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921.
Carlos Navarro Florentino de Lope Anders Pape Møller 《Behavioral ecology and sociobiology》2007,61(8):1161-1168
Homeobox genes regulate development of digits, and it has been suggested that the ratio of length of second to length of fourth
digit reflects such genetic effects in a sex-specific manner. We show that digit ratios in the sexually dichromatic house
sparrow Passer domesticus differ between sexes, with males having higher ratios than females, and that individuals produce consistent ratios on the
two feet. If Homeobox or other genes had pleiotropic effects on development of digits, behavior, and physiology of males and
females, we would expect secondary sexual characters and immunity to be related to digit ratio in a sex-specific manner. The
size of the visible part of the black badge in February (a secondary sexual character), but not total badge size, was positively
correlated with digit ratios, suggesting that males with more male-like digit ratios had larger visible badges. Because of
sex-specific effects of development on secondary sexual characters and immunity, we predicted sex-specific differences in
immune response to be related to digit ratio. House sparrows with large digit ratios had weaker T cell-mediated immune response
than individuals with small digit ratios, particularly in females, implying that females with more male-like digit ratios
had weak immune responses. These findings are consistent with the hypothesis that early development, as reflected by digit
ratios, and genetics affect the expression of adult characters that are supposedly strongly contributing to fitness. 相似文献
922.
Richard A. Holland 《Behavioral ecology and sociobiology》2007,61(5):653-660
Bats have been extensively studied with regard to their ability to orient, navigate and hunt prey by means of echolocation,
but almost nothing is known about how they orient and navigate in situations such as migration and homing outside the range
of their echolocation system. As volant animals, bats face many of the same problems and challenges as birds. Migrating bats
must relocate summer and winter home ranges over distances as far as 2,000 km. Foraging bats must be able to relocate their
home roost if they range beyond a familiar area, and indeed circumstantial evidence suggests that these animals can home from
more than 600 km. However, an extensive research program on homing and navigation in bats halted in the early 1970s. The field
of bird navigation has advanced greatly since that time and many of the mechanisms that birds are known to use for navigation
were not known or widely accepted at this time. In this paper I discuss what is known about orientation and navigation in
bats and use bird navigation as a model for future research in bat navigation. Technology is advancing such that previous
difficulties in studying orientation in bats in the field can be overcome and so that the mechanisms of navigation in this
highly mobile animal can finally be elucidated. 相似文献
923.
Konstantinos Ganias 《Marine Biology》2008,155(3):293-301
Using previously published histological data on multiple, monthly samples of Sardina pilchardus collected in the central Aegean and Ionian Seas (September 1999–August 2000, and November 2000–February 2001), the Mediterranean
sardine was treated as a case study to investigate the biological characteristics of ephemeral spawning aggregations in multiple-spawning
clupeoids. Actively spawning (Day0) females in the Mediterranean sardine, i.e., the daily class of spawners caught a few hours prior, during, or after the spawning
act, were shown to separate spatially from late (Day1+) spawners and non-spawning females, taking with them a large proportion of conspecific males which were also in advanced
spawning condition and in better somatic condition compared to the remaining population. In addition, information from 28
stocks of multiple-spawning clupeoids from a wide range of geographic locations, belonging to 14 species and 2 families (Engraulidae
and Clupeidae), was reviewed and analyzed pertinent to the formation of ephemeral spawning aggregations. Results from the
latter analysis indicated similar patterns of spatial segregation of Day0 spawners in the reviewed clupeoid stocks as in the Mediterranean Sardine, which strongly suggested that the formation of
ephemeral spawning aggregations is a common behavioral trait among multiple-spawning clupeoids.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
924.
Direct solid sampling Zeeman atomic absorption spectrometric methods were developed and successfully applied to the determination of mercury, cadmium, lead and manganese in aquatic plants. Mercury was determined using a specially designed furnace. The other elements were determined by a third generation spectrometer. In 3-field- and dynamic mode the working range was substantially extended and high amounts of analyte were detectable without laborious dilution of solid samples. The measurements were based on calibrations using certified reference materials of organic origin. No matrix effects were observed under the optimised conditions. Results obtained were in good agreement with the certified values. 相似文献
925.
随着三峡大坝的修建.三峡经济飞速发展.带动了利用三峡库区城镇建设用地的变化。本文以三峡库区21个县市1995—2005年城镇建设用用地的变化量为主要研究对象。结合1995-2005年期间第二产业与第三产业的集中指数与区位商的空间分布变化。采用路径分析建模的方法。奠立了城镇建设用地与固定资产投资、社会商品零售总额、第二产值、第三产值及城镇人口的路径模型.确定了备影响因子对蜮镇建设用地变化的影响程度。其中第二产值对城镇建设用地的变化影响最大.影响力最小的是城镇人口。此项研究进一步验证了路径分析模型在土地利用变化驱动力分析研究中的可行性.同时也为库区城镇建设用地的控制提供了参考。 相似文献
926.
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929.
Gail Krantzberg 《The Environmentalist》2008,28(3):301-305
Some argue that a collective vision for the future of the Laurentian Great Lakes is embodied in the␣Great Lakes Water Quality
Agreement (GLWQA). The GLWQA is a binational agreement, first signed in 1972 by Prime Minister Pierre Trudeau and President
Richard Nixon, wherein the two countries (the Parties) commit to “restore and maintain the chemical, physical and biological
integrity of the waters of the Great Lakes Basin Ecosystem.” Article X of the Agreement states that the Parties shall conduct
a comprehensive review of the operation and effectiveness of this Agreement following every third biennial report of the [International
Joint] Commission (IJC). The IJC’s 12th Biennial Report, released in 2004, triggered this important science, program, and
policy review which commenced May 2006. This essay makes the case for a rigorous review, that explores deliberately the future
scope of the Agreement to protect the world’s largest surface freshwater resource, and calls for innovation in the governance
regime of this binational ecosystem. 相似文献
930.
在我从事大学环境教育、科学研究和管理工作的 23年里,我读过曲格平教授不少文章和著作,也直接听过他多次讲话和报告,使我学到了知识,增长了才干,得到了启迪。这次,读完新近由中国环境科学出版社出版的曲格平教授的《梦想与期待》之后,更令我十分振奋,获益匪浅。 《梦想与期待》收集了曲格平教授自 1997年至 2000年间的讲话、演讲和报告以及答国内外新闻媒体的记者提问。虽然各编章相对独立,但读起来却是一本内容翔实,前后连贯,主题突出和时代感很强的著作。 第一,作者以自己的亲身经历,讴歌了改革开放后中国环境保护… 相似文献