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We first review the suite of general problems mammals confrontduring their social development, and then focus on the specificproblem of how group-living mammals acquire their social rank.In particular, we examine maternal rank "inheritance" (MRI)in those mammals for which maternal rank is the primary determinantof female rank. This occurs in many primates and in spottedhyenas. Young primates and spotted hyenas usually attain theiradult status in two stages: they first attain ranks correlatedwith those of their mothers in peer interactions, and subsequentlychallenge and outrank older conspecifics subordinate to theirmothers. Observational learning may be necessary, but is notsufficient, for MRI. In some primates, but not hyenas, youngstersappear to learn their ranks from direct aggression against themby higher-ranking adults. Third-party support appears to promoteMRI in all species examined: the probability and style of maternalinterventions on behalf of infants often vary with rank, andboth kin and nonkin frequently form coalitions that may assistjuveniles during rank reversals.  相似文献   
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Fifteen primer pairs were designed for 14 polymorphic microsatellite loci, which were isolated and characterized from genomic libraries of Rhynchosporium secalis. Conditions for multiplexing and simultaneous genotyping of up to eight loci in a single run are described. The number of alleles per polymorphic locus ranged from two to 13 in populations from Switzerland and Australia. Genotypic diversity ranged from 61.5 to 66.7. Gene diversity ranged from 0.08 to 0.89 for individual polymorphic loci, with averages of 0.54 and 0.62 for the populations from Switzerland and Australia, respectively. Variable levels of polymorphism make these ideal markers for population genetic analyses.  相似文献   
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LIGHT ABSORPTION BY PLANTS AND ITS IMPLICATIONS FOR PHOTOSYNTHESIS   总被引:10,自引:0,他引:10  
The preceding account has attempted to examine the interactions between light absorption and photosynthesis, with reference to both unicellular and multicellular terrestrial and aquatic plants. There are, however, some notable plant groups to which no direct reference has been made, e.g. mosses, liverworts and lichens. Although many have similar optical properties to terrestrial vascular plants (Gates, 1980) and apparently similar photosynthetic responses (see Green & Snelgar, 1982; Kershaw, 1984) they may possess subtle, as yet unknown differences. For instance, the lichen thallus has a high surface reflectance although the transmittance is virtually zero (Gates, 1980; Osborne, unpublished results). It is envisaged, however, that differences in optical properties between species will reflect differences in degree not kind. Although not all variation in photosynthesis is due to differences in light absorption a number of accounts suggest that this is a contributing factor. Variations in leaf absorptance have been found to account for most of the variation in leaf photosynthesis at low Jis (see Ehleringer & Björkman, 1978a; Osborne & Garrett, 1983). There is, however, little direct experimental evidence on light absorption and photosynthesis in either microalgal species or aquatic macrophytes. We also do not know over what range of incident photon flux densities photosynthesis is determined largely by changes in light absorption. Plants growing under natural conditions also experience large diurnal and seasonal fluctuations in Ji, unlike species grown under laboratory conditions. The occurrence of transitory peaks in Ji tends to overshadow the fact that the average Ji is often lower than the J1 required to saturate photosynthesis, i.e. 1500–2000 μmol m-2 s-1, depending on the growth treatment. Using the data of Monteith (1977) and I W m2= 5 μmol m-2 s-1, and with photosynthetically active radiation 50% of total solar radiation, the daily mean value for Britain is approximately 450 μmol m-2 s-1, with a maximum in June of 1000μmol m-2 s-1 and a minimum during the winter of 75 μmol m-2 s-1. Such values could be even lower on shaded understory leaves and considerably lower for aquatic species. Based on average values of net photosynthesis for a terrestrial plant leaf, light saturation would only be expected in June while for most of the year the average values would lie largely on the light-limited portion of the photosynthesis light response curve. Although the daily average values in tropical climates may be higher during the winter months, they are remarkably similar throughout the world for the respective summers in the northern and southern hemispheres, because the increased daylength at high latitudes compensates for the lower Jis. The expected lower dark respiration rates during the winter may also partially offset the effects of a lower light level. There is therefore a trade-off between high Jis for a short period of time against a lower Ji for a longer period of time. We might expect different photosynthetic responses to these two very different conditions. Importantly, a low Ji with a long daylength may enable a plant to photosynthesize at or near its maximum photon efficiency for most of the day. Although the response of the plant to fluctuations in Ji is complicated because it is affected by the previous environmental conditions, this may indicate that light absorption has a much greater significance under natural conditions, particularly for perennial species. The bias in many laboratories towards research on terrestrial vascular plants also tends to ignore the fact that a number of multicellular and unicellular aquatic species survive in very low light environments. Furthermore, the direct extrapolation of photosynthetic responses from measurements on single leaves to those of whole plants is clearly erroneous. Although this is obvious, many physiological ecologists have attributed all manner of things to the photosynthetic responses of ‘primary’ leaves. Most researchers have ignored problems associated with composite plant tissues and internal light gradients. Clearly caution is required in interpreting the photosynthesis light-response curve of multicellular tissues based on biochemical features alone. Also, the importance of cell structure on light absorption