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1.
A cladistic approach to the phylogeny of the “Bryophytes”   总被引:1,自引:0,他引:1  
The importance of a cladistic approach in reconstructing the phylogeny of bryophytes is discussed and illustrated by an analysis of the major groups of bryophytes with respect to the tracheophytes and the green algae. The cladistic analysis, using 51 characters taken from the literature, gives the following tentative results: (1) the embryophytes as a whole are monophyletic; (2) the bryophytes (sensu lato) are paraphyletic; (3) the mosses share a more recent common ancestor with the tracheophytes than do the liverworts or hornworts; (4) the hornworts appear to share a more recent common ancestor with the moss-tracheophyte lineage than with the liverworts; however, the existence of several homoplasies makes this placement more problematical; (5) the origin of alternation of generations in the embryophytes, based on out-group comparison with their oogamous, haplontic, algal sister groups, was by progressive elaboration of the primitively epiphytic sporophyte generation; and (6) the presence of vascular tissue (xylem and phloem) can best be interpreted as a synapomorphy of the moss-tracheophyte clade, and tracheids (xylem with ornamented walls) as a synapomorphy of the tracheophytes; therefore, the prevailing designation of “vascular plants” for the tracheophytes alone is inaccurate.  相似文献   

2.
Jiliang Hang 《Steroids》2010,75(12):879-883
A convenient synthesis of sidechain-modified phytosterols is achieved via a temporary masking of the stigmasterol 5,6-alkene as an epoxide. Following performance of the desired modification, the alkene is regenerated through a mild deoxygenation. The approach is applied to the syntheses of β-sitosterol and campesterol acetate, and suggests a facile route to the (Z)-isomers of Δ22-23 phytosterols.  相似文献   

3.
《朊病毒》2013,7(2):89-93
Deposits of amyloid fibrils characterize a diverse group of human diseases that includes Alzheimer’s disease, Creutzfeldt-Jakob disease and type II diabetes. Amyloid fibrils formed from different polypeptides contain a common cross-β spine. Nevertheless, amyloid fibrils formed from the same polypeptide can occur in a range of structurally different morphologies. The heterogeneity of amyloid fibrils reflects different types of polymorphism: (i) variations in the protofilament number, (ii) variations in the protofilament arrangement and (iii) different polypeptide conformations. Amyloid fibril polymorphism implies that fibril formation can lead, for the same polypeptide sequence, to many different patterns of inter- or intra-residue interactions. This property differs significantly from native, monomeric protein folding reactions that produce, for one protein sequence, only one ordered conformation and only one set of inter-residue interactions.  相似文献   

4.
Robert Paine 《Ethnos》2013,78(1-4):161-172
The Raw and the Cooked. Claude Levi‐Strauss. Jonathan Cape 1970. 387 pp., ill., bibl. Price £3.5.0.

Folktales of Israel. Ed. by Dov Noy with the assistance of Dan Ben Amos. Transi, by Gene Baharav. The University of Chicago Press. Folktales of the World. Chicago 1963. 221 S. $ 4.00.

Politics of Social Research. An inquiry into the ethics and responsibilities of social scientists. Ralph L. Beals. Aldine Publishing Company. Chicago 1969. 228 pp.

African Stone Sculpture. Philip Allison. Percy Lund, Humphries &; Co., Ltd. London 1968. 71 pp. 99 pls. 3 maps. Price 56 s.

The Elementary Structures of Kinship. (Les Structures élémentaires de la Parenté). Claude Lévy‐Strauss. Rev. ed. translated from the French by James Harle Bell, John Richard von Sturmer and Rodney Needham, Editor. Beacon Press, Boston; Eyre &; Spottiswoode Ltd., London. 1969. 541 pp., 87 figs. Price $ 15.00.

Contes sous la Croix du Sud. Giselle de Goustine. (Les littératures populaires de toutes les nations. N.S., T. XIII). Editions G.‐P. Maisonneuve et Larose, Paris 1967. 208 pp.

La divination malgache par le sikidy. Raymond Decary avec la collaboration de Marcelle Urbain‐Faublée. Publications du centre Universitaire des Langues Orientales Vivantes, 6e série, vol. IX. Paul Geuthner, Paris 1970. 111 pp.

Über Lebensraum und Lebensformen des Frühsemiten. Joseph Henninger. Arbeitsgemeinschaft für Forschung des Landes Nordrhein‐Westfalen. Geisteswissenschaften, Heft G 151. Westdeutscher Verlag. Köln und Opladen 1968. 61 Seiten. Kart. DM 6.60.

