共查询到19条相似文献，搜索用时 46 毫秒
1.
2.
3.
4.
衣原体能引起人类或动物的多种疾病,临床上多以隐性、持续感染的形式表现,原因与其为了对付宿主免疫系统等方面所形成的不利环境而发展的一系列策略不无关系。本文就衣原体生存策略的新进展作一综述。 相似文献
5.
地下啮齿动物栖息环境及其生存策略研究 总被引：1，自引：0，他引：1
地下啮齿动物一般生活在黑暗、低氧、高二氧化碳、高湿的环境中,这种独特的栖息环境以及地下啮齿动物与之相适应的形态、行为等特征已成为生态学研究的热点之一。由于地下啮齿动物长期营地下生活,增加了对其栖息环境和生存策略的研究难度,相关的文献报道较少。为全面了解当前地下啮齿动物栖息环境方面的研究进展,本文综述了国内外有关地下啮齿动物的生存环境和生存策略方面的研究,旨在为今后探索地下啮齿动物生存环境及其对环境的适应能力、控制地下啮齿动物危害及保护草地生物多样性提供参考依据。 相似文献
6.
胜利大坂是新疆天山的一座高大山峰,海拔高度4010米。从乌鲁木齐市出发,沿216国道西南行,穿过砾石戈壁,途经永丰小镇后不久进入山区,溯乌鲁木齐河上行1.5—2.0小时光景即可抵达,全程约145公里左右。这里的植物长的都非常低矮,犹如植物世界里的一个“小人国”,其中有贴地或匍匐生长的植物群落,好似一片片花色相间的绿色地毯,岩石上色彩斑斓的多种地衣,更如同一副副美妙的画卷。天山胜利大坂附近的高山植物及其所形成的植被,体态各异、奇特和科学内涵丰富,无疑是科普教育和生态旅游的好去处。 相似文献
7.
请看下面这道题:有两个不同物种的种群(甲和乙),对环境的要求(生态位)相近。若这两个种群生活在同一自然区域,通过长期的进化发展,一般会出现如下图A、B、C3种情况中的一种。请用文字表述图中所反映的两个种群的进化趋势。 相似文献
8.
在生物界中 ,生物种类繁多 ,形态各异 ,形式多样。从简单到复杂 ,从低级到高级 ,不一而足。在这丰富多彩的生物界中 ,有一类单细胞真核生物 ,它们形体微小 ,构造简单 ,没有组织、器官和系统的分化 ,但具备生物的全部功能——生长、运动、繁殖、变异、遗传、新陈代谢、应激和适应等。在复杂和多变的环境中 ,多细胞生物因其具有高度分化的组织、器官 ,可有效地应付环境中的各种变化而生存。那么单细胞生物如何生存呢 ?下面介绍几种单细胞原生动物的生存策略。1 细胞质外的保护层——表膜多细胞生物的组织细胞一般仅有 1层质膜 ,除植物细胞有… 相似文献
9.
10.
11.
Charles R. Brown Mary Bomberger Brown 《Evolution; international journal of organic evolution》1998,52(5):1461-1475
Extreme climatic disturbances provide excellent opportunities to study natural selection in wild populations because they may cause measurable directional shifts in character traits. Insectivorous cliff swallows (Petrochelidon pyrrhonota) in the northern Great Plains must often endure periods of cold weather in late spring that reduce food availability, and if cold spells last four or more days, mortality due to starvation may result. We analyzed morphological shifts associated with viability selection, and how patterns of bilateral symmetry were affected by survival selection, during a four-day period of cold weather in 1992 and a six-day period in 1996 in southwestern Nebraska. Birds that died during the cold were compared to those still alive when the severe weather ended. The event in 1992 killed relatively few birds, but the cold spell in 1996 killed thousands of cliff swallows and reduced their population by about 53%. Climatological records suggest that mortality events comparable to that of 1996 have occurred in only one other year since 1875. Larger birds were favored in the 1996 event. Selection was more intense in 1996 than in 1992 because of more stressful conditions in 1996. Directional selection gradient analysis showed that measures of skeletal body size (tarsus length, culmen width and length) and wing length were targets of selection in 1996. Survivors had lower wing and outer tail asymmetry, and wing and tail asymmetry were targets of selection in both events. Mortality patterns did not differ by sex, but older birds suffered heavier mortality; morphological traits generally did not vary with age. Nonsurvivors were not in poorer apparent condition prior to the weather event than survivors, suggesting that selection acted directly on morphology independent of condition. Selection on body size in cliff swallows was more intense than in studies of body size evolution in other bird species. Larger swallows were probably favored in cold weather due to the thermal advantages of large size and the ability to store more fat. Swallows with low asymmetry were favored probably because low asymmetry in wing and tail made foraging more efficient and less costly, conferring survival advantages during cold weather. This population of cliff swallows may have undergone relatively recent body size evolution. 相似文献
12.
