Pre-lab questions what is a model organism, and why is saccharomyces cerevisiae so often used as one? research and discuss the properties of mold that make them sometimes beneficial to humans, and sometimes potentially harmful. parasitic helminths are a major cause of disease in undeveloped countries around the world. discuss the role that microbiologists can and have played in to reduce the number of infections caused by parasitic helminths as well as diagnoses and treatments.