Fungi
Chapter 30
1
Shared Characteristics
•
Distinctive fungal features
– Fungi are heterotrophs.
– Fungi have several cell types.
– Some fungi have a dikaryon stage.
– Fungi have cell walls that include chitin.
– Fungi undergo nuclear mitosis.
2
The Body of a Fungus
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Fungi exist mainly in the form of slender
filaments (hyphae).
– mycelium - mass of connected hyphae
 grows through and penetrates substrate
3
The Body of a Fungus
•
•
Fungi cell walls are formed of polysaccharides
and chitin.
Mitosis is unique.
– nuclear envelope does not break down and
re-form spindle apparatus formed within
4
How Fungi Reproduce
•
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Differ from most animals and plants in that
each compartment of hypha can contain one,
monokaryotic two dikaryotic or more nuclei
Many nuclei intermingle in cytoplasm of
fungal mycelium which can lack distinct cells
– heterokaryotic – nuclei from genetically
distinct individuals
– homokaryotic – hyphae whose nuclei are
genetically similar to one another
5
How Fungi Reproduce
•
Fungi are capable of both sexual and asexual
reproduction.
– Fungi reproduce sexually after two hyphae
of opposite mating type fuse.
 in some fungi fusion two haploid cells
immediately results in diploid cell (2n)
6
How Fungi Reproduce
•
Spores most common means of
reproduction
– may form from asexual or sexual
processes
– most often dispersed by wind but some
spread by insects or other small animals
7
How Fungi Obtain Nutrients
•
•
All fungi obtain food by secreting digestive
enzymes (exoenzymes)
absorb the organic molecules produced
(external digestion).
– hyphae network SA for absorption
– many fungi able to break down cellulose in
wood
8
•
•
•
Anaerobic fermentation provides flavor for
wine and cheese.
Fungi are decomposers
Fungi often act as disease-causing
organisms for both plants and animals.
9
Ecology of Fungi
•
Mutualistic associations
– lichens - fungi and green algae
– mycorrhizae - fungi and plant roots
10
Four Major Groups of Fungi
•
Four major groups
– Chytridiomycota
– Zygomycota
– Basidiomycota
– Ascomycota
11
Chytridiomycota
•
aquatic, flagellated fungi
– most closely related to ancestral fungi
12
Zygomycota
•
•
includes common bread molds
hyphae produce clumps of erect stalks - sporangiophores
form sporangia
13
Basidiomycota
•
Most familiar fungi (mushrooms, toadstools,
puffballs, rusts, and smuts)
– named for characteristic sexual
reproductive structure, basidium
14
Ascomycota
•
•
Very large group including yeasts, common
molds, and morels
Named for reproductive structure ascus
15
Ascomycota
•
Yeasts
– unicellular - most reproduction is asexual
and takes place by cell fission or budding
 ferment carbohydrates
 play a leading role in genetic research
16
Lichens
•
Lichens are symbiotic associations between a
fungus and a photosynthetic partner.
 fungal hyphae penetrate photosynthetic
cells and transfer nutrients to fungal
partner.
17
Mycorrhizae
•
Roots of about 90% of all kinds of vascular
plants are involved in mutualistic symbiotic
relationships (mycorrhizae).
18
Mutualistic Animal Symbioses
•
A range of mutualistic fungal-animal
symbioses has been identified.
– ruminants
– leaf-cutter ants
19
Fungal Parasites and Pathogens
•
Aflatoxins - carcinogenic compounds
produced by strains of Aspergillus flavus
– grows on corn, peanuts, cotton seeds
20