Life Sciences Commons^™

Comparative Genomics Of Closely Related Salmonella Enterica Serovar Typhi Strains Reveals Genome Dynamics And The Acquisition Of Novel Pathogenic Elements, Kien-Pong Yap

Kien-Pong Yap

Background Typhoid fever is an infectious disease of global importance that is caused by Salmonella enterica subsp. enterica serovar Typhi (S. Typhi). This disease causes an estimated 200,000 deaths per year and remains a serious global health threat. S. Typhi is strictly a human pathogen, and some recovered individuals become long-term carriers who continue to shed the bacteria in their faeces, thus becoming main reservoirs of infection.

Results A comparative genomics analysis combined with a phylogenomic analysis revealed that the strains from the outbreak and carrier were closely related with microvariations and possibly derived from a common ancestor. Additionally, the …

Synthesis And Future Directions: What Have Harsh Environments Taught Us About Ecology, Evolution, Conservation, And Restoration?, Nishanta Rajakaruna, Robert S. Boyd, Tanner B. Harris

Nishanta Rajakaruna

No abstract provided.

Using Google Earth To Teach The Magnitude Of Deep Time, Joel D. Parker

Joel D Parker

Most timeline analogies of geologic and evolutionary time are fundamentally flawed. They trade off the problem of grasping very long times for the problem of grasping very short distances. The result is an understanding of relative time with little comprehension of absolute time. Earlier work has shown that the distances most easily understood by teachers and students are those most people can experience directly. Thus most timeline analogies are flawed by either overcompressing an experienceable time or relying on an unexperienceable distance. Under the constraint of experienceability, the best timeline to distance scale must be at least 75 miles and …

The Evolution Of Reduced Microbial Killing, Jan A.C. Vriezen Dr., Michael Valliere, Margaret A. Riley Dr.

Jan A.C. Vriezen Dr.

Bacteria engage in a never-ending arms race in which they compete for limited resources and niche space. The outcome of this intense interaction is the evolution of a powerful arsenal of biological weapons. Perhaps the most studied of these are colicins, plasmid-based toxins produced by and active against Escherichia coli. The present study was designed to explore the molecular responses of a colicin-producing strain during serial transfer evolution. What evolutionary changes occur when colicins are produced with no target present? Can killing ability be maintained in the absence of a target? To address these, and other, questions, colicinogenic strains and …

Evolution Of Delayed Reproduction Inuncertain Environments: A Life History Perspective, David N. Koons, C. J.E. Metcalf, S. Tuljapurkar

David N. Koons

Environmental uncertainty alone can select for delayed reproduction; however, its relative role in the evolution of delayed reproduction across life histories is not known. Along a life-history spectrum from low-survival/high-fertility species to high-survival/ low-fertility species, we show that the latter are more likely to evolve delayed reproduction if fertility varies over time. By contrast, if survival varies over time, low-survival life histories are more likely to evolve delays. If there is variation in both survival and fertility, and if this variation is positively associated, the evolutionarily stable reproductive delay is decreased (relative to independent variation in survival and fertility). Conversely, …

A Major Evolutionary Transition To More Than Two Sexes?, Joel D. Parker

Joel D Parker

Two recently discovered cases of genetic caste determination in social insects might provide the first example of a major evolutionary transition from two to more than two sexes. I argue here that the system can be interpreted as comprising primarily individuals requiring gametes from three parental types and having four sexes from the perspective of demographic extinction. Additionally, I show how this mating system can be seen as a major evolutionary transition. For these populations, it is apparent that the mechanism for a three- or four-sex system does not lie within the myriad of possible arrangements of chromosomes within individuals, …

Access To Another Mind: Naturalistic Theories Require Naturalistic Data, Mark A. Krause, Gordon Burghardt

Gordon Burghardt

If there is to be a natural theory of consciousness that would satisfy both philosophers and scientists, it must be based on naturalistic data and minimal clutter accumulated from semantic arguments. Carruthers offers a 'natural' theory of consciousness that is rather myopic. To explore the evolutionary basis of consciousness, a natural theory should include comparative psychological and neurological data that encompass nonlinguistic measures. Such an approach could provide a clearer picture of the adaptive function, mechanisms, and origins of consciousness.

Taxonomic Differences Between Birds And Mammals In Their Responses To Chemical Irritants, Russell Mason, Larry Clark, Pankaj Shah

Larry Clark

Ninety-five products are registered with the u.s. Environmental Pro­ tection Agency as bird damage control chemicals, but 38 (40%) are non­ lethal chemical repellents (Eschen and Schafer, 1986). Of these products, the active ingredients in 27 (71%) are methiocarb (a physiologic repellent that acts through food avoidance learning) or polybutene (a tactile repel­ lent). In general, chemical repellents are effective either because of aversive sensory effects (irritation), or because of post-ingestional ma­ laise (sickness). If the former, then chemicals are usually stimulants of trigeminal pain receptors (i.e., undifferentiated free nerve endings) in the nose, mouth, and eyes (Mason and Otis, …

A Model For Evaluating Time Constraints On Short-Term Reproductive Success In Altricial Birds1, Larry Clark

Larry Clark

We develop a simple single dimension model incorporating the time and energy commitments of breeding altricial birds in an effort to understand the evolutionary constraints on parental care. We chose time as the dimension of preference, because it is a naturally bounded constraint, e.g., length of day or breeding season. The utility of the model was evaluated by comparing simulations of time allocation of various breeding scenarios for the European starling (Sturnus vulgaris) to field data. The structure of the model may prove useful in determining the evolutionary constraints on parental care imposed by the developmental pattern of chicks.