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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Inference of genetic relationship

Mobbs, Deena Catherine January 1993 (has links)
No description available.
22

The growth and behaviour of soil amoebae in a sterile liquid medium

Harrison, David January 1958 (has links)
No description available.
23

Studies of the terrestrial protozoa of the maritime Antarctic

Smith, Humphrey G. January 1973 (has links)
No description available.
24

Structure and function of extensible cuticle in Rhodnius prolixus Stal

Hillerton, John Eric January 1976 (has links)
No description available.
25

Biochemical polymorphisms in Drosophila populations

Malpica, Jose Maria January 1976 (has links)
No description available.
26

The role of Nocardia spp. symbiotic in Rhodnius prolixus (Triatomidae: Hemiptera)

Hill, Pierre January 1975 (has links)
No description available.
27

Studies on the hypopus forms of members of the Acarina

Wallace, David January 1952 (has links)
No description available.
28

Thermal evolution of body size in Drosophila melanogaster

Azevedo, Ricardo Bruno Rebelo de January 1997 (has links)
The objective of this research was to investigate the causes and consequences of thermal evolution of body size in <I>Drosophila melanogaster. </I>This was done empirically by the integrated study of lines collected along latitudinal gradient and population that were undergoing long-term evolution at different temperatures in the laboratory. All experiments were conducted in the laboratory using controlled conditions of temperature and larval density. I examined 20 populations collected along a north-south transect in Australia (17°-43°S) and found that wing size increased with latitude. The genetic cline in wing size was mostly based on variation in cell number (82%). These findings contradicted previous results on thermal selection in the laboratory, where the divergence in wing size was achieved almost entirely by changes in cell size. In another experiment, 6 geographic lines were reared at 5 temperatures spanning the entire viability range for the species. Wing size, cell size and cell number all decreased with increasing development temperature. Cell size determined most of the plasticity in wing size (˜75%). Wing size increased with latitude across the reaction norm, mostly due to variation in cell number (87%), which repeated the pattern observed at a single temperature. Although there was significant variation among populations in phenotypic plasticity of the wing traits, a latitudinal trend in this variation was only detected for cell size; variation in plasticity of wing size among populations was attributable to both cellular components. The results of these experiments suggest that thermal evolution acted on body size itself, since cell number is the basis of additive genetic variation for body size within populations at a single temperature. In the experiments outlined above, it was also found that the size of the wing, relative to the size of the thorax, and the relative length of the wing both decreased in response to high selection and developmental temperatures.
29

Bird speciation in the Gulf of Guinea

Pinheiro De Melo, Martim Ferreira Pinto January 2006 (has links)
The Gulf of Guinea island system, West Africa, constitutes a spectacular centre of bird endemism, with 33 species unique to the region. It comprises three oceanic islands (Annobón, São Tome, Principe), one land-bridge island (Bioko) and one ecological island (Mount Cameroon), all part of the Cameroon line of volcanoes. This thesis used genetic, morphological and behavioural data from finches, whiteeyes, thrushes and kingfishers to investigate: i) the importance of isolation for the speciation process; ii) the applicability of the current 'ecological model' of speciation, which was developed in parapatric and sympatric situations, to allopatric situations, and iii) the link between character divergence at the population level and the evolution of reproductive isolation. Molecular phylogenies revealed that previous systematic assessments based on phenotypic characters were often incorrect. High levels of phenotypic differentiation of island taxa are not related to time since origin and can evolve within very short periods. For example, Speirops (Zosteropidae) and Neospiza (Fringillidae) are well within the genera Zosterops and Serinus respectively. 'Aberrant' characters did not constitute evidence for shared ancestry, e.g. the "genus" Speirops proved not to be monophyletic. The two Gulf of Guinea endemic kingfishers Alcedo spp. are island populations of the mainland Malachite kingfisher A. cristata, rather than being distinct island species. In contrast, molecular evidence in combination with phenotypic data strongly supported the elevation of the thrush population from Principe Turdus olivaceofuscus xanthorhynchus to species status. Molecular data also revealed a possible case of cryptic speciation within the Principe white-eye Zosterops ficedulinus. The high number of endemic bird species in the Gulf of Guinea islands was the result of recent speciation events rather than the accumulation of relict species extinct on the mainland. Therefore, the Gulf of Guinea constitutes a very important centre of bird speciation in Africa. Because the oceanic islands are surrounded by one of the richest centres of biodiversity in the world they were colonised by several bird groups which, by occupying different niches, reduced the possibilities of radiations within the archipelago. Therefore, most species originated by diverging in isolation from their source populations (allospeciation). Data from the Principe seedeater Serinus rufobrunneus showed that selection rather than drift was the main driver of divergence in allopatry, thereby supporting the applicability of the ecological model of speciation to allopatric situations. At the same time, the most divergent species were those that speciated after establishing sympatry with related populations, providing strong evidence for the importance of secondary contacts in promoting phenotypic diversification and speciation. Molecular evidence suggested that the São Tome grosbeak Neospiza concolor may have speciated in full sympatry - which if confirmed would make it unique among birds. In S. rufobrunneus, mate recognition traits were the first to diverge and may therefore be implicated in the first stages of the speciation process. This was further supported by playback experiments showing that populations no longer recognise the songs of foreign populations, suggesting that reproductive isolation may evolve as a by-product of independent divergence of mate recognition systems in allopatry. Overall, this study supported the view of speciation as a selection-driven process more likely to be completed in sympatry after an initial period of isolation. This is likely to constitute the most general model of speciation.
30

Growth of the insect embryo

Salzen, Eric A. January 1955 (has links)
No description available.

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