Changing Definition of Fungi

• In the mid-twentieth century, the way that fungi were viewed by scientists changed several times. In 1952, Constantine Alexopoulos, a well-respected mycologist defined these unique organisms in a way that still stands today. As quoted in the "What Is A Fungus" section of the University of Hawaii website, he described fungi as being "nucleated, achlorophyllous organisms which typically reproduce sexually and asexually, and whose usually filamentous branched somatic structures are surrounded by cell walls." This definition helps in understanding fungi and their sometimes parasitic activities.
  
  

Achlorophyllus

• Understanding the term, achlorophyllus, is a must. Achlorophyllus is a scientific term that classifies an organism that cannot produce its own food. This includes all fungi. A synonymous term for acrorophyllus is heterotroph. By the way, organisms that can produce their own food are called autotrophs, and consist of mainly green plants.
  
  

Saprobe, Parasites and Symbionts

• Achlorophyllic organisms can be classified as either a saprobe, a parasite or a symbiont. Symbionts are organisms that depend on a host organism for their shelter, but the arrangement is beneficial to both species. A saprobe is a organism that can live off the remains of organic matter, which was once part of a living organism. A parasite gets its nourishment and shelter on another organism and can cause harm or disease to its host. Parasites are generally much smaller than their hosts.
  
  

Fungi as Saprobes

• Most fungi are saprobes. The mushrooms that you see growing out of dead logs and erupting from the earth are saprobes because they obtain their nutritional energy from the decayed organic matter of dead plants.
  
  

Parasitic Fungi

• Parasitic fungi can do quite a bit of damage to agricultural products. Blights and rusts are two types of fungi that do biological harm to our forests and agricultural plants. Some fungal organisms become parasites on animals or humans. Two fungi that are parasitic to humans are athlete's foot and ringworm.
  
  

One-celled vs. Multi-celled

• As defined in Section 2 by Mr. Alexopoulos, fungi are multi-celled organisms. When he says that fungi are structures that are surrounded by cell walls, he describes them as having an outer layer that contains many different cells. On the other hand, the terms saprobe and parasite are not limited to multi-celled structures. A one-celled organism can be a parasite or a saprobe.