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11.
甘肃东乡几种早中新世哺乳动物化石 总被引:14,自引:3,他引:11
本文记述了在甘肃东乡椒子沟发现的几种早中新世哺乳动物化石:Gomphotherium sp、Dzungariotheriura orgosense、Rhinocerotidae gen. indet.和Paraentelodon macrognathus sp. nov.,着重讨论了全北区猪齿兽类的系统关系。根据化石的性质判断,东乡椒子沟化石点的地质时代应与欧洲Burdigalian早期,亦即MN_3相当或稍早。笔者将原定为上新世临夏组的第一、二岩性段划出,命名为椒子沟组,其时代为早中新世。 相似文献
12.
昆都仑鱼(Kuntulunia)的新材料及其系统位置的讨论 总被引:2,自引:2,他引:0
本文根据对宁夏六盘山群马东山组的长鳍昆都仑鱼(Kuntulunia longipterus, Liu, Ma et Liu 1982)的新材料的研究,对其形态特征做了一些补充和订正。在此基础上,笔者支持刘宪亭等人将昆都仑鱼归入华夏鱼科(Huashiidae)及华夏鱼科归入骨舌鱼类的观点。并且认为华夏鱼类代表了一新的亚目——华夏鱼亚目(Huashioidei subordo. nov.)。 相似文献
13.
Julian J. Dodson 《Environmental Biology of Fishes》1988,23(3):161-182
Synopsis Fish migration may be viewed as the product of two processes; the selection and tracking of optimal environmental conditions
through time and space, and the use of predictive information about environmental structure to bias movements towards a goal.
The establishment and maintenance of directional bias is based on the interaction of experience and instinct. The preoccupation
of much fish orientation research with innate fixed patterns of behavior on one hand and hydrodynamics on the other has led
us to underestimate the possibility that orientation is a flexible process relying on developmental sequences, calibration
of the motor-sensory interaction based on experience and the learning of environmental pattern. Evidence illustrating how
experience and learning may influence the direction of movement and how the goal is recognized is presented according to two
general categories: (a) imprinting and early experience and (b), spatial learning, including the social transmission of migratory
routes and directions. In the first category, the olfactory hypothesis of salmon homing is briefly reviewed and new data presented
describing olfactory imprinting in Atlantic salmon,Salmo salar. In the second category, evidence is presented demonstrating the modifiability of sun-compass orientation and the ability
of some fish species to learn the spatial distribution of landmarks. The role of social transmission in the migration of coral
reef fishes is reviewed. The possible role of these learning phenomena in the formation of familiar area maps, route-based
and location-based navigation and the critical distance factor is considered. The relationship between life history and the
nature of learning in migratory orientation is discussed 相似文献
14.
M. R. Naidu P. Singh B. S. Dahiya 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1988,75(3):514-517
Summary Selection in the F3 generation for seed yield, fruiting branches/plant, effective pods/plant, and seed index (100-seed weight) was carried out in two chickpea crosses. Sixty F5 lines (15 lines/selection criterion) along with check variety were evaluated for seed yield in three distinct environments. The effects of selection criteria on yield stability was examined using linear regression approach and genotype-grouping technique. There were no differences between selection criteria for linear yield responses of F5 lines to different environments. Within all four selection criteria the lines showed similar linear responses. The non-linear component was relatively higher for lines selected for effective pods and seed index than lines selected for yield and fruiting branches. On the basis of mean yield and coefficient of variation across environments, the seed index was the least effective selection criterion for developing high yielding and stable lines. When the results of stability parameters and genotype-grouping technique were considered together, selection for yield and fruiting branches was highly effective for isolating stable and high yielding lines. 相似文献
15.
A gentle method for the isolation of nuclei from developing silk glands ofBombyx mori has been standardized. The nuclei, whether isolated or directly visualizedin situ within the silk glands, exhibit complex morphology. The nuclei occupy almost the entire volume of the gigantic silk gland
cells. Although the isolated nuclei still retain their ramified morphology, being polyploid they are fragile and often become
fragmented. The histone and low-salt-extractable proteins from nuclei isolated from the middle and posterior silk glands on
different days of the fourth and fifth instars of larval development have been analysed. The histones did not show any stage-
or tissue-specific variations whereas the low-salt-extractable proteins showed some developmental stage specific variation.
