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排序方式: 共有8253条查询结果,搜索用时 15 毫秒
931.
932.
I. Nishiumi Satoshi Yamagishi Hiromi Maekawa Chikashi Shimoda 《Behavioral ecology and sociobiology》1996,39(4):211-217
In many polygynous animals, parents invest more heavily in individual sons than in daughters. However, it is unclear if these
differences in investment are a consequence of sex differences in the demand of offspring related to sexual size dimorphism
or a consequence of parental manipulation. Here, we report on parental food delivery frequency in relation to brood size and
brood sex ratio in a wild population of polygynous great reed warblers Acrocephalus arundinaceus. We used the polymorphic microsatellite loci on the Z chromosome to sex chicks. We found that paternal feeding frequency
(times/h per nest) increased not with brood size, but with the proportion of males in the brood, although the demand per nest
was more closely related to brood size than to brood sex ratio. Additionally, the increase in rate of paternal feeding frequency
in relation to the brood sex ratio was much higher than the increase in rate of nestling food demands. Maternal feeding frequency
was independent of both brood size and brood sex ratio. These results strongly suggest that fathers preferentially invest
in their sons. We propose that parents can afford sex-biased parental care in animals in which food provisioning is enough
for all offspring to survive.
Received: 22 January 1996/Accepted after revision: 30 June 1996 相似文献
933.
Maria Cléa Brito de Figueirêdo Geraldo Stachetti Rodrigues Armando Caldeira-Pires Morsyleide de Freitas Rosa Fernando Antônio Sousa de Aragão Vicente de Paulo Pereira Barbosa Vieira Francisco Suetônio Bastos Mota 《Journal of Cleaner Production》2010,18(14):1376-1385
Environmental vulnerability analysis has been sparsely used in environmental performance evaluation (EPE) of technological innovations. The present paper proposes a methodological approach to carry out vulnerability analysis of watersheds and to integrate this analysis into methods of environmental performance evaluation of agro-industrial innovations. This approach is applied to the Ambitec-Life Cycle method, described in Part 1 (this issue) of this study. The case study of green coconut substrate compared to ripe coconut substrate, also described in Part 1 (this issue), is now presented considering the vulnerability analysis of the watersheds where the life cycle stages of these products occur. The integration of vulnerability analysis in Ambitec-Life Cycle contributes to a better understanding of the environmental aspects of agro-industrial technological innovations with potential to cause significant impacts in watersheds where these innovations are implemented. 相似文献
934.
Cliff I. Davidson Chris T. Hendrickson H. Scott Matthews Michael W. Bridges David T. Allen Cynthia F. Murphy Braden R. Allenby John C. Crittenden Sharon Austin 《Journal of Cleaner Production》2010,18(7):698-701
The field of engineering is changing rapidly as the growing global population puts added demands on the earth's resources: engineering decisions must now account for limitations in materials and energy as well as the need to reduce discharges of wastes. This means educators must revise courses and curricula so engineering graduates are prepared for the new challenges as practicing engineers. The Center for Sustainable Engineering has been established to help faculty members accommodate such changes through workshops and new educational materials, including a free access website with peer-reviewed materials. 相似文献
935.
936.
It has been suggested that shapes of burned areas resulting from fires spreading under uniform fuel and meteorological conditions may be described as ellipses, double ellipses, or ovoids. The adequacy of these shapes (together with simulation outputs) as bases for fire spread models was tested by finding the best fits of each shape to maps of experimental fires and comparing the results with fits given by a rectangle (an unlikely fire shape). Each of the models (ellipse, double ellipse, ovoid, simulation model, and even the rectangle) provided adequate approximations to the fire contours used in the tests. The parameter trends found implied that the fires examined tended to become more nearly elliptical in shape and to have higher eccentricity as they grew. 相似文献
937.
938.
939.
Fesenko S. V. Spiridonov S. I. Sanzharova N. I. Anisimov V. S. Aleksakhin R. M. 《Russian Journal of Ecology》2002,33(3):170-177
A mathematical model was constructed to simulate the processes of 137Cs migration in peat soils and its uptake by vegetation. Model parameters were assessed and the pattern of 137Cs distribution over soil profile was predicted in case of peat soils, which are typical of the Russian regions contaminated after the Chernobyl accident. The ecological half-life of 137Cs in the plant-root soil zone was calculated, and a long-term prognosis of the radionuclide uptake by plants was made. 相似文献
940.