BIOL 1020
FUNGI:
CHARACTERISTICS & CLASSIFICATION
OBJECTIVES
Discuss why fungi are not classified with plants.
Understand how fungi are fundamentally different from other living organisms.
Identify the distinguishing features of the four major groups of fungi.
Explain the role of fungi as decomposers.
Formulate and test a hypothesis that investigates the environmental conditions
necessary for mold spore germination and growth.
INTRODUCTION
There are four phyla traditionally recognized as belonging to the Kingdom Fungi that you
will learn about in this course. These phyla are the Chytridiomycota (chytrids), Zygomycota
(zygomycetes or sporangium fungi), Ascomycota (ascomycetes or sac fungi), and
Basidiomycota (basidiomycetes or club fungi). Fungi, like plants and animals, belong to the
domain Eukarya. Fungi are heterotrophs, but unlike animals, they secrete digestive
enzymes externally and then absorb the nutrients. Fungi are also very diverse. There are
unicellular and multicellular fungi. Also, some fungi reproduce sexually while others
reproduce asexually. Furthermore, there are fungi that are saprophytic (eat dead
organisms), while others are parasitic. The saprophytic fungi, along with saprophytic
bacteria, are essential decomposers; we rely on saprobes to break down dead organic
matter and recycle nitrogen and other inorganic nutrients back into the environment.
Some fungi form mutualistic relationships with a photosynthetic partner – either algae or
cyanobacteria – to form lichen. Species of this type of fungus are mainly found in the
phylum Ascomycota and a few are also found in the phylum Basidiomycota. Other fungi
form mutualistic relationships with plant roots as mycorrhizae. The fungi provide plant roots
with phosphate ions and other minerals from the soil and the plant roots provide carbon
from photosynthesis to the fungi. Most mycorrhizae are from the phylum Basidiomycota
and a few are from the phylum Zygomycota as well as the phylum Ascomycota.
Fungi have hyphae, which consist of a network of filaments that are composed of tubular
cell walls that surround the plasma membrane. The hyphae are like branches on a tree.
Fungi also have mycelium, which consist of an interwoven mass of hyphae that increases
the surface area for the absorption of nutrients from the soil. Mycelium is like the roots of a
plant because they extend outward into the soil.
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Fungi: Characteristics & Classification
BIOL 1020
LABORATORY ACTIVITIES
EXERCISE 1: FUNGAL BASICS
PROTOCOL:
This activity is designed to assess your basic knowledge of fungi. You may use the
introduction to this lab, your text, or other appropriate resources to answer the following
questions. Be sure your answers are in your own words and not copied directly from your
source material.
QUESTIONS:
1.
Fungi are evolutionarily more closely related to animals than they are to plants. List
and explain three pieces of evidence that support this statement.
2.
Like animals, fungi are heterotrophs; however, their means of acquiring nutrients is
quite different. Explain.
3.
Discuss how the sexual spores of chytrids, zygomycetes, ascomycetes, and
basidiomycetes differ from each other.
4.
How would the natural environment be altered if there were no saprophytic fungi or
bacteria?
5.
Provide one specific example that illustrates how fungi can be harmful to humans.
Your answer should identify a specific fungus and talk about the harm that it causes.
EXERCISE 2: CULTIVATING & COMPARING FUNGAL GROWTH
Molds and other fungi readily grow if they have an appropriate food source and a
hospitable environment. You may have unwittingly discovered this if you have ever left an
Fungi: Characteristics & Classification
BIOL 1020
orange or piece of bread sit for too long in the refrigerator or on the kitchen counter. In this
exercise you will design an experiment to evaluate how environmental factors influence the
growth of molds. You will design your experiment to answer one of the following questions:
1) Does mold grow faster at cold temperatures (in the refrigerator) or at warm
temperatures (in the room), or the same at both temperatures?
2) Does mold grow faster in the light or in the dark, or the same in both light and
dark?
3) Does mold grow faster in a moist environment or one that is dry, or the same in
both moist and dry?
4) Does mold grow faster on some substrates than it does on others, or does it
grow at the same rate on everything?
MATERIALS:
You will need one or more different substrate materials. You may choose to use bread
(preferably one without preservatives), fruit, cheese, a leaf, or another organic
substrate of your choice. You will only need more than one type of substrate if you
opt to test question 4 above.
Sealable sandwich-sized bags to hold the substrate you are testing.
A marker to label the bags
Damp (not wet) paper towels.
PROTOCOL:
1.
2.
3.
Choose one of the four questions above for your experiment. Formulate a hypothesis
and record it in the question section below. Remember, a hypothesis is a statement of
the expected outcome, so an appropriate hypothesis will indicate which, if either,
environmental situation you expect will produce better mold growth.
Design an experiment to test the question you have selected. Describe your
experimental protocol in the question section below. Unless you are specifically
testing question 3, each of your bags should contain the chosen substrate plus a
damp paper towel.
Think about how to design your experiment to answer your question as clearly
as possible. Plan to have a pair of experimental conditions that differ in only one
characteristic. For example, to test the effects of temperature put exactly the
same contents in all the bags and keep them all out of direct light, but keep
some of the bags at a different temperature. That way you can identify the cause
of any differences in mold growth that you observe.
Also, you will want to have at least two mold growth bags in each experimental
condition to see whether results are consistent for different mold growth bags
under the same condition. As stated above, these should be exact replicates.
Allow the bags to sit undisturbed for four – six days. Check the bags each day.
Record your observations in Table 1 below. If there is no noticeable growth, that
should be noted. When fungi start to grow, they will appear fuzzy or hairy, and may be
green, white, black, yellow, or other colors. Bacterial colonies can be distinguished
from fungal colonies as they will appear shiny or slimy, although they may also be
different colors.
Fungi: Characteristics & Classification
4.
BIOL 1020
At the completion of the experimental time period, answer the remaining questions
below.
TABLE 1. OBSERVATIONS OF FUNGAL GROWTH.
Bag 1
Bag 2
Bag 3
Bag 4
Specific
environmenta
l condition for
each bag:
Fill in the
dates below
Day 1 (the
day the
experiment
was started):
Day 2:
Day 3:
Day 4:
Day 5:
Day 6:
QUESTIONS:
1.
What question did you select to test?
2.
What is your hypothesis for this experiment?
3.
Write a paragraph to describe how you set up and carried out your experiment.
Fungi: Characteristics & Classification
BIOL 1020
4.
Write a paragraph that summarizes the results you obtained from your experiment. In
your summary you should compare all of the bags in a given experimental condition
(e.g. all the bags at one temperature). Did you find the same result in all of t
he bags
within each experimental condition? If you found differences between bags in the
same experimental condition, what might account for these differences? Your
summary should also note any differences you noticed between the bags in different
experimental conditions. For example, did mold growth differ depending on
temperature?
5.
Did your results support or refute your hypothesis? Explain.
6.
Based on the results from your experiments on mold growth, what can you conclude
about the factors that influence mold growth? What can you conclude about the best
ways to store food?
