Fungi can be unicellular yeasts or filamentous hyphae. Most fungi occur as hyphae that can be septate or coenocytic. Fungi are heterotrophs that can be saprophytes, symbionts, or parasites. They reproduce asexually via spores or sexually. Their vegetative phase is generally sedentary. Major fungal phyla include Zygomycota, Basidiomycota, and Ascomycota.