Using the antibody raised against one such protein, its absence in the early stage of development has been confirmed by Western
blotting techniques. This developmental stage specific protein may be functionally linked to some activities responsible for
boosting up the production of silk or silk-related proteins during the fifth instar of larval development. 相似文献
16.
Background processes at the population level during succession in grasslands on sand 总被引:1,自引:0,他引:1
Two population characteristics, reproductive allocation (RA) and the intensity of photosynthesis, were investigated in the successional stages of the sandy grassland communities of the Great Hungarian Plain. Most of the species studied changed their allocational response as succession advanced. Compound path schemes, as casual models, were constructed and analysed for describing intra-individual effects (influence of assimilating organs and root mass of the plant sampled) as well as the phytosociological effects on RA. In pioneer stages, the high values of path coefficients show that the effect of assimilating organs is responsible for the variability of RA. It is also shown that annuals and perennials exhibit different behaviour as to the regulation of RA. It seems that-in terms of path analysis-the reproduction of annuals is influenced by internal factors only. In case of perennials, an external (namely phytosociological) regulation was also observed. It is suggested that successional stages play a role in regulating the photosynthetic intensity of both the dominant species and the whole plant assemblage.Abbreviations RA =
Reproductive Allocation 相似文献
17.
R. R. Hill Jr. F. L. Kolb H. G. Marshall 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1991,81(1):79-82
Summary Parameters estimated from a Gardner-Eberhart analysis of the F2 generation of a six-parent diallel in oats (Avena sativa L.) were used to compare methods for predicting the performance of F3 row plots. The prediction methods were: (1) individual F2 plant performance (F2I), (2) parent average plus F2 plot deviations (PF2), (3) parent average plus weighted F2 plot deviations (PF2P), (4) best linear unbiased prediction (BLUP) of parent average plus F2 plot deviations (BPF2), and (5) BLUP plus weighted F2 deviations (BF2). The F2 single-plant traits used for prediction were biological yield to predict F3 biological yield, whole plant and primary tiller grain yield for prediction of F3 grain yield, and whole plant and primary tiller harvest index (HI) to predict F3 HI. Prediction methods were evaluated by correlations between predicted and observed F3 performance. Prediction methods and traits for which correlations were greater than for F2I included: BF2 for biological yield, PF2, PF2P and BF2 for whole plant grain yield, PF2, BPF2, and BF2 for primary tiller grain yield. None had a correlation significantly greater than F2I for either measure of HI, where heritability was large. PF2 is the recommended method for traits with low heritability because of its simplicity and because it had the largest or nearly the largest correlation for each of the yield traits. F2I is the recommended method for traits with larger heritability.Contribution No. 8821 of the U.S. Regional Pasture Research LaboratoryDeceased 相似文献
18.
19.
记真盔甲鱼类两新属——兼论真盔甲鱼类系统发育关系 总被引:11,自引:11,他引:0
本文记述了早泥盆世真盔甲鱼类两新属:憨鱼属(Nochelaspis)和翼角鱼属(Pterogonaspis).真盔甲鱼类是盔甲鱼类的一个单系类群,现有七属十二种,文中运用分支系统学原理对其系统发育关系进行了初步探讨. 相似文献
20.
酸性水和投加铝、钙对鲢鱼早期发育和鳃超微结构的影响 总被引:4,自引:1,他引:3
在实验室条件下,研究了酸性水和投加铝、钙对鲢鱼胚胎孵化和鱼苗存活以及幼鱼鳃超微结构的影响。pH4.0引起所有胚胎在24小时内死亡,暴露于pH4.5—6.0的胚胎孵化率和暴露于pH4.0—6.0的5—15日龄鱼苗存活率随pH值上升而增高。投加0.5mg Al~(3+)/L使在酸性pH暴露条件下的胚胎孵化率和鱼苗存活率进一步降低。投加3.0mg Ca~(2+)/L可显著提高暴露于pH4.5和5.0的胚胎孵化率;投加2.0mg Ca~(2+)/L可在一定程度上提高暴露于pH4.5和5.0的鱼苗存活率。幼苗经pH4.5暴露8小时后出现严重的鳃超微结构损害;投加1.0mg Al~(3+)/L使鳃结构损害加剧;投加5.0mg Ca~(2+)/L可明显缓解酸性水对鳃的损害。 相似文献