This study was to determine reliability and validity for a two-tiered, multiple- choice instrument designed to identify alternative conceptions in earth science. Additionally, this study sought to identify alternative conceptions in earth science held by preservice teachers, to investigate relationships between self-reported confidence scores and understanding of earth science concepts, and to describe relationships between content knowledge and alternative conceptions and planning instruction in the science classroom. Eighty-seven preservice teachers enrolled in the MAT program participated in this study. Sixty-eight participants were female, twelve were male, and seven chose not to answer. Forty-seven participants were in the elementary certification program, five were in the middle school certification program, and twenty-nine were pursuing secondary certification. Results indicate that the two-tiered, multiple-choice format can be a reliable and valid method for identifying alternative conceptions. Preservice teachers in all certification areas who participated in this study may possess common alternative conceptions previously identified in the literature. Alternative conceptions included: all rivers flow north to south, the shadow of the Earth covers the Moon causing lunar phases, the Sun is always directly overhead at noon, weather can be predicted by animal coverings, and seasons are caused by the Earth's proximity to the Sun. Statistical analyses indicated differences, however not all of them significant, among all subgroups according to gender and certification area. Generally males outperformed females and preservice teachers pursuing middle school certification had higher scores on the questionnaire followed by those obtaining secondary certification. Elementary preservice teachers scored the lowest. Additionally, self-reported scores of confidence in one's answers and understanding of the earth science concept in question were analyzed. There was a slight positive correlation between overall score and both confidence and understanding. Responses on the questionnaire were investigated with respect to pedagogical choices. Evidence suggests that content knowledge and having alternative conceptions or science fragments may impact a teacher's pedagogical choices. Through careful development of instruments like ACES-Q II-R and other two- tiered, multiple-choice instruments, educators and researchers car not only identify possible alternative conceptions, they can raise an awareness of alternative conceptions held by children and adults. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]