What organisms are classified as fungi?

Fungi are primarily characterized as distinct organisms that can be either single-celled or multi-cellular, but the classification focuses particularly on their structural and functional characteristics rather than their size. The choice referencing single-cell organisms that form irregular masses accurately describes certain types of fungi, such as yeasts, which are unicellular fungi. These organisms can often take on irregular shapes during their growth.

Fungi are unique in their cellular structure, possessing cell walls made of chitin, a feature that distinguishes them from other living organisms like bacteria and viruses. Also, fungi play crucial roles in ecosystems, such as decomposers breaking down organic material and forming symbiotic relationships with plants.

The options referring to large multi-cellular organisms, bacteria, and viruses do not accurately represent fungi. While large multi-cellular organisms can include some fungi, they can also be animals and plants, making that description too broad and not specific to fungi. Bacteria, also living organisms, are fundamentally different from fungi, lacking the chitin-based cell walls. Lastly, viruses are not classified as living organisms in the same way as fungi; they require a host to replicate and do not possess cellular structures typical of fungi.