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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.
501

Secular changes in sexual and natural selection against deleterious genetic mutations in humans

Arslan, Ruben C. 25 October 2017 (has links)
No description available.
502

2008 U.S. Presidential Elections / Americké prezidentské volby v roce 2008

Siničáková, Veronika January 2009 (has links)
The aim of my thesis is to analyze the process of the 2008 U.S. Presidential Election and identify the factors that had the biggest influence on the election results. The paper is divided into three chapters. The first chapter describes the rules for electing the U.S. president, the second chapter focuses on issues and the third on other factors that decided the election. My thesis is thus a study of how the U.S. president was elected in 2008 and of the issues currently most discussed in the American society.
503

Sélection sexuelle et évolution des ornements femelles : une étude de la coloration du plumage femelle utilisant des analyses comparatives et des jeux de données à long terme issus de populations de mésange bleue (Cyanistes caeruleus) / Sexual selection and the evolution of female ornaments : an examination of female plumage colouration using comparative analyses and long-term data sets collected in blue tit (Cyanistes caeruleus) populations

Fargevieille, Amélie 13 December 2016 (has links)
Les traits ornementaux sont classiquement vus comme un attribut des mâles chez les espèces animales. Cette vision est liée à un rôle considéré historiquement comme très asymétrique des sexes, avec les mâles qui entrent en compétition (sélection intra-sexuelle) pour attirer les femelles qui choisissent (sélection intersexuelle) le meilleur partenaire. Cette idée fut développée en liaison avec l’asymétrie dans la production des gamètes mâles et femelles. Les femelles, qui produisent un nombre réduit de gamètes de grosse taille, maximisent la chance de survie de leurs descendants en investissant plus dans les soins parentaux ; elles deviennent ainsi le sexe limitant et choisissent les mâles qui entrent donc en compétition pour avoir accès à la reproduction. Tout trait ornemental qui augmente le succès d’appariement sera donc avantageux pour les mâles conduisant à des traits sexuels secondaires plus développés chez ce sexe. Si les traits ornementaux sont fréquents chez les mâles, il existe également de nombreux exemples chez les femelles, notamment chez les espèces socialement monogames à soins biparentaux. C’est seulement récemment que les biologistes évolutifs ont cherché à tester les processus expliquant l’apparition et le maintien des ornements femelles. Si le rôle de la corrélation génétique dans cette évolution est incontestable, et que la sélection sociale est aussi majeure, plusieurs études empiriques ont montré un choix mâle pour les ornements femelles et des modèles théoriques ont déterminé les paramètres conduisant à l’évolution du choix mâle. Par ailleurs, les approches phylogénétiques retraçant l’évolution des ornements ont montré une forte labilité des traits femelles, avec des apparitions et disparitions de traits ornementaux plus fréquentes chez les femelles que chez les mâles. Afin de mieux comprendre la relation entre la sélection sexuelle et l’évolution des ornements femelles, cette thèse s’est construite sur ces résultats précédemment acquis et a mené plusieurs approches pour mieux préciser le rôle de la sélection sexuelle dans l’évolution et le maintien de la coloration chez les femelles. Une approche comparative à l’échelle des passereaux a testé les paramètres déterminés comme conduisant à l’évolution du choix mâle par des modèles théoriques. En accord avec les modèles théoriques, les résultats mettent en avant l’importance de l’investissement du mâle dans les soins parentaux dans l’évolution de la coloration du plumage femelle. Ils montrent également comment l’investissement initial des femelles dans la reproduction limite l’évolution de la coloration femelle. Un autre axe de la thèse s’est focalisé sur la coloration chez une espèce monogame, la