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Morphological Complexity (morphological + complexity)
Selected AbstractsCURRENT VARIABILITY SHAPES MORPHOLOGICAL COMPLEXITY IN COLONIAL STREAM DIATOMSJOURNAL OF PHYCOLOGY, Issue 2001Article first published online: 24 SEP 200 Passy, S. I.1,2 & Freehafer, D.2 1Department of Biology, Rensselaer Polytechnic Institute, Troy, NY 12180; 2US Geological Survey, 425 Jordan Rd., Troy, NY 12180-8349 USA On August 27, 1999 diatoms were sampled, and current velocity was measured at 81 locations on a regular square sampling grid in an unshaded, cobble-bottom reach of White Creek, NY. The grid had an extent of 16 m2, interval, the distance between neighboring sampling points, of 0.5 m, and grain size, the size of the elementary sampling unit, of 0.01 m2. Six of the seven dominant benthic diatoms were colonial forms, including Diatoma vulgaris, Fragilaria capucina, F. crotonensis, Gomphoneis minuta, Melosira varians, and Synedra ulna. Their morphology and distribution were investigated from the perspective of fractal geometry and stream ecology, respectively. Fractal dimension of diatom colonies, indicative of their shape complexity, ranged from 1.06 to 1.54, demonstrating vast morphological variation from simple geometric shapes to complex outlines. The relative abundance of the six diatoms was regressed against current regime, which ranged from 0.03 to 0.66 m, s -1. All regression models were significant at P < 0.05 and explained between 55% and 94% of the variation in diatom distribution. The diatom niche breadth, i.e. the amount of environmental variability a species can tolerate, was defined from these models and showed substantial variation, from 5 to 14. The regression model of fractal dimension against niche breadth was significant and explained 76% of colonial shape variation, revealing a strong relationship between diatom colonial complexity and habitat variability. This finding suggests that environmental variability could create highly complex colonial morphologies in benthic diatoms as an evo-lutionary strategy for survival in unpredictable environments. [source] Influences of habitat complexity on the diversity and abundance of epiphytic invertebrates on plantsFRESHWATER BIOLOGY, Issue 4 2003Hiromi Taniguchi SUMMARY 1. The compound influence of habitat complexity and patch size on stream invertebrate assemblages associated with submerged macrophytes was investigated through field sampling of two natural macrophyte species with contrasting leaf morphologies (complex, Ranunculus yezoensis; simple, Sparganium emersum) and an experiment with two artificial plants with different levels of morphological complexity. 2. The artificial plant experiment was designed to separate the effects of habitat area (patch size) and habitat complexity, thus enabling a more rigorous assessment of complexity per se than in previous studies where only a single patch size was used. Simple and complex artificial plants were established with five different patch sizes corresponding to the range found in natural plants. 3. Invertebrates occurred on both complex and simple forms of natural and artificial plants at similar abundances with dipterans and ephemeropterans being predominant. Taxon richness was higher on structurally complex Ranunculus than on simple Sparganium and was similarly higher on the complex artificial plant than on the simple one, over the entire range of habitat patch sizes. Thus, architectural complexity affected the taxon richness of epiphytic invertebrates, independently of habitat scale. 4. On the natural plants there was no difference in the abundance (both number of individuals and biomass) of invertebrates between simple and complex forms, while on artificial plants more invertebrates occurred on complex than on simple forms. The amount of particulate organic matter, >225 ,m (POM) and chlorophyll a showed mixed patterns on natural and artificial plants, suggesting that the availability of these resources is not an overriding proximate factor controlling invertebrate abundance on plants. The difficulty of extrapolating from experimental results involving use of artificial plants is discussed, especially when considering the relationship between habitat structure and the occurrence of epiphytic invertebrates on natural plants. [source] Structure, function and evolution of the gas exchangers: comparative perspectivesJOURNAL OF ANATOMY, Issue 4 2002J. N. Maina Abstract Over the evolutionary continuum, animals have faced similar fundamental challenges of acquiring molecular oxygen for aerobic metabolism. Under limitations and constraints imposed by factors such as phylogeny, behaviour, body size and environment, they have responded differently in founding optimal respiratory structures. A quintessence of the aphorism that ,necessity is the mother of invention', gas exchangers have been inaugurated through stiff cost,benefit analyses