境因素的作用,并且随着人类影响的增强,人为因素的作用也越来越大。根据已有工作,讨论了影响土壤呼吸的主要影响因素及其相互关系,分析了全球范围内湿润地区森林植被的土壤呼吸与纬度的关系以及土壤呼吸与年均温的关系,得出了全球范围的Q10值为1 相似文献
66.
T. G. Nolen P. M. Johnson C. E. Kicklighter T. Capo 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1995,176(2):239-254
1. | Aplysia californica incorporates toxins and pigments from its red seaweed diet into its body and ink, purportedly as a defense against predation. We tested ink's potential defensive function by assessing the survival of green seaweed-fed (red algal toxin deprived) snails in encounters with a natural predator, the sea anemone Anthopleura xanthogrammica. |
2. | Red seaweed-fed Aplysia secreted copious amounts of ink when ensnared in anemone tentacles. A similar amount of ink applied to inkless (green-fed) snails as they were engulfed by an anemone enhanced their survival [71% survived (ink) vs 7% (seawater control)]. Ink caused anemones to reject whitefish (a familiar food) [50% rejected (ink) vs 10% (seawater control)], triggering gastrovascular eversions, which ejected ink as well as prey from their digestive cavities. Snails with only a passive chemical defense (algal toxins, no ink) escaped less often than snails with only an active chemical defense (ink, no red algal toxins) (20% survived vs 71%) and about as often as red algal toxin deprived snails (20% vs 12%). Snails avoided ink by chemical orientation, thus avoiding potential sites of ongoing predation. |
3. | The survival value of ink and the snail's aversion to it supports ink's proposed anti-predator function. |
67.
Summary This field study was undertaken to determine the effect of inoculation withGlomus mosseae on N2 fixation and P uptake by soybean. The inoculation withGlomus mosseae was achieved using a new type of inoculant, alginate-entrapped (AE) endomycorrhizal fungus. N2 fixation was assessed using the A value method. In P-fertilized plots, inoculation with AEGlomus mosseae increased the harvest index based on dry weight (+20%) and N content of seeds (+17%), the A value (+31%) and %N derived from fixation (+75%). Inoculation with AEGlomus mosseae decreased the coefficient of variation for the A value and for the dry weights of the different plant parts. 相似文献
68.
69.
Monod's equation adequately described aerobic biodegradation rates of benzene and toluene by the microbial population of a sandy aquifer when these compounds were initially present at concentrations lower than 100 mg/l each. Concentrations higher than 100 mg/l were inhibitory, and no benzene or toluene degradation was observed when these compounds were initially present at 250 mg/l each. The Monod coefficients were calculated as k = 8.3 g-benzene/g-cells/day and Ks = 12.2 mg/l for benzene, and k = 9.9 g-toluene/g-cells/day and Ks = 17.4 mg/l for toluene. Specific first-order coefficients would be 0.68 l/mg.day for benzene and 0.57 l.mg.day for toluene. 相似文献
70.
Summary The chemical equilibrium and E value for Zn was calculated in 9 soils of Haryana (India) which represented mainly entisol
and inceptisols. The rate of isotopic exchange between65Zn and native soil Zn was quite rapid and radioactivity reduced to about 0.2 per cent of initial activity after 3 days but
total Zn concentration in soil solution did not decrease. In 5 out of 9 soils equilibrium was established in 2 to 3 days.
In typic ustochrepts having high clay content (3,4) equilibrium was attained in two days. In typic udipsamments (2), typic
camborthids (8) and aquic vertic ustichrepts (9) it took 3 days to set equilibrium. Typic ustochrepts (5) took 5 days for
equilibrium whereas typic ustipssaments (6) and typic camborthids of high O.C. did not attain equilibrium even in 7 days.
This indicated that the chemistry and availability of Zn in soil would depend on soil types.
When ZnE was estimated by applying activity after equilibrium with carrier Zn and by applying activity with carrier Zn before equilibrium
was set, there was no agreement in ZnE in two methods. Increasing ZnE with increasing Zn dose was observed by both methods only in alkaline typic ustochrept (4). In some soils higher E values
than added amounts were observed, whereas, in soil 8 negative E values were obtained. The E values become erratic and are
over estimated where complex reactions take place due to high pH, high O.C. and high complex forming elements. 相似文献