Search

The aim of this work is to find out whether odor preference can affect the reproductive success of voles. Odors are generally able to reveal a lot of information about his carrier, according to which individuals may be able to choose a more compatible partner. With this partner, they increase the probability of transferring good genes to their offspring. The more investing sex is the one he chooses, and for most species it is the females. In the T-labyrinth, we gave the females a choice of odors from two males and, according to the time spent with one or the other, we evaluated the preference for one of them using a monitoring program. The females were then paired with either the male they preferred or the male they did not prefer. The number of pups from each pair was the main indicator for evaluating our results. These show that female voles are able to choose a more suitable partner according to their smell, with whom they produce more offspring.

In the view of the sexual selection research, the barn swallow (Hirundo rustica), and its European subspecies (Hirundo rustica rustica) in particular, belongs to the most detailed studied bird species all over. The males of the European subspecies have in general markedly longer outer tail streamers than the females have and, based on research in several European populations, this tail ornamental trait plays an important role in sexual selection in this subspecies. The length of the tail streamers was found to be related to several main parameters that are connected to individual attractiveness in socially monogamous pairing systems, such as early partner acquisition and earlier nesting initiation date, the probability of repeated nestings in a breeding season or the number of successfully raised young. The main aim of the presented diploma theses is to assess to what extend is the length of the tail streamers a determinative trait related to male attractiveness in a South Bohemian population of the European barn swallow. The results of this thesis imply that the tail streamer length of males is, indeed, an attractive trait in this population, connected to multiple mating advantages. KEY WORDS Sexual dimorphism, sexual selection, barn swallow, nesting initiation, attractivity, reproductive success,...

Mixed-ploidy populations, consisting of multiple cytotypes, are an optimal system for studying genome doubling consequences in plants. The role of frequency dependent selection, known as minority cytotype exclusion principle, is very important in them, but there are many factors limiting this selection. In my thesis, I evaluate the changes in cytotype frequencies and pattern in permanent plots in natural mixed-ploidy populations of three plant species - Butomus umbellatus, Knautia serpentinicola and Tripleurospermum inodorum and I also experimentally analyze partial aspects of frequency dependent selection towards minority cytotype in artificially established mixed-ploidy arrays of two plant species - Arabidopsis arenosa and Tripleurospermum inodorum. Varied changes in frequencies of minority cytotype ware revealed in permanent plots. Usually there was decrease, but in two plots there was increase in minority cytotype frequency and in one case it became dominant. Observed changes depend on initial frequencies of minority cytotype in populations, biological properties of species and particular environment of permanent plot. Relative indexes describing the frequency and the strength of disturbances and also the amount of soil nutrients was used to compare the environment of permanent plots across...

Human mate choice is far from random. Assortative mating can be either positive (homogamy), when people prefer and choose partners with self-similar characteristics, or negative (heterogamy, complementarity), when people prefer self-dissimilar partners. Over one hundred years of research, it has been shown that people generally couple based on the principle of homogamy. This thesis seeks to address the following two goals. First, it critically reviews the current state of knowledge in positive assortative mating (in particular, empirical support, factors affecting homogamy, mechanisms of homogamy, relationship and genetic impact of homogamy, and methodological pitfalls of research). This section includes theoretical papers deal with further mechanisms of assortative mating (homogamy, imprinting-like effect, heterogamy, complementarity). Second, the thesis provides further test of assortative mating in 'ideal partners' (preferences) and actual partners, in the context of sex, sexual orientation (heterosexual and non-heterosexual), and population (Brazil and Czech Republic). Results of these studies show that the principle of homogamy is valid irrespective of sex and population. However, they find a stronger tendency for homogamy in actual partners among heterosexuals than in homosexuals, although...

Two main principles of the relationship formation were previously established: i) homogamy and ii) heterogamy. According to the principle of homogamy, partners tend to be similar to each other. In contrast, heterogamy states that partners' characteristics differ. The theory of homogamy has reached significantly higher empirical support, however it is still unclear which mechanisms lead to similarities between partners. Potential mechanisms involve proximity (geography and social propinquity/proximity), preference for self-similarity, convergence (mutual assimilation) during cohabitation etc. Several previous studies showed, the similarity between partners in various social-demographic, physical, and attitudinal characteristics among others contributes to the relationship satisfaction. The main aim of the proposed bachelor thesis, is to perform a review of the relevant literature and analyse which mechanisms of homogamy and heterogamy apply to various characteristics and whether their role vary according to the type of the relationship (i.e. open relationships, marriages, etc.)

This bachelor thesis focuses on the issue of marriage, or more specifically, on the process of its formation or, in other words, mate selection. The author compares economic (G. S. Becker) and sociological (V. K. Oppenheimer) theory of the marriage market, including assortative mating. The subject of the work is to compare economic and sociological view of the issue of mate selection in an aim to discover common and different elements in the two scientific disciplines as regards the matter. The author works with four comparison criteria. The first one gives a general overview of the marriage market and describes how it functions, the second one shows the relationship between the marriage and job markets, the third is about assortative mating and the fourth one describes and explains changes in marriage behaviour in the second half of the twentieth century. Based on this, the author deems the sociological approach to be more adequate and suitable for investigating such a complex process as mate selection.

Multiplication of nuclear genome is considered one of the most important processes in the plant evolution. Neopolyploids arise in a diploid population by merging of two unreduced gametes or through "triploid bridge". However establishment of a new polyploid in the current population is not easy. Polyploid has to overcome through various mechanisms (like a self-pollination, nonrandom pollination, etc.) "the minority cytotype exclusion" and increase their frequency in the population. Diploids and polyploids differ in ecological demands and competition abilities. There is no correlation between ploidy and wide ecological amplitude or competition abilities. With the current knowledge, we can not determine in which case is the mixed population stable. There is an assumption that the population contains two closely related species simply can not be stable, and therefore all cytotype mixed populations are unstable. Powered by TCPDF (www.tcpdf.org)