that have evoked transaction of trade-offs and compromises. Cogent structural,functional correlations occur in constructions of gas exchangers: within and between taxa, morphological complexity and respiratory efficiency increase with metabolic capacities and oxygen needs. Highly active, small endotherms have relatively better-refined gas exchangers compared with large, inactive ectotherms. Respiratory structures have developed from the plain cell membrane of the primeval prokaryotic unicells to complex multifunctional ones of the modern Metazoa. Regarding the respiratory medium used to extract oxygen from, animal life has had only two choices , water or air , within the biological range of temperature and pressure the only naturally occurring respirable fluids. In rarer cases, certain animals have adapted to using both media. Gills (evaginated gas exchangers) are the primordial respiratory organs: they are the archetypal water breathing organs. Lungs (invaginated gas exchangers) are the model air breathing organs. Bimodal (transitional) breathers occupy the water,air interface. Presentation and exposure of external (water/air) and internal (haemolymph/blood) respiratory media, features determined by geometric arrangement of the conduits, are important features for gas exchange efficiency: counter-current, cross-current, uniform pool and infinite pool designs have variably developed. [source] Confocal microscopy of the light organ crypts in juvenile Euprymna scolopes reveals their morphological complexity and dynamic function in symbiosisJOURNAL OF MORPHOLOGY, Issue 5 2006Laura K. Sycuro Abstract In the hours to days following hatching, the Hawaiian bobtail squid, Euprymna scolopes, obtains its light-emitting symbiont, Vibrio fischeri, from the surrounding environment and propagates the bacteria in the epithelial crypts of a specialized light organ. Three-dimensional analyses using confocal microscopy revealed that each of the three crypts on either side of the juvenile light organ is composed of four morphological regions. Progressing from the lateral pore to the medial blind end of each crypt, the regions consist of 1) a duct, 2) an antechamber, 3) a bottleneck, and 4) a deep region. Only the deep region houses a persistent bacterial population, whereas the duct, antechamber, and bottleneck serve as conduits through which the bacteria enter during initial colonization and exit during diel venting, a behavior in which ,90% of the symbionts are expelled each dawn. Our data suggest that, like the duct, the antechamber and bottleneck may function to promote and maintain the specificity of the symbiosis. Pronounced structural and functional differences among the deep regions of the three crypts, along with previously reported characterizations of embryogenesis, suggest a continued developmental progression in the first few days after hatching. Taken together, the results of this study reveal a high degree of complexity in the morphology of the crypts, as well as in the extent to which the three crypts and their constituent regions differ in function during the early stages of the symbiosis. J. Morphol. © 2006 Wiley-Liss, Inc. [source] Patterns of Development in Spanish L2 Pragmatic Acquisition: An Analysis of Novice Learners' Production of DirectivesMODERN LANGUAGE JOURNAL, Issue 4 2006LYNN PEARSON This article investigates from an acquisitional approach the development of pragmatic competence by novice learners of second language (L2) Spanish. Specifically, it examines the acquisition of various strategies (e.g., head acts, use of softeners, formality marking, and hearer-oriented directives) to realize Spanish directives. A quantitative and qualitative analysis of the data detected patterns in the learners' directive production. The analysis considered factors such as instruction, L2 grammatical competence, and the influence of the first language (L1) to illustrate the patterns of development of L2 pragmatics at lower proficiency levels. The results show (a) verb forms with increased morphological complexity replaced lower level directive strategies, possibly as a result of the expansion of L2 grammatical competence; (b) pragmatic competence seems to precede grammatical competence; and (c) the L1 pragmatic system appears to play a role in interpreting and processing new L2 data for use in production. [source] 3,4-Diethyl-2,5-dihydro-1H -pyrrole-2,5-dioneACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2007Frédérique Brégier In the crystal structure of the title compound, C8H11NO2, three distinct molecules are present in the asymmetric unit. The molecules are organized in two different hydrogen-bonded tapes, which form a complex layered structure. A structural comparison with the crystal structures of related maleimide derivatives unravels a stepwise evolution of morphological complexity with increasing molecular complexity for this class of compounds. [source] | ||||||||||