and photosynthesis has generally been ignored and attributed solely to the effects of structural features on CO2 diffusion. In doing so the work of two or three generations of plant physiologists has been ignored. Haberlandt (1914) at the turn of the century probably first implicated the role of cell structure in leaf optics, and Heath (1970) stressed that in order to completely understand the role of light in photosynthesis we need to know the flux incident on the chloroplast itself. Even this suggestion may need modification because of the capacity of the internal chloroplast membranes for scattering light. It is worth emphasizing the importance of light gradients within tissues and their role in regulating photosynthesis, particularly at light saturation. Measurements of light gradients are fraught with problems because of experimental difficulties and the majority (few) are based on reflectance and transmittance measurements. Seyfried & Fukshansky (1983) have shown that light incident on the lower surface of a Cucurbita cotyledon produced a larger light gradient than light incident from above, indicating the importance of the spatial arrangement of the tissues with respect to the light source. Also, light incident on the lower surface of leaves of Picea sitchensis was less ‘effective’ in photosynthesis than light from above (Leverenz & Jarvis, 1979). Clearly, two tissues could have the same gross absorptance but different photosynthetic rates because of differences in the internal light environment. Fisher & Fisher (1983) have recently found asymmetries in the light distribution within leaves, which they related to asymmetries in photosynthetic products due to differences in solar elevation. Such modifications in light distribution could be important for a number of solar-tracking species. Changes in light absorption are brought about by a whole gamut of physiological, morphological and behavioural responses which serve to optimize the amount of light absorbed. Perhaps the simplest way of regulating the amount of light absorbed is by restricting growth either to particular times of the year or to conditions when the light climate is favourable. We are still largely ignorant of many details of these modifications. In particular, differences in tissue structure such as the size and number of vacuoles or the effects of organelles on the scattering component of the internal light environment of photosynthetic tissues are not understood. A better understanding of the interaction of light with plants in aquatic systems is also required. It is unfortunate that light-absorptance measurements are not routinely made in photosynthetic studies, and this is quite clearly a neglected area of study. That these measurements are not made is even more surprising, since techniques have been available for over sixty years (Ulbricht, 1920). Absorptance measurements are of particular importance in the photosynthetic adaptation of microalgae, where only a small proportion of the incident photon flux density is absorbed. For multicellular species more detailed information is required on internal light gradients and their variability. Light-absorptance measurements are also important in any study relating kinetic data on CO2 fixation to in vivo photosynthesis, especially when there are large variations in the morphology and structure of the photosynthetic organ.  相似文献   
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Cells of Tetrahymena pyriformis syngen 1 grown at 30 C after conjugation achieve sexual maturity more quickly than do cells grown at 19 C, whether time is measured in numbers of cell divisions or in terms of absolute time. This result is achieved regardless of the temperature at which conjugation and nuclear reorganization occur. These observations differ from those of other workers investigating Paramecium, and suggest that the long term “chronometer” is more tightly coupled to cell division in Paramecium multimicronucleatum and Paramecium caudatum than in Tetrahymena pyriformis.  相似文献   
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Abstract. 1. Adult staphylinid beetles Thinopinus pictus LeC. are noct turnal predators of sand beach amphipods, Orchestoidea califomiana (Brandt). I made continuous observations of Thinopinus near the drift patches on which amphipods feed.
2. Thinopinus alternated between active and ambush foraging modes.
3. Thinopinus had greater attack rates and captured smaller amphipods while in active foraging mode.
4. Thinopinus attacked 0.147 amphipods/min, and captured 9.1% of the amphipods attacked. The attack rate on amphipods increased with the proportion of time spent by Thinopinus in active mode.
5. Thinopinus remained longer near types of drift patches which were more attractive to amphipods.  相似文献   
9.
Ochromonas danica, a freshwater, planktonic chrysophyte, is capable of sensing the light conditions of its environment. This biflagellate alga has a swelling near the base of the short flagellum and a chloroplastidic stigma in close association with it. A procedure is described for the isolation of this three dimensional flagellar swelling, the presumed photoreceptor. In contrast to an earlier method developed for the isolation of the paraflagellar swelling from Euglena gracilis, the protocol reported here for Ochromonas results in higher yields that should facilitate future biochemical investigations and could open avenues of investigation for the isolation and purification of the presumptive receptor protein. To verify the hypothesis that a rhodopsin-like protein might be present in this alga, we applied a standard extraction procedure successfully used in the identification of retinal. We here report the purification and identification of all-trans retinal in Ochromonas cells by column chromatography, HPLC and GC-MS. Since retinal is the chromophore of rhodopsin-like proteins, this finding may suggest that in these unicellular algae, too, a rhodopsin-like protein could be the photoreceptor pigment.  相似文献   
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Sodium selenite promotes the growth of bracken fern root callusgrowth over a narrow, low range of concentrations, while higherconcentrations are strongly inhibitory. Pteridium aquilinum, bracken fern, sodium selenite, selenium, callus  相似文献   
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