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Show 65 college of science Major evolutionary transitions in vertebrate history can potentially be directed and influenced by environmental changes by means of influencing phenotypic plasticity. During the Mesozoic, the divergent evolution of birds from nonavain theropods took place in atmospheric conditions where concentrations of oxygen (O2) and carbon dioxide (CO2) were lower and higher respectively, relative to present day levels The aim of this research was to explore the effects of these atmospheric variables on avian development with the aim of better understanding the role of phenotypic plasticity in avian evolution, especially of the respiratory system. Fertilized chicken eggs were incubated under different atmospheric conditions: first hypercapnia at 3% CO2, and then hypercapnea at 1% CO2; both trails had 21% O2 balanced with N2. Temperature and humidity remained constant across all trials and the con-trol was incubated under normoxia (~21% O2). During the incubation period individuals were pulled at specific stages (ED5, ED6, ED8, and ED10) and their development was compared to individuals from the control group. Depending on the stage and the development of the embryo specific developmen-tal markers or physical structures that were present were measured. Such measurements included embryo length and mass, limb lengths, organ ball mass, lung mass, length, width, and the lengths of different air sacs. After analysis of these measurements there appeared to be no significant difference in either the timing or size of these structures compared to the control. These findings could have been the result of several factors: small of a sample size; insufficient sampling intervals; a threshold effect for the gas treatment. Given the results from similar studies that focused on postnatal growth we have reason to believe that significant changes could be observed during later embryonic devel-opment, i.e. ED10 - ED18. One thing that was observed, however, was a considerable increase in chick mortality and deformity in the 3% trial compared to the 1% trail, indicating that there is some sort of threshold in regards to CO%. THE EFFECTS OF ATMOSPHERIC GAS CONCENTRATIONS ON THE DEVELOPMENT OF THE AVIAN LUNG Anthony Bell (Colleen Farmer) Department of Biology University of Utah UNDERGRADUATE RESEARCH ABSTRACTS Anthony Bell Colleen Farmer |