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Ecological aspects of sexual reproduction
Toman, Jan ; Flegr, Jaroslav (advisor) ; Markoš, Anton (referee)
Sexual reproduction is one of the most interesting biological phenomena. No theory has ever entirely explained its wide occurrence among Eukaryotic clades despite its clear disadvantages (e.g. twofold price of sex). Theories can be divided into three groups according to the approach to solve this problem - molecular, genetic and ecological (environmental). Environmental theories are slightly preferred in the last decades and the opinion that the key to the sex enigma lies among them is widely accepted. Most of the environmental theories do not counter each other and there is possibility either to integrate them in several ways or presume that several of these theories might act simultaneously. According to theories, abiotically stable environments without biotic interactions (homogenous) should be suitable for and select for asexual species, whereas environments abiotically variable and rich in biotic interactions (heterogenous) should be suitable for and select for sexual species. The anagenetic phenomenon of punctuated equilibria and some of its explanations, e.g. P. R. Sheldon's Plus ça change hypothesis or J. Flegr's Frozen plasticity theory, also supports this division. There is a vast amount of empirical data supporting this division in ecological studies. Clearly homogenous environments...
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Ecological aspects of sexual reproduction
Toman, Jan ; Flegr, Jaroslav (advisor) ; Markoš, Anton (referee)
Sexual reproduction is one of the most interesting biological phenomena. No theory has ever entirely explained its wide occurrence among Eukaryotic clades despite its clear disadvantages (e.g. twofold price of sex). Theories can be divided into three groups according to the approach to solve this problem - molecular, genetic and ecological (environmental). Environmental theories are slightly preferred in the last decades and the opinion that the key to the sex enigma lies among them is widely accepted. Most of the environmental theories do not counter each other and there is possibility either to integrate them in several ways or presume that several of these theories might act simultaneously. According to theories, abiotically stable environments without biotic interactions (homogenous) should be suitable for and select for asexual species, whereas environments abiotically variable and rich in biotic interactions (heterogenous) should be suitable for and select for sexual species. The anagenetic phenomenon of punctuated equilibria and some of its explanations, e.g. P. R. Sheldon's Plus ça change hypothesis or J. Flegr's Frozen plasticity theory, also supports this division. There is a vast amount of empirical data supporting this division in ecological studies. Clearly homogenous environments...
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Lateral gene transfer and its utilisation for the phylogeny of eukaryotes
Novák, Lukáš ; Hampl, Vladimír (advisor) ; Čepička, Ivan (referee)
Lateral gene transfer is a relatively rare event in eukaryotes. Presence of a specific gene acquired by lateral transfer in multiple lineages can be therefore considered to be their common synapomorphy, defining them as a monophyletic group. In contrast to usual phylogenetic methods, this approach can potentially shed light even on the direction of evolution and therefore find the position of a root of a given group of organisms. In the first part of this work I discuss various aspects of lateral gene transfer utilisation in eukaryote phylogeny including advantages and disadvantages against common approaches. In the second part I present particular studies that have recently used this method. Key words: Lateral gene transfer, rare genomic changes, long branch attraction artefact, endosymbiosis, phylogeny, eukaryots, protists.
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The destiny of oocysts of \kur{Cryptosporidium} spp. in the enviroment in contact with different kinds of invertebrates
KOCIÁNOVÁ, Jitka
This study deals with occurrence, dispersion and destruction of Cryptosporidium oocysts in a particular environment. It therefore focuses on the contact with different kinds of invertebrates. It reveals, how oocysts get to contact with the invertebrates and what happens to them, whether they pass through their body and digestive tract. Next, the study describes, what happens, if the oocysts are excreted because some of the invertebrates could digest and destruct the oocysts and the other invertebrates could act the role of transmitters. The other information is about different methods, which can be used for detecting the oocysts in the environment or in the bodies of different kinds of invertebrates.
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