What are fungi?

Fungi, like plants and animals, represent a unique kingdom in the taxonomic organization of living organisms. They differ from plants and animals in their method of obtaining nutrients, in that they employ an absorptive mode of nutrition. Fungi secrete enzymes that break down large organic molecules in their surroundings and then absorb the products of these reactions for growth and reproduction. The majority of fungi are saprobes utilizing dead or non-living organic matter. Other fungi may be pathogens obtaining nutrients from plants, humans, or other animals and causing disease or death of the host. Still other fungi live as symbionts obtaining nutrients from another organism but not harming the other organism. Fungal symbionts often provide benefits to their symbiotic partner.

The Fungal Body

The body of most fungi is composed of long cellular tubes called hyphae, which typically branch and expand in a circular pattern. Hyphae are found in the soil or within other substrates in the natural environment. Aggregated hyphae form a larger structure called a mycelium. The mycelium, under certain environmental conditions, will give rise to an organized reproductive structure, often called a fruiting body. The mushrooms, bracket fungi, puffballs, and morels shown below are typical fruiting bodies. So beneath each of these structures, spreading throughout the substrate, lies the mycelium that gave rise to these structures. Fruiting bodies of other fungi are much smaller and many are microscopic in size. 

Fungal Spores