Ascomycetes are a group of fungi known for their unique reproductive structure called the ascus, which produces spores. They are one of the largest and most diverse classes of fungi, including species such as yeasts, molds, and truffles. Ascomycetes play essential roles in ecosystems, contributing to nutrient cycling and forming symbiotic relationships with plants. These fungi can be found in various habitats, from soil to decaying organic matter. Some Ascomycetes are important in food production, like yeasts used in baking and brewing, while others can cause diseases in plants and animals. Their ability to thrive in diverse environments makes them significant in both nature and industry.