Is
a fungus more like a plant.... |
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..... or like an animal?
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For a long time, fungi were incorrectly grouped with green plants,
but they are not plants and neither are they animals (though they
have things in common with both)...
| Some fungi produce toadstools
in order to disperse their reproductive spores, and
these can look a bit like plants.... |
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... but, unlike plants, fungi CANNOT make their own
food by photosynthesis. Like animals, they have to obtain
their food from other organisms. |
| Most fungi have rigid cell walls,
like plants.... |
Diagram of a fungal hypha |
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... but true fungi do not contain
cellulose (the main component of plant cells walls).
Instead they have chitin...
like insect exoskeletons ! |
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| Fungi
form a kingdom of their own, the kingdom FUNGI.
Members of this kingdom share a number of common characteristics:
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1. Haploidy:
The members of this kingdom only have one set of chromosomes
in their nuclei. This state is described as Haploidy.
Only during their phases of reproduction do fungi become Diploid
and have two sets of chromosomes. |
2. Chitin:
Fungi, like plants, have cell walls. Unlike plants, however,
which have cellulose, a polysaccharide, as the main structural
polymer, fungal cell walls contain Chitin,
which helps give the fungal cell strength and shape. Chitin
is found in animals as well, with insects having chitin as
the support in their exoskeleton. |
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| 3. Hyphae & Mycelia:
True fungi tend to grow as a colony of cells strung together
in a filament called a Hypha (plural, hyphae
[>> more
information about plural forms of terms]). The cells in
a hypha may be separated by a cross-wall called a Septum,
which allows the flow of nutrients, but restricts organelles
to the cell in which they were made. Hyphae tend to form a
larger network of cells called a Mycelium
(plural, mycelia).
Diagram of a hypha
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Diagram of mycelial growth
(point at the spore
to make it 'germinate'!)
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4: Non-Motile Spores:
If a fungal biologist were to tell you that fungi have non-motile
spores, then what would that mean?
Fungi reproduce by haploid cells called Spores
which allow them to disperse their progeny over a large distance.
Other organisms have spores as well, but they tend to be Motile,
that is, they can actively move themselves, rather than rely
on air or water currents, animals and other mechanisms to
disperse them. |
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Beware:
Nobody told the fungi these four rules! There are a great number
of exceptions. Yeasts,
such as the baker’s yeast Saccharomyces cerevisiae,
don’t have a mycelial growth form, and Chytrids
don’t either (chytrids also have motile spores!). |
Diagram of yeast budding (point to
activate) |
To confuse the picture even further, not even the
experts can agree on what makes a fungus a fungus. Mycologists
(fungal biologists) study two other groups of organisms, the Oomycota
and the Myxomycota.
Oomycota are what are known as Pseudofungi –
they look like fungi, act like fungi, but aren’t fungi and
are more closely related to algae. Myxomycota are protists,
and have a phase in their life-cycle which resembles an amoeba.
As you can see, the Taxonomy,
or ordering of the Kingdom Fungi is in a state of flux. There is
a possibility that the textbook you are placing your faith in to
help you with your mycology may well be out of date!
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