Mésange bleue Cyanistes caeruleus, en utilisant un vaste jeu de données à long terme avec10 ans de donnés dans quatre populations pour tester notamment(i) la force de la corrélation génétique, (ii) les liens entre indices de succès de reproduction et coloration et (iii) l’existence d’un appariement par homogamie chez cette espèce. Si les résultats principaux montrent une forte corrélation génétique et soulignent une très forte variation spatiotemporelle, l’application d’outils méta-analytiques a permis de déceler une relation entre les colorations des femelles et les indices de succès de reproduction ainsi qu’un patron faible mais positif d’appariement par homogamie pour les deux patchs étudiés (couronne et bavette). Les deux volets de la thèse représentent de nouveaux apports en faveur de l’évolution des ornements femelles. Ils soulignent la complexité associée à leur évolution et l’importance de prendre en compte la variation spatiotemporelle pour une compréhension étendue et une possibilité de généralisation. / Ornamental traits are classically associated with males in animal species. The asymmetrical view is related to sex roles, in which males are competing (intra-sexual selection) to attract females which chose the best mate (intersexual selection). This idea was developed with the concept of anisogamy, the asymmetry in the production of male and female gametes. Females producing few but large gametes maximize their offspring survival rate by investing more in parental care; they become the limiting sex and chose males which are thus competing for access to reproduction. Then, any ornamental trait increasing pairing success would become advantageous for males, leading to more developed secondary sexual traits in this sex. If ornamental traits are more frequent in males, there are also many examples with females, especially in socially monogamous species with biparental care. Evolutionary biologists have only started recently to test processes explaining the outbreak and maintenance of female ornaments. Genetic correlation is an unquestionable process involved in this evolution, and social selection is also a major process. Several empirical studies have also related male mate choice to female ornaments and theoretical models have defined key parameters driving the evolution of male mate choice. Furthermore, phylogenetical studies retracing the evolution of ornaments have showed a high lability in female traits, with more frequent gains and losses of ornamental traits in females compared to males. In order to link sexual selection to the evolution of female ornaments, this thesis was based on these previous achievements to develop different approaches to better understand the role of sexual selection in the evolution and maintenance of female colouration. Comparative methods in songbirds tested the key parameters defined by theoretical models as driving the evolution of male mate choice. In line with theoretical models, results highlight the importance of male investment in parental care in the evolution of female plumage colouration. They also show how female initial investment in reproduction limits this evolution. Another thesis axis focused on colouration in a monogamous species, the Blue tit Cyanistes caeruleus, using a large dataset across 10 years in four populations and tested in particular (i) the strength of genetic correlation, (ii) relations between proxies of reproductive success and colouration and (iii) the existence of assortative mating in this species. The main results highlight a strong genetic correlation and a wide spatiotemporal variation and the use of meta-analyses revealed correlation between female colouration and proxies of reproductive success as well as a weak but positive pattern of assortative mating on the two measured patches (crown and chest). Both sides of the thesis represent new insights in favour of the evolution of female ornaments. They also highlight the complexity associated with their evolution and the importance of considering spatiotemporal variation for extensive understanding and generalisation.
504