Indianer von gestern, heute und morgen. Beobachtungen zum Kulturwandel in den Anden Boliviens. Hermann Trimborn. Kulturgeschichtliche Forschungen; 12. Band. Albert Limbach Verlag, Braunschweig 1968. 96 S., 104 Abb., 1 Karte. Preis DM 38:—.

Der Wandel ökonomischer Rollen bei den westlichen Dan in Liberia. Eberhard Fischer. Studien zur Kulturkunde, Band XXI. Franz Steiner Verlag, Wiesbaden. Wiesbaden 1967. 481 S. 4 Taf. 7 Abb. DM 66:—.

An Anthropological Bibliography of South Asia. Together with a Directory of Anthropological Field Research. Vol. III. 1960–64. Compiled by

Elizabeth von Fürer‐Haimendorf and Helen Kanitkar. Le Monde d'Outre‐Mer Passé et Présent, Quatrième Série. Bibliographies VIII. Editions Mounton &; Cie, Paris 1970. 562 pp. Price 193 F.

Man‐apes or Ape‐men? The Story of Discoveries in Africa. Sir Wilfrid E. Le Gros Clark. Holt, Rinehart and Winston, Inc., New York 1967. 150 pp., 33 fig., bibliography, index. Price $3.95.  相似文献   

5.
Deposits of amyloid fibrils characterize a diverse group of human diseases that includes Alzheimer disease, Creutzfeldt-Jakob disease and type II diabetes. Amyloid fibrils formed from different polypeptides contain a common cross-β spine. Nevertheless, amyloid fibrils formed from the same polypeptide can occur in a range of structurally different morphologies. The heterogeneity of amyloid fibrils reflects different types of polymorphism: (1) variations in the protofilament number, (2) variations in the protofilament arrangement and (3) different polypeptide conformations. Amyloid fibril polymorphism implies that fibril formation can lead, for the same polypeptide sequence, to many different patterns of inter- or intra-residue interactions. This property differs significantly from native, monomeric protein folding reactions that produce, for one protein sequence, only one ordered conformation and only one set of inter-residue interactions.Key words: Alzheimer disease, aggregation, neurodegeneration, prion, protein folding  相似文献   

6.
7.
The contributions of “new” carbon coming from plants with the C4-type of photosynthesis (maize) and “old” carbon from soil organic matter (SOM) formed under C3 vegetation as carbon sources for microorganisms was determined. Soil samples were taken from the plots of field experiments on Chernozem and Phaeozem. The values of δ13C were determined in evolved CO2, SOM, total microbial biomass (Cmic), and phospholipid fatty acids (PLFA), assuming that the PLFA markers for certain taxonomic groups of microorganisms enriched in C4 carbon indicated a more significant role of these microorganisms in the transformation of root exudates and plant residues. Carbon pools were arranged in the following order by the degree of their enrichment with “new” C: SOM < Cmic < CO2. Consequently, the “new” carbon proved to be a more preferable substrate for microbial growth than the “old” one. The share of C4 in the markers varied from 18 to 60% (on average 38%) in Phaeozem and from 15 to 40% in Chernozem (on average 28%). The groups of microorganisms in Phaeozem were arranged in the following order by the degree of their enrichment with “new” carbon: protozoa < saprotrophic fungi < actinomycetes < gram-positive bacteria < gramnegative bacteria < mycorrhizal fungi. In Chernozem, the contribution of C4 to the carbon composition of PLFA did not differ significantly for various groups of microorganisms. The C4 content within the PLFA markers of fungi and gram-negative bacteria did not demonstrate any crucial contribution of these groups of organisms to the transformation of “new” C. The long-term C3–C4 transition probably results in formation of a broad range of carbon pools similar in their C4 content but different in resistance to mineralization; therefore, gram-positive bacteria could assimilate C4 from resistant C pools. The low content of “new” carbon in the PLFA markers of fungi may be explained by a considerable portion of dormant forms.  相似文献   

8.
A combined ITS and β-tubulin gene phylogeny has revealed new species of Hypocrella and Aschersonia related to the type species Hypocrella discoidea from natural forest in Thailand. As a result, Hypocrella calendulina and Hypocrella luteola are named as new species with Aschersonia sensu stricto anamorphs for specimens previously identified as Hypocrella discoidea sensu Petch. Hypocrella siamensis and Aschersonia minutispora are described as new species, both exhibiting brown stromata, with the former producing whole ascospores.  相似文献   