Slow life histories are characterized by high adult survival and few offspring, which are thought to allow increased investment per offspring to increase juvenile survival. Consistent with this pattern, south temperate zone birds are commonly longer‐lived and have fewer young than north temperate zone species. However, comparative analyses of juvenile survival, including during the first few weeks of the post‐fledging period when most juvenile mortality occurs, are largely lacking. We combined our measurements of fledgling survival for eight passerines in South Africa with estimates from published studies of 57 north and south temperate zone songbird species to test three predictions: (1) fledgling survival increases with length of development time in the nest; (2) fledgling survival increases with adult survival and reduced brood size controlled for development time; and (3) south temperate zone species, with their higher adult survival and smaller brood sizes, exhibit higher fledgling survival than north temperate zone species controlled for development time. We found that fledgling survival was higher among south temperate zone species and generally increased with development time and adult survival within and between latitudinal regions. Clutch size did not explain additional variation, but was confounded with adult survival. Given the importance of age‐specific mortality to life history evolution, understanding the causes of these geographical patterns of mortality is important. 相似文献
13.
北京东灵山地区辽东栎(Quercus liaotungensis)种群生活史特征与空间分布 总被引：3，自引：0，他引：3
种群生活史特征和空间分布格局对于分析种群演替动态规律、判定种群分布规律和预测种群演化过程及变化趋势均具有重要的理论和现实意义.本文从静态生命表、年龄结构、存活曲线三个方面分析了东灵山地区辽东栎种群的生活史特征.结果表明:物种生物学因素是影响辽东栎种群生存力最主要因素,辽东栎种群静态生命表中生命期望值逐渐降低反映出种群生存力下降的趋势.空间分布格局分析表明辽东栎种群各个径级的个体都属于聚集分布.辽东栎实生苗和萌生苗共存是辽东栎种群适应环境压力和与环境协同进化的结果,表明自然状态下辽东栎种群具有较高的稳定性.由于辽东栎种群的这种较强的稳定性和适应能力,随着辽东栎种群发育整个群落将趋于进展演替,最终形成稳定和充分利用环境资源的顶极群落结构. 相似文献
14.
1. Prior studies suggest that both the mean and variation of worker size predict the performance of bumble bee colonies. The ‘variation hypothesis’ posits that colony performance increases with variation of worker body size due to more efficient division of labour within colonies. The ‘mean size hypothesis’ posits that colony performance increases with mean bumble bee size, as each individual's efficiency tends to increase with body size. 2. The present study tested these non‐mutually exclusive hypotheses by establishing 62 Bombus impatiens Cresson (Hymenoptera, Apidae) nest boxes in 32 semi‐natural savanna fragments within large‐scale experimental landscapes in South Carolina (U.S.A.). 3. Based on measurements of > 24 000 individuals and on colony growth over ～7 weeks, our results support the mean size hypothesis, not the variation hypothesis. 相似文献
15.