Výskyt a role UV reflektantního zbarvení u listorohých brouků (Coleoptera: Scarabaeidae) / The distribution and role of UV reflectant patterns in Scarab beetles (Coleoptera: Scarabaeidae)

Vlach, Jan January 2021 (has links)
The diploma thesis is focused on the distribution and role of UV reflectant patterns in beetles (Coleoptera) with focus on the family Scarabaeidae. Through a survey of European museum collections, we discovered over 900 species of UV reflectant beetles, of which 850 species were identified as UV reflectant for the first time. The surface structures responsible for UV reflectant patterns in beetles were studied in detail using a scanning electron microscope. We have identified two ways how the UV reflectant patterns occur. The first way: the light rays interact with the internal structure of the cuticular formations or the cuticle itself; the second way: the light rays interact with the surface layer formed by cuticular secretion. Additionally we carried out experiments with live animals, where we investigated the effect of an individual's age on the intensity of UV reflectant patterns and the effect of UV reflectance on reproductive activity. In a pilot study we were able to show that freshly hatched individuals show a higher level of UV reflectance than older individuals.
505

Vliv orální hormonální antikoncepce na ženskou sexualitu: evolučně psychologický přístup / The influence of oral hormonal contraceptive use on female sexuality: the evolutionary perspective

Klapilová, Kateřina January 2011 (has links)
The proposed thesis is comprised of eleven papers connected by the employment of the evolutionary psychological approach in research on various aspects of human sexuality. The aim of the first monothematic part is to demonstrate the evolutionary-psychological approach to one recent phenomenon in female sexuality - the use of oral contraceptives (OC). OC use has been shown to suppress psychological mechanisms that are considered to be adaptive in the fertile period of the natural menstrual cycle. In particular, OC users' ratings of male stimuli that provide the cues of genetic quality and compatibility are lower in comparison with normally cycling women. Moreover, the increase in sexual desire and in the prevalence of proceptive behaviour observed during mid-cycle in normally cycling women is diminished. However, the impact of this phenomenon on mate-choice and relationship dynamics in an ecological context has not been studied. In the first study, we have analyzed the data of Czech women obtained via representative sampling within the Czech National Survey of Sexual Behavior. Results indicated that normally cycling women had a significantly higher number of one-night stands during the last year in comparison to OC users even when living in a long-term relationship. OC usage was also shown to have...
506

Reduction of Competition Between Bisexual and Unisexual Females of Poecilia in Northeastern Mexico

Balsano, Joseph S., Kucharski, Kristine, Randle, Edward J., Rasch, Ellen M., Monaco, Paul J. 01 February 1981 (has links)
Breeding compexes of poeciliid fishes with a bisexual and two unisexual species were studied for mechanisms permitting Sympatric coexistence. The unisexuals are gynogenetic and thereby sexually dependent on the males of the bisexual species for sperm to initiate development, but inheritance is entirely maternal. Bisexual females are more abundant in headwater localities; unisexuals increase in downstream localities. Males were 10 - 18% of the total poeciliid population, regardless of the relative proportions of bisexual to unisexual females. Downstream localities were typified by greater habitat diversity, including a variety of backwater pools. The unisexuals showed a marked preference for such pools. Both field and laboratory studies showed that all three types of females as well as males preferred shaded areas with a gravel substrate. Although the four types of fish were found together, nearest neighbour data indicated that each type of female preferred its own kind. Males courted throughout the year and were indiscriminate in their choice of mates. Despite the skewed sex ratio, males were not in short supply because only a few females were sexually receptive at a given time. No significant differences existed between bisexuals and unisexuals in their relative reproductive outputs, but they were asynchronous.
507

Male Aggression, Limited Female Choice and the Ontogeny of Mating Behaviour in the Flesh Fly Sarcophaga Crassipalpis

Dylan Shropshire, J., Moore, Darrell, Seier, Edith, Joplin, Karl H. 01 December 2015 (has links)
1
508

Do Adult Romantic Attachment Empathy and Social Skills Influence Mate Poaching Infidelity?.

Gorniewicz, James Stephen 07 May 2011 (has links) (PDF)
The present study examined the possibility that adult romantic attachment orientation, empathy, and social skills could either individually or jointly influence the expression of mate poaching behaviors. Participants (N = 404) were recruited from a Southern Appalachian university and ranged in age from 18-60 years, with a mean of 21. Data were collected using a web-based survey system. Results of this study lend support to the growing literature demonstrating a link between adult romantic attachment and mate poaching. Additionally, the present study also added to the literature by showing for the first time 1) a relationship between empathy and mate poaching and 2) a relationship between social skills and mate poaching. Contrary to one of the hypothesized structural models, adult attachment was not found to mediate the relationships between 1) empathy and mate poaching and 2) social skills and mate poaching.
509

Exploring female preference for male melanic pigmentation patterns in the Malawian cichlid <i>Metriaclima zebra</i>

Medina García, Angela L. 08 November 2011 (has links)
No description available.
510

Effects of sex ratio on ontogeny of sexual behavior and mating competence in male guppies, poecilia reticulata

Field, Kristin L. 29 September 2004 (has links)
No description available.

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