9.
This study quantifies long-term landscape changes in the Hawaiian archipelago relating to dispersal, speciation and extinction. Accounting for volcano growth, subsidence and erosion, we modelled the elevations of islands at time intervals of 0.5 Myr for the last 32 Myr; we also assessed the variation in the spacing of volcanoes during this period. The size, spacing and total number of volcanic islands have varied greatly over time, with the current landscape of large, closely spaced islands preceded by a period with smaller, more distantly spaced islands. Considering associated changes in rates of dispersal and speciation, much of the present species pool is probably the result of recent colonization from outside the archipelago and divergence within contemporary islands, with limited dispersal from older islands. This view is in accordance with abundant phylogenetic studies of Hawaiian organisms that estimate the timing of colonization and divergence within the archipelago. Twelve out of 15 multi-species lineages have diverged within the lifetime of the current high islands (last 5 Myr). Three of these, and an additional seven (mostly single-species) lineages, have colonized the archipelago within this period. The timing of colonization of other lineages remains uncertain.  相似文献   

10.
11.
Stephen T. Hasiotis 《Ichnos》2013,20(4):313-314
Gastroliths are usually described as being highly polished, but no technique has actually been used to measure the amount of polish. The use of profilometer and laser light‐scattering measurements on gastroliths, suspected gastroliths, and fluvial clasts are applications of technology new to geology and paleontology. These techniques permit rapid and nondestructive tests and can be used to quantify the surface polish of materials having irregular surfaces. A pilot study of these three populations indicates that suspected and bona fide gastroliths are generally much more highly polished than fluvial clasts.  相似文献   

12.
Among Scarabaeoidea, pollen feeding occurs in two major lineages, pleurostict Scarabaeidae and Glaphyridae. Here we infer for the first time the phylogeny of the scarabaeoid lineage Glaphyridae (Coleoptera) based on molecular data using partial gene sequences for 28S rRNA, cytochrome oxidase I (cox1) and 16S rRNA (rrnL) for 41 species. Based on the resulting tree topology, we inferred the timing of the origin of pollination and of their coevolution with different flower host taxa, with particular focus on the prominent red-coloured ‘poppy guild’ flowers. All genera of Glaphyridae that were sampled with multiple species were recovered as monophyletic. According to this analysis, the origin of Glaphyridae was around 140 Ma, while crown group divergence was dated to have occurred c. 112 Ma. Pollen feeding originated in Glaphyridae only once and much later than in other important pollinator groups, between 97 and 67 Ma. According to the reconstruction of ancestral feeding traits, Asteraceae (Cicharioidae) were the first hosts of Glaphyridae. Presumably, a further adaptive radiation was triggered by feeding on and pollination of red flowers (poppy guild) which arose at a later stage. It occurred for the first time between 30 and 40 Ma, whereby the clades that use red Ranunculaceae (Pygopleurus spp.) are older than clades using exclusively red Papaveraceae (Eulasia spp.) (25–30 Ma). The rather young age of red Ranunculaceae would imply that Pygopleurus species only subsequently used red Ranunculus species as flower hosts, and that a broad parallel host shift probably from red Papaver spp. to red Ranunculus asiaticus has occurred rather recently.  相似文献   

13.
Photographs are a ubiquitous feature of Aboriginal life in Northeastern Australia, with images of relatives being prominently displayed in most Aboriginal houses. This display of photographs is tied to a form of distributed personhood that draws on photographs to create a sense of social immediacy in the absence of close kin. This sense of immediacy also occurs in relation to photographs of the dead, giving these images a particular force for Aboriginal viewers. But further consideration of this force of photographic images suggests that they should be treated neither as things nor as aspects of persons, despite their seeming ability to manifest agency in Aboriginal life-worlds.  相似文献   

14.

