While fungi may be responsible for athlete’s foot and moldy food, in the ecosystem, fungi are very beneficial. They decompose dead organisms, fallen leaves, faeces, and other organic material, recycling chemical elements back into the environment.
What are Fungi?
Fungi are eukaryotes (have eukaryotic cells) and can be multi-cellular or unicellular. Fungi were once incorrectly grouped with plants, but they are more closely related to animals. Fungi are unique in the way they grow, reproduce and how they gain nutrients and in their structural organization.
How do Fungi Take up Nutrients?
Fungi are heterotrophs (organisms that can’t synthesize their own food and depend on organic substances for nutrition) and acquire nutrients by absorbing small organic molecules from the surrounding medium.
A fungus digests its food outside of its body. It does this by secreting a powerful hydrolytic enzyme into its food. These exoenzymes decompose complex molecules to simpler compounds, which the fungus can absorb.
Fungi are decomposers of the ecosystem. They decompose organic material, animal corpses, waste products and fallen logs, and this is how they gain nutrients. They often live as symbiotic (mutually beneficial) parasites; however, many fungi are pathogenic and cause disease.
Parasitic fungi absorb nutrients from the cells of living hosts. Mutualistic fungi also absorb a living host's nutrients, but they reciprocate with other beneficial functions, such as aiding the plant's ability to take up minerals from the soil.
Hyphae and Mycelia of Fungi
With the exception of yeasts, which are unicellular, fungi are constructed of tiny filaments called hyphae. Hyphae are composed of tubular walls around plasma membranes and cytoplasm. Hyphae form an interwoven structure called mycelia. Mycelia can be quite large but because they are below the soil surface, they usually go unnoticed.
Most fungi are multi-cellular and their hyphae are divided into cells by septa (cross-walls). Septa contain large pores to allow mitochondria, ribosomes and nuclei (organelles of cells) to flow between cells. The cell walls of fungi are different from plant cell walls, which are made of cellulose. Fungi cell walls are made of chitin, the same polysaccharide found in the external skeletons of insects.
Sexual and Asexual Reproduction of Fungi
Spores are then carried by the wind or water and germinate (to begin to grow or develop) to produce mycelia if they land in a moist, nutrient rich environment. Because spores can be carried by wind or water, they can be dispersed great distances, which accounts for the wide geographic distribution of many fungal species.
Fungi reproduce by releasing large amounts of spores (sometimes a trillion) into the environment. Spores can be produced sexually (reproducing by process involving both sexes), or asexually (independent of sexual processes, not involving the union of male and female germ cells).
Spores are then carried by the wind or water and germinate (to begin to grow or develop) to produce mycelia if they land in a moist, nutrient-rich environment. Because spores can be carried by wind or water, they can be dispersed great distances, which accounts for the wide geographic distribution of many fungal species.
The Benefits of Fungi for Humans
Humans have used fungi for centuries. Here are some common uses:
- Eating fungi, e.g., mushrooms
- Culturing fungi to produce antibiotics and other drugs
- Adding fungi to dough to make bread rise
- Using fungi to ferment beer and wine
Resource and further reading:
Campbell and Reece, 2002, 'Fungi', in Biology 6th edition, ed. Benjamin Cummings, San Francisco, chap 31.
Roberta Goli - Roberta has a Bachelor of Science Degree (Zoology), has worked with animals for over 10 years and enjoys writing short stories and flash ...
