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Can birds manipulate sex ratio of their offspring?
Tomiška, Lubomír ; Kratochvíl, Lukáš (advisor) ; Fuchs, Roman (referee)
The aim of this study is a summary of existing knowledge about skewed sex ratio in birds. This controversial topic represents one of the most important questions of evolutionary ecology. We still miss consistence in finding ultimate causes just as proximate mechanisms although there was an expansion of experimental studies already in the last decade of the 20th century which was caused by an invention of the new technology in sex determination. On the other hand, there are many convincing proofs of skewed primary, secondary, tertiary and even quartenary sex ratio so the facultative manipulation or obligatory sex ratio bias is presumable. My Bachelor's thesis compares studies focused on the similar ultimate causes and tries to point out their deficiencies together with contributions to research of this topic. Observation of sex ratio includes many specifics which are mentioned in theoretical introduction. The second part offers potencial proximate mechanisms which could be responsible for sex ratio manipulation. Within the analysis of studies I found sex ratio manipulation of the first egg in clutch as common trend which could fit to selective ovum resorption as a proximate mechanism.
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VPG in response to perception of male stimuli varying in states of undress and during different phases of sexual arousal
Čiženkova, Alena ; Krejčová, Lucie (advisor) ; Bártová, Klára (referee)
The human sexual response is a dynamic combination of cognitive, emotional, and physiological processes. To this day, not many studies have dealt with measurment of female sexual arousal in relation to the attractivness of presented stimuli or studies dealing with states of undress and different phases of sexual arousal of men presented by erection. The goal of the study was to test the difference in female sexual arousal during exposure to erotic photographs displaying men with different level of attractiveness and arousal. Female sexual arousal of 32 heterosexual women were measured by vaginal plethysmograph (BIOPAC system). Women showed increased genital arousal to attractive stimuli and to stimuli depiciting erected penis. The results showed that erected penis itself could be a sexual attractant regardless of model's attractiveness. Key words: female sexual arousal, vaginal pletysmography, male attractiveness
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Can birds manipulate sex ratio of their offspring?
Tomiška, Lubomír ; Kratochvíl, Lukáš (advisor) ; Fuchs, Roman (referee)
The aim of this study is a summary of existing knowledge about skewed sex ratio in birds. This controversial topic represents one of the most important questions of evolutionary ecology. We still miss consistence in finding ultimate causes just as proximate mechanisms although there was an expansion of experimental studies already in the last decade of the 20th century which was caused by an invention of the new technology in sex determination. On the other hand, there are many convincing proofs of skewed primary, secondary, tertiary and even quartenary sex ratio so the facultative manipulation or obligatory sex ratio bias is presumable. My Bachelor's thesis compares studies focused on the similar ultimate causes and tries to point out their deficiencies together with contributions to research of this topic. Observation of sex ratio includes many specifics which are mentioned in theoretical introduction. The second part offers potencial proximate mechanisms which could be responsible for sex ratio manipulation. Within the analysis of studies I found sex ratio manipulation of the first egg in clutch as common trend which could fit to selective ovum resorption as a proximate mechanism.
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