Final answer:
Fungi are heterotrophs, meaning they cannot produce their own food and rely on absorbing nutrients as decomposers of organic material, using structures like thallus and mycelium.
Step-by-step explanation:
Fungi are heterotrophs and can't produce their own food. Unlike autotrophs, they do not possess photosynthetic pigments like chlorophyll or organelles such as chloroplasts. Instead, they acquire nutrients by acting as decomposers, breaking down dead and decaying organic matter with external enzymes and absorbing the nutrients through structures such as a thallus or a mycelium. Their cell walls are composed of chitin, and they can reproduce both asexually and sexually through various cycles, including the production of spores.