recap

29.1 recap

Fungi, like animals, are opisthokonts. Fungi are distinguished from other opisthokonts by absorptive heterotrophy and by the presence of chitin in their cell walls. Unicellular fungi called yeasts absorb nutrients directly across their cell surfaces. The body form of multicellular fungi—a mycelium made up of rapidly growing hyphae—allows them to practice absorptive heterotrophy efficiently in a variety of moist environments.

learning outcomes

You should be able to:

  • Explain how the structure of fungi facilitates their ability to decompose and consume other organisms.

  • Make inferences about the presence and abundance of fungi given different environmental features.

Question 1

How does fungal structure facilitate absorptive heterotrophy?

Unicellular fungi absorb nutrients directly from their environment, but multicellular fungi use structures known as hyphae for absorption. In both cases, fungi secrete digestive enzymes into the environment and then absorb the breakdown products through their cell membranes. The hyphae of multicellular fungi are long, thin networks that can penetrate soil and decaying or living organic material.

Question 2

What are the advantages and disadvantages to multicellular fungi of the large surface area-to-volume ratio of the mycelium? How does the mycelium restrict the types of environments in which fungi are generally found?

The large surface area-to-volume ratio allows rapid absorption over a wide area, as the hyphae can be immediately adjacent to the food source. However, this can also lead to rapid water loss and drying, which is why fungi tend to be restricted to (or at least thrive best in) moist environments.

616

Fungi are important components of healthy ecosystems. They interact with other organisms in many ways, some of which are harmful and some beneficial to those other organisms.