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51.
E. I. Vorobyeva 《Biology Bulletin》2009,36(2):139-147
Transition from sarcopterygians to tetrapods is analyzed based on new paleontological, ontogenetic, and molecular data. It is shown that transformation of skeletal fin elements into the tetrapod limb followed the patterns of divergent, parallel, and mosaic development. Morphogenetic plasticity and autonomy of these processes as well as the same developmental bauplan for the limbs of Urodela and Anura are proposed. Variations observed in these processes are regarded as a result of larval adaptations and heterochronies. The latter excludes recapitulation of successive archetypical states (transformation-development of the fish fin into tetrapod limb). The idea that the digits are a novelty relative to the distal radials of the fin is supported. 相似文献
52.
Microbiological and biotechnological characteristics of intensification of aerobic processing of organic waste have been reviewed, with a view for revealing two types of correlations: (1) between the quality of the composts obtained and the microorganisms involved in composting and (2) between physicochemical parameters and consumer properties of the composts. 相似文献
53.
The mesophilic and psychrotolerant microbiota of the air, soil, water, and bottom sediments of the Kinderlinskaya cave (South
Urals, Russia) and the factors affecting the structure of microbial communities were investigated. The pattern of microbial
distribution in soils was shown to depend on both the configuration of the cave and the level of recreational load. The lowest
numbers of bacteria and micromycetes were found in the poorly visited, difficult-to-access sites. Coliform bacteria were revealed
in all soil and sediment samples and in some water samples. Micromycetes belonged to 19 genera, with Geomyces pannorum as the dominant species. Air movement was shown to be the main factor affecting the density of the aerial microbiota. 相似文献
54.
We studied postural reactions evoked by vibrational stimulation of the anterior tibial and posterior neck muscles under three
different conditions of visual control (in a darkened room): (i) upon standing with the eyes open, EO, with perception of
a stationary 2D image of the visual environment on the screen, (ii) under conditions of perception of a 3D virtual visual
environment, VVE, and (iii) upon standing with the eyes closed, EC. Vibrational stimulation of both muscle groups evoked forward
inclinations of the body; average values of the latter under control conditions (EC) were close to each other. The VVE mimicking
a real visual environment possessed two planes, a mobile foreground one, whose shifts were programmed in such a manner that
they correlated with oscillations of the body, and a stable background one. The tested subjects were asked to use the latter
as a visual reference. Under VVE conditions, the amplitude of postural reactions depended on the feedback coefficient between
the body movements and shifts of the VVE foreground and the direction of this feedback (its synphase or antiphase, sph or
aph, mode). Postural responses at the feedback sph direction became greater with increase in the feedback coefficient (i.e.,
with increases in the magnitude of shifts of the VVE foreground) and reached values typical of standing under EC conditions.
In the case of the aph type of feedback, the responses changed insignificantly. If the lowest feedback coefficient, 1.0, was
used, the postural responses tended to decrease, as compared with those under EO conditions. The difference between the values
observed at the sph and aph types of feedback with similar coefficients was manifested more intensely in the case of stimulation
of the neck muscles. This fact shows that postural reactions triggered by afferent signals from the neck muscles depend more
considerably on the ongoing visual afferentation. 相似文献
55.
Brett M. Bennett 《Journal of the history of biology》2011,44(1):125-145
Scholars studying the globalization of Australian trees have previously emphasized the rapid natural propagation of Australian
trees outside of their native habitats, believing their success to be a reversal of “ecological imperialism” from the “new
world” to the “old world.” This article argues that the expansion of Australian trees should not be viewed as a biological
phenomenon, but as the result of a long-term attempt by powerful states and state-sponsored scientists to select and breed
Australian species that could grow in a variety of climates and ecological conditions. Five non-biological factors largely
determined the success of these attempts to grow Australian trees: the abundance or paucity of natural forests, state power,
the amount of scientific research directed to planting Australian trees, the cost of labor, and the ability to utilize hardwood
timbers and bark. This paper compares the use of Australian trees in Australia, India, and South Africa to demonstrate that
biology was not the determining factor in the long-term success of many Australian genera and species. 相似文献
56.
Physiological and biomechanical effects of aerobic exercise varying in intensity were studied on the basis of the subjects’ perceived exertion. It was demonstrated that exercise regulated with the use of a 50–100 rating scale was characterized by reliably stable heart-rate and respiratory reactions and biomechanical responses. The relative working heart rate (HR) expressed in percent of the individual HRmax was found to be closely correlated with the values on the 50–100 scale within a wide range during exercise with constant or increasing perceived exertion. 相似文献
57.
Role of Thidiazuron (TDZ) in inducing adventitious organogenesis in Pongamia was studied. TDZ at different concentrations (0, 0.45, 2.27, 4.54, 6.71, 9.08, 11.35, 13.12 and 22.71 μM) were used for induction
of caulogenic bud formation in deembryonated cotyledon explants. Each cotyledon was cut into three segments and identified
as proximal, middle and distal. Duration of TDZ exposure, influence of the segment and orientation of the explant were studied.
TDZ at 11.35 μM concentration was optimum for the induction of shoots and rapid elongation. Shoots induced at higher concentration
elongated after several passages in growth regulator free medium, thereby extending the period of differentiation. Exposure
of the explant for 20 days yielded more number of buds than 10 days. Proximal segment of the cotyledon was more responsive.
Contact of abaxial surface in the medium was more effective and generated more buds than the adaxial side. Buds differentiated
and elongated on transfer to MS basal medium for 8–12 passages of 15 days each. Rooting and elongation of shoots was achieved
in charcoal supplemented half-strength MS medium. Rooted plantlets survived on transfer to sand soil mixture. The plants were
hardened and transferred to green house. This is the first report on in vitro regeneration of Pongamia pinnata via adventitious organogenesis using TDZ. This protocol may find application in studies in genetic transformation, isolation
of somaclonal variants and in induction of mutants. It also provides a system to study the inhibitory role of TDZ on shoot
differentiation. 相似文献
58.
59.
60.
The article describes the effects of channelization on selected water quality parameters and benthic macroinvertebrate assemblages
in four Big Black River (Mississippi, USA) tributaries crossing the Natchez Trace Parkway [U.S. National Park Service (NPS)].
Two of the streams were unchannelized (Little Bywy Creek and McCurtain Creek), and two were channelized (Big Bywy Creek and
Middle Bywy Creek). Lignite mining occurs in the headwaters of Little Bywy Creek and Middle Bywy Creek. During this 3-year
study, benthic macroinvertebrates were collected monthly from all four streams using Hester-Dendy Multiple plate samplers,
and enumerated taxonomically and functionally. Hypotheses were tested using analyses of variance. Relationships were determined
using multivariate analyses. Relative abundances of mayflies (Ephemeroptera), stoneflies (Plecoptera), caddisflies (Trichoptera)
and aquatic beetles (Coleoptera) were associated with moderate to high conductivity, alkalinity, pH, and dissolved oxygen.
Hellgrammites (Megaloptera), midges, blackflies, and mosquitoes (Diptera), crayfish (Crustacea: Decapoda) and leeches (Annelida:
Hirudinea) were associated with lower values for these parameters. These patterns reflected seasonal rather than spatial variation
(i.e., among the streams). Invertebrate assemblage composition was similar among the four streams with respect to functional
groups. Invertebrate relative abundances in the two channelized streams were approximately half those of the unchannelized
streams. Macroinvertebrate species richness was greater in unchannelized streams. Environmental indices categorized all four
streams as having fair to good condition.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献