609 research outputs found
Prospective students' and parents' attitudes towards a graduate-entry medical degree
No Abstract
How many years do students study before graduating in medicine?
Objectives. The Faculty of Health Sciences at the University of the Witwatersrand is considering changing from a 6-year medical degree to a mainly graduate-entry 4-year degree. The objective of this study was to determine how long students currently take to qualify and how many years are spent studying for each medical graduate produced.Design. A retrospective study of 691 students registered in medicine at the University of the Witwatersrand in 1988, 1989 and 1990 was conducted by examining student progress records.Results. The study found that an average of 7.89 years was spent studying for each graduate produced, including tertiary studies before medicine, repeated years and intercalated science degrees. Five hundred and eighty-nine students (85%) graduated and 102 (15%) did not. Fortyeight per cent studied for 7 or more years before graduating, 21% completed degrees before or during their medical studies, and 21% of students repeated years.Conclusion. The costs to the individual and society of the new 3 + 4-year degree structure would not be very different from those of the current 6-year structure
Agent-based modeling of multilevel selection : the evolution of feeding restraint as a case study
Evolutionary biologists are increasingly interested in the dynamics of multilevel selection, or selection acting simultaneously at more than one level in a hierarchy of reproducing entities (e.g., gene, chromosome, organelle, cell, organism, social group, multi-species community). Systems of linear equations are the usual tool for studying evolution, but are limited in their ability to capture important dynamics of multilevel selection. Here we use an agent-based model to study the evolution of cooperation in spatially structured populations. This work addresses the long-standing controversy over the role of group selection , or natural selection between versus within groups of interacting individuals. In an ecologically plausible setting, cooperative individuals with lower rates of food consumption. The results show that changing the spatial distribution of food, and thus the distribution of the individuals seeking it, can determine whether or not cooperation evolves. In this model cooperation evolved under a fairly wide range of parameter values, even without the kinship effects and discrete mixing phase that are sometimes thought to be necessary. We suggest that integrating equation-based analysis tools into agent-based models is a powerful way to study selection in systems with complex dynamics
RESPONSES TO CALF ENTANGLEMENT IN FREE-RANGING BOTTLENOSE DOLPHINS
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74984/1/j.1748-7692.1995.tb00280.x.pd
Chimpanzee Politics: Sex and power among Apes : By Frans B.M. de Waal. New York: Harper and Row, 1982, 223 pp., $16.50
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25846/1/0000409.pd
Reproduction in wild female olive baboons
The purpose of this paper is to evaluate several factors that influence female reproduction in a large troop of wild olive baboons ( Papio cynocephalus anubis ) based on 4 consecutive years of demographic data. Interbirth intervals were significantly shorter for females whose infants died before their next conception than for females whose infants survived. High-ranking mothers of surviving infants had significantly shorter birth intervals than comparable low-ranking mothers, independent of maternal age. This occurred mainly because the interval from resumption of cycling to conception was significantly shorter for high-vs. low-ranking females. Dominance rank did not influence sex ratio at birth, infant survival in the first 2 years, or adult female mortality. Age was also significantly related to interbirth intervals, with older females having shorter intervals. Primiparous females had consistently longer reproductive intervals than did multiparous females, but this difference reached statistical significance only for females whose infants died before the next conception. Primiparous females also experienced significantly higher infant mortality. Data on body size and estrous cycle length indicated no differences between high- and low-ranking females. Nutritional and stress-related mechanisms that may underlie the reproductive advantages of high rank are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/38425/1/1350190405_ftp.pd
Social relationships and ritualized greetings in adult male baboons ( Papio cynocephalus anubis )
Greetings involving exchanges of ritualized sexual gestures are a common form of interaction among adult male baboons, although relatively little attention has been paid to them. In this study, we investigate how greetings reflect important aspects of the male's social relationships, including dominance rank, age/residence status, and cooperative tendencies. The results are based on over 600 greetings among 12 adult males recorded during a 4-month study of a troop of wild olive baboons near Gilgil, Kenya. Four of the adult males were older, lower-ranking, long-term residents, which frequently formed coalitions to take estrous females away from the eight young, higher-ranking males. Virtually all dyads greeted: greetings occurred more than twice as often as other types of male-male interactions; and nearly all greetings occurred in a neutral context, in which there was no resource at stake. The percentage of greetings completed, the frequency with which different gestures were employed, and the roles adopted by each male varied significantly across old-old, old-young, and young-young dyads. Greetings between young adult males were often interrupted or actively resisted, consistent with their unstable and ambiguous dominance relationships. Greetings between old-old dyads were usually completed and appeared consistent with their cooperative relationships. One pair of old males formed a stable, reciprocal coalition against young males, and this pair's greetings showed remarkable symmetry of roles. Greetings, we hypothesize, function to allow males to negotiate important aspects of their relationships, including cooperation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44558/1/10764_2005_Article_BF02192786.pd
Gene flow and population structure of a solitary top carnivore in a human-dominated landscape.
