Hamilton and Zuk (1982) proposed a model for parasite- mediated sexual selection in which females’ base mating choice on variable male traits, using the degree of expression of these traits as an indicator of heritable parasite resistance. This hypothesis is currently one of the dominant frameworks used to explain the relationship between parasites and the sexual selection of its host. Hamilton and Zuk’s hypothesis predicts that parasite intensity will be inversely correlated to both mating success and degree of expression of traits for males (Hamilton and Zuk 1982). While there is a significant amount of support for this hypothesis and prediction from empirical studies, there is roughly an equal amount of studies that report finding no relationship …show more content…
One assumption of the Hamilton- Zuk hypothesis is that full expression of secondary sexual characteristics in the host is limited due to parasitic infection (Hamilton and Zuk 1982). This assumption is meet under certain host- parasite systems, but failure to recognize the lack of generality that applies to this hypothesis could lead to experiments on inappropriate systems (Howard and Minchella 1990). Considering factors such as parasite life cycle and mode of transmission, it is clear that is assumption would likely not be meet by several parasite systems. If the studied host is acting as an intermediate host or the studied parasite is sexually transmitted it would not benefit the parasite to decrease mating success of the host by limiting expression of certain traits or increasing virulence (Luong and Kaya 2005). There may be many other aspects of the host- parasite relationship that could be important in parasite virulence and degree of expression of secondary sexual characteristics. For the purpose of this study parasite life cycle and mode of transmission will be further examined using previous empirical
An equal number of females and each type of male were introduced into each test tube, but in my own sample and those of others in the class there were mortalities throughout the experiment. Both some of the original flies and some offspring died during the experiment which could have influenced the results. If a vestigial fly died before it could mate that would give the wild type males an advantage in mating and producing a greater number of offspring. This would also be the case if any flies were harmed at any time during the mating period. To try and combat this problem the next time this experiment is done a larger number of male fruit flies could be used or more samples taken to try and reduce extremes in the data.
The experiment was conducted to test three different variables. These variables are an assessment of female aggressiveness, food deprivation, and staged male to female interactions. When testing the female aggressiveness, virgin females were run through a latency of attack assay to determine their aggressiveness. The spiders were given 30 seconds and a cricket was dropped in and a measurement was taken of how long interaction occurred between the cricket and the spider. When testing food deprivation, the number of days that female spiders went without food varied and was paired in groups of 1, 3, and 5 days for routine feeding. It was predicted that the longer female spiders went without food, the hungrier they would be. When testing staged male and female interactions, the males were placed in female containers with open lids as an escape route. Each pair interacted for six hours and all pairs resulted in successful copulation, sexual cannibalism, or the male abandons the female’s web. All instances of cannibalism were precopula and occurred shortly after males initiated their courtship sequence. After interaction, the remaining males were taken out the female web and females that cannibalized a male were given 24 hours to feed on the male before being given another male. A female never cannibalized two males consecutively. It was concluded that females that attacked prey more rapidly were more likely to cannibalize their first male mate. There is no detection of an association between cannibalism or food deprivation and female’s body mass. There is a positive association between the mass of egg cases and the number of offspring in females. The study proved that two factor are important in sexual cannibalism, female hunger state and female aggressiveness. There is also a source of fitness benefit for the female.
In some cases the eggs will get flushed out of the host. When this happens it releases miracidia that penetrate in to the snail. The snail is the intermediate host. When in the snail the organism uses asexual reproduction then development of cercariae. The cercariae can survive in...
Kopp, Elizabeth, and Medzhitov, Ruslan. “A Plague on Host Defense.” The Journal of Experimental Medicine. .
Disease and parasitism play a pervasive role in all life. Many of these diseases start with microparasites, which are characterized by their ability to reproduce directly within an individual host. They are also characterized by their small size, short duration of infection, and the production of an immune response in infected and recovered individuals. Microparasites which damage hosts in the course of their association are recognized as pathogens. The level of the interaction and the extent of the resultant damage depends on both the virulence of the pathogen, as well as the host defenses.
Merriam-Webster defines ‘parasite’ as ‘an organism that lives in or on another organism and benefits by deriving nutrients at the host 's expense’.
"Persistent female choice for a particular male trait values should erode genitive variance in male traits and thereby remove the benefits of choice, yet choice persists” (Miller, Christine and Allen Moore). This phenomenon is know as the Lek Paradox and has puzzled scientists for many years. Throughout all species there has been abundant evidence showing continuous female choice of male traits, yet there is still no definite answer as to what allows for genetic variance to be maintained, and why a specific trait never becomes fixed. Many hypotheses have been theorized and researched, all providing some explanation as to how this variance in species is maintained, from traits signaling resistance to parasites, according to Hamilton and Zuk, to the hypothesis of mutational and environmental affects. Condition-dependence can also provide information as to how the lek paradox is able to exist; this hypothesis will be looked at in this paper.
Females like to choose mates who have very bright colors as it is a sign of the male’s good health and vigor. The natural and sexual selection can affect populations in three ways: directional (environmental conditions change in a consistent direction; one extreme of phenotypes is favored), stabilizing (environmental conditions are relatively constant; intermediate phenotype is favored), and disruptive selection (environment has more than one type of useful resource; both extremes of phenotypes are favored). An example of directional selection is pesticide resistance since only the insects with a resistance are favored; an example of stabilizing selection is that the smallest lizards have a difficulty defending their territory whereas the largest lizards are most likely to be eaten by owls; an example of disruptive selection are the black-bellied seedcrackers since they either have a large beak (which they can use to eat had seeds), or a small beak (which allows them to eat soft seeds). Disruptive selection shows a balanced polymorphism, which is when two or more phenotypes are maintained in a
This parasite is spread through the bite of sandflies. There are three different types of infections and they each show varying degrees of severity. The cutaneous form produces mild skin ulcers, mucocutaneous produces ulcers in the mouth and nose, and the visceral form of the disease starts with skin ulcers and then fever, low red blood cell count, and an enlarged spleen and liver. The parasite is detected by a microscope and visceral can also be found by doing blood tests. 12 million people are in infected in 98 different countries and 2 million new cases are found every year. The disease also kills around 20 to 50 thousand people a year.
Sprecher, Susan, Quintin Sullivan, and Elaine Hatfield. 1994. “Mate Selection Preferences: Gender Differences Examined in a National Sample.” Journal of Personality and Social Psychology 66, 6: 1074-1080.
Some individuals have developed different traits to help them in the process of intra-sexual competition. The organisms with more distinctive traits have greater reproductive success. More genes of those traits are then ‘selected’ and are passed onto the offspring of the organisms. Throughout time variability in these traits becomes
As you can see, it is important to research sexual selection across various species’. Similar mechanisms of selection are present in all animals. By learning how these mechanisms act in one species, it is possible to gain insight into the behavior of all animals, including human beings.
In order to understand the present lifestyles relating to different approaches and tactics applied by humans in mate choice preferences, there is the need to refer to Darwin (1859, 1871) evolutionary perspectives. Darwin (1871) sexual selection is the driving force for males and females reproductive quest for their genes survival. These driving forces have been classified into two categories as intra-sexual and intersexual mate selection.Intersexual selection is male sexual selection process whereby males compete with other males and the females choose the strongest as their ideal partner. Intra-sexual selection occurs when the male species fight among themselves and the strongest gain access to females for
one in which the host animal can live for a long enough time for the parasite to
making them less prone to attack by fungi and insects. The use of sex pheromones