R. S. Wotton 《Hydrobiologia》1982,96(3):243-251
The life histories of Simulium noelleri Fried. and S. truncatum Ldstr. were studied at a lake-outlet site in Finland. A detailed study was made of the second summer generation of both species
and this consisted of a single, synchronized cohort in S. noelleri, and overlapped cohorts in S. truncatum. Larvae of the two species also show differences in their habitat preference: those of S. noelleri predominate on the sluice which marks the beginning of the river, and S. truncatum larvae just downstream from the sluice. In winter, the latter site was dominated by immature individuals of two other species,
S. erythrocephalum de Geer and S. equinum L., and these were found downstream from the two ‘lake-outlet’ species during the summer.
Adult females of S. noelleri are able to mature a first batch of eggs without taking a blood meal but those of S. truncatum need to feed on blood before eggs can be fully developed. The consequences of these different reproductive strategies on
the ecology of individuals of the two species is discussed. 相似文献
16.
Abstract. Parasites can influence the population dynamics of their hosts by affecting life-history strategies and behavior. The hematophageous mite Riccardoella limacum lives in the lung cavity of terrestrial gastropods. We used correlational and experimental approaches to investigate the influence of parasite infection on the behavior and life-history traits of the simultaneously hermaphroditic land snail Arianta arbustorum , a common host of R. limacum. Naturally infected individuals of A. arbustorum , collected in the wild, showed a decreased activity compared with uninfected snails. The reproductive output, expressed as the number of eggs deposited in a reproductive season, was reduced in mite-infected hosts. However, the hatching success of the eggs laid by parasitized snails was slightly higher than that of uninfected individuals. We also examined winter survival in 361 adults of A. arbustorum collected from four natural populations. The prevalence of mite infection ranged from 44.8% to 70.1% in three populations (snails in the fourth population were not infected). Winter survival was reduced in infected snails in two out of three populations. Furthermore, experimentally infected snails from an uninfected population showed a reduced winter survival compared with control snails. Our results indicate that parasite pressure imposed by members of R. limacum may influence life history in A. arbustorum. 相似文献
17.
SUMMARY AN account is given of some aspects of the reproductive ecology and larval development of Lubeo umbrutus which is of great importance in the Eastern Cape due to its abundance in rivers and dams. The sex ratio was found to be approximately 1:1 and females probably have a longer life span than males. Spawning takes place from October to January. Males become sexually mature at a length of 14 cm and females at a length of 20 cm. A spawning site is described. There is a curvilinear relationship between length and fecundity with the average fecundity increasing from 11 000 in fishes with a length of 20 cm to 48 000 in fishes with a length of 32 cm. Larval development from hatching to an age of 12 days is described. 相似文献
18.
J.-F. Rubin 《Journal of fish biology》1995,46(4):603-622
A new method is described to estimate the survival of salmonids in streams from fertilization of the eggs to the emergence of the fry. The method is compared to other techniques generally used to estimate the egg-to-fry survival: fry traps, excavation of redds, construction of artificial redds and laboratory experiments. Especially designed boxes filled with substratum and freshly fertilized eggs are buried in the stream bed. Survival is determined at three different embryological development stages: eyed stage, hatching and emergence. Boxes are planted inside the stream bed using a special injector, so that substratum alterations are minimal around the boxes. This method was tested successfully in two different studies, one in Switzerland on the brown trout, the other one in Sweden on the sea trout. 相似文献
19.
综述了生活史性状、生活史对策、权衡、适合度及进化种群统计学等动物生活史进化领域的进展。权衡是生活史性状之间相互联系的纽带,分为生理权衡与进化权衡。适合度是相对的,与个体所处的特定环境条件有关,性状进化与适合度之间关系紧密。适合度是生活史进化理论研究的焦点。探讨动物生活史对策的理论很多,影响最大的是MacArthur和Wilson提出的r对策及K对策理论。随年龄的增长,动物存活率及繁殖率逐步下降的过程,称为衰老;解释衰老的进化理论主要有突变-选择平衡假设和多效对抗假设。进化种群统计学将种群统计学应用于生活史进化研究,为探讨表型适合度的进化提供了有效的手段。将进化种群统计学、数量遗传学及特定种系效应理论进行整合,建立完整的动物生活史进化综合理论体系,是当代此领域的最大挑战。 相似文献