Though many heterotrophic decomposers and parasites are fungus-like, an organism must be in Kingdom Fungi to be considered a true fungus. In addition to genetic relationships, organisms are classified into Kingdom Fungi based on the following traits:
- Heterotrophic by absorption
- Morphology: Unicellular or a thallus composed of hyphae. If present, motile cells have only a single, whiplash flagellum (like us).
- Cell walls: Chitin
- Storage carbohydrate: Glycogen
- Life cycle: Haplontic (though this one gets a bit weird)
- Ecology: Many fungi are decomposers, primarily in terrestrial ecosystems. Other groups of fungi live in symbiosis with other organisms as parasites, mutualists, or commensalists.