Background  

The need to depict a phylogeny, or some other kind of abstract tree, is very frequently experienced by researchers from a broad range of biological and computational disciplines. Thousands of papers and talks include phylogeny figures, and often during everyday work, one would like to quickly get a graphical display of, e.g., the phylogenetic relationship between a set of sequences as calculated by an alignment program such as ClustalW or the phylogenetic package Phylip. A wealth of software tools capable of tree drawing exists; most are comprehensive packages that also perform various types of analysis, and hence they are available only for download and installing. Some online tools exist, too.  相似文献   

15.
Summary The sequences of the A chains of the eye lens protein-crystallin from seventeen mammalian species were compared. They showed a generally slow rate of evolution, but with marked variations in different lineages. Most substitutions have occurred in the C-terminal part of the chain, which probably forms part of the surface of the-crystallin aggregate. The ancestral sequence method of Dayhoff revealed interesting indications about the phylogenetic relationships between the eleven mammalian orders that were represented by the investigated species. Most evident was the divergence of marsupial and placental orders. A notable resemblance between the hyrax and elephant sequences was observed, setting them apart from the ungulates, including whale. Primates, rodents, lagomorphs, insectivores and tupaiids seem to derive from a common stem group. These phylogenetic inferences are discussed in relation to current palaeontological and taxonomical opinions, and compared to evidence from other protein sequence data.  相似文献   

16.
17.
In the present essay, I first recall the genealogical concept of classification settled by Charles Darwin in the Origin of Species. Darwin tightly linked what we now call phylogeny and development. He often insisted to take into account embryonic and larval characters, most often using as examples his favourite animals, the cirripedes. Then I discuss remaining problems, and also perspectives, to address the link between phylogeny and development in the modern terms of molecular and cladistic phylogenetics and of molecular and genetic developmental biology.  相似文献   

18.
Abstract

M.A. Hjortso and J.W. Roos, Eds. Marcel Dekker, New York, 1994; hardbound pp. xi + 273, $135.00  相似文献   

19.
We summarize the ethnographic literature illustrating that “abnormal birth” circumstances and “ill omens” operate as cues to terminate parental investment. A review of the medical literature provides evidence to support our assertion that ill omens serve as markers of biological conditions that will threaten the survival of infants. Daly and Wilson (1984) tested the prediction that children of demonstrably poor phenotypic quality will be common victims of infanticide. We take this hypothesis one stage further and argue that some children will be poor vehicles for parental investment yet are not of demonstrably poor quality at birth. We conclude that when people dispose of infants due to “superstitious beliefs” they are pursuing an adaptive strategy in eliminating infants who are poor vehicles for parental investment. Catherine Hill lectures in biological anthropology/human sciences at Durham University’s University College, Stockton. She trained in biological anthropology at University College, London. Her current research interests include human and nonhuman primate socioecology and human resource ecology and development issues. Helen Ball lectures in biological anthropology/human sciences at Durham University’s University College, Stockton. She trained in biological anthropology at the University of Massachusetts at Amherst. Her current research interests include nonhuman primate behavior and socioecology, reproductive biology, and evolutionary issues.  相似文献   

20.
As interest in ethnics and their entrepreneurial activities has grown in recent years, sociologists have come to emphasize the importance of ethnic social structures as the source of actions propelling business growth. In a sign of convergence with the ‘new economic sociology’, recent literature suggests that embeddedness in ethnic networks and communities leads to cooperative, if not conformist, behaviour among ethnic economic actors. This article looks at the ‘other side’ of embeddedness, through a case‐study of African‐American, Caribbean, Korean and white construction contractors in New York City. I argue that, in construction, the embeddedness of economic behaviour in ongoing social relations among a myriad of social actors impedes access to outsiders. Embeddedness contributes to the liabilities of newness that all neophytes encounter, breeding a preference for established players with track records. However, the convergence of economic and ethnic ties has a further baneful effect, since outsiders also fall outside those networks that define the industrial community. While African‐American, Caribbean and Korean outsiders all experience these barriers in similar ways, they differ in the adaptive strategies that they have pursued. African Americans appear to be most disadvantaged, in part because they have been the most exposed to the social closure that results from the mobilization of white ethnics’ social capital. By contrast, Caribbeans and Koreans entered the labour market in societies where racial domination played little or no role in labour market outcomes ‐ a considerable asset since construction skills are transferable from one society to another. The Koreans appear to be the most embedded in ethnic networks, through which they secure jobs and skilled labour, though class factors play a role here as well and even the Koreans must reach out beyond the ethnic community for a clientele. By contrast, ethnic solidarity operates less powerfully among the black contractors, who are tied to a community where intra‐ethnic diversity and internal competition have grown as a result of immigration. In the absence of an ethnic market, black'entrepreneurs turn to the state, whose requirements and dependence on union labour expose black builders to risks from which their Korean counterparts are sheltered.  相似文献   

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