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- Characteristics of Fungi:
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- 1. Fungi are eukaryotic
- 2. The majority are multicellular
( yeast is single celled)
- 3. Lack chlorophyll
- 4. Nutritionally they are heterotrophic,
they digest food outside the body and absorb it .
They are saprophytes, parasites and some are mutualistic.
- 5. Their basic body plan constitutes
a mass of netlike filaments called hyphae.
The entire mass is called the mycelium. Most
fungal hyphae are divided into cells by cross walls
called septa. Some fungi are aseptate, lacking cross
walls. They are said to be coenocytic. Some types
of fungi contain lateral hyphae that absorb nutrients
from other organisms, called haustoria.
- 6. Reproduction is accomplished by
the release of sexual or asexual spores. For many
species of fungi sexual reproduction is a contingency
used when environmental conditions are difficult.
Under favorable conditions asexual spores are produced
by the millions and dispersed over a large area.
- Haploid conditions prevail in the
life cycles of most fungi. Conjugation occurs in many
fungal species.
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- Diversity of Fungi:
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- Fungi are classified into units called
Divisions. There are 4 divisions based primarily on
variations of sexual reproduction. The names of the
divisions are based on the sexual structure that characterizes
that group of fungi.
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- 1. Division Zygomycota:
These are mostly terrestrial fungi that live in soil
or on decaying plant or animal material. Their hyphae
are coenocytic, with many haploid nuclei. Asexual
spores, usually wind swept, are produced by structures
called sporangia, at the tips of aerial hyphae.
Sexual reproduction involves the formation of resistant
bodies called zygosporangia that can remain dormant
when the environment is too harsh for growth. Examples
are black bread mold ( Rhizopus stolonifer).
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- Division Ascomycota:
These are sac fungi. They range from unicellular yeast
to large cup fungi. The sexual reproductive structure
is the asci, a small sac like structure. These
asci are packed into large fruiting structures called
ascocarps. The hyphae are multicellular septate structures.
They lack sporangia but reproduce asexually by producing
chains of spores at the tip of specialized hyphae.
These spores are called conidia. Two types
of spores are produced by this type of fungus, conidia
and ascospores. Conidia are asexual, while
the ascospores are sexual.
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- Reproduction of Ascomycetes:
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- These fungi are important in decomposing
lignin and collagen of dead plants and animals. Some
are mutualistic ( lichen) and many are parasitic to
plants ( powdery mildew and Dutch elm disease).
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- Division Basidomycota:
The mushroom, shelf fungi, puffballs and stink horns
are examples of this division. The name is derived
from the sexual reproductive structure called the
basidium. The club like shape gives the name
to some of the most common fungal types in this division.
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- Reproductive cycle of the mushroom:
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- Division Deuteromycota:
These organism have no known sexual life style. They
are also known as fungi imperfecti. Examples of this
group are Penicillium and Arthrobotrys.
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- Lichens: Highly integrated
symbiotic associations of millions of algal cells
tangled in a lattice of fungal hyphae. Classification:
leafy ( foliose), fruticose ( shrubby), and crustose
( crusty).
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- Mycorrhizae: mutualistic association
of a fungus and a root. 90% of the fungi is bascidomycota
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