While African leopard populations are considered to be continuous as demonstrated by their high genetic variation, the southernmost leopard population exists in the Eastern and Western Cape, South Africa, where anthropogenic activities may be affecting this population's structure. Little is known about the elusive, last free-roaming top predator in the region and this study is the first to report on leopard population structuring using nuclear DNA. By analyzing 14 microsatellite markers from 40 leopard tissue samples, we aimed to understand the populations' structure, genetic distance, and gene flow (Nm). Our results, based on spatially explicit analysis with Bayesian methods, indicate that leopards in the region exist in a fragmented population structure with lower than expected genetic diversity. Three population groups were identified, between which low to moderate levels of gene flow were observed (Nm 0.5 to 3.6). One subpopulation exhibited low genetic differentiation, suggesting a continuous population structure, while the remaining two appear to be less connected, with low emigration and immigration between these populations. Therefore, genetic barriers are present between the subpopulations, and while leopards in the study region may function as a metapopulation, anthropogenic activities threaten to decrease habitat and movement further. Our results indicate that the leopard population may become isolated within a few generations and suggest that management actions should aim to increase habitat connectivity and reduce human-carnivore conflict. Understanding genetic diversity and connectivity of populations has important conservation implications that can highlight management of priority populations to reverse the effects of human-caused extinctions
Hepatitis C virus infection rate in volunteer blood donors from the Western Cape - comparison of screening tests and peR
No Abstract
Adolescent male chimpanzees (Pan troglodytes) form social bonds with their brothers and others during the transition to adulthood
Social relationships play an important role in animal behavior. Bonds with kin provide indirect fitness benefits, and those with nonkin may furnish direct benefits. Adult male chimpanzees (Pan troglodytes) exhibit social bonds with maternal brothers as well as unrelated adult males, facilitating cooperative behavior, but it is unclear when these bonds develop. Prior studies suggest that social bonds emerge during adolescence. Alternatively, bonds may develop during adulthood when male chimpanzees can gain fitness benefits through alliances used to compete for dominance status. To investigate these possibilities and to determine who formed bonds, we studied the social relationships of adolescent and young adult male chimpanzees (N = 18) at Ngogo in Kibale National Park, Uganda. Adolescent male chimpanzees displayed social bonds with other males, and they did so as often as did young adult males. Adolescent and young adult males frequently joined subgroups with old males. They spent time in proximity to and grooming with old males, although they also did so with their age peers. Controlling for age and age difference, males formed strong association and proximity relationships with their maternal brothers and grooming relationships with their fathers. Grooming bonds between chimpanzee fathers and their adolescent and young adult sons have not been documented before and are unexpected because female chimpanzees mate with multiple males. How fathers recognize their sons and vice versa remains unclear but may be due to familiarity created by relationships earlier in development.Adolescent male chimpanzees, by age 12 years, have as many strong grooming bonds as do young adults.Research HighlightsAdolescent male chimpanzees form social bonds with other males.Bonds were common between unrelated males, but frequent with maternal brothers, peers, old males, and fathers.Fathers may be important for male chimpanzees transitioning to adulthood.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153616/1/ajp23091.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153616/2/ajp23091_am.pd
- …