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of Fungi Evolution:
Fungi, which evolved even before 900 million years ago,
are both evolutionarily intriguing and confounding. There are two main
theories on the evolution of fungi. The less accepted and older belief
is that fungi originally evolved from algae that had lost its chlorophyll.
Green algae evolved into simpler, lower level fungi, while red algae
evolved into ascomycetes. However, today this evolutionary theory is
viewed as outdated and has been replaced by another. The new hypothesis
states that fungi evolved from ancestral flagellates (called choanoflagellates)
such as algae and protozoa. Through time, some of these ancestral flagellates
lost their protistan flagellated stage in the fungi lifecycle, and transitioned
from aquatic to terrestrial environments to become ascoymcetes and basidiocycetes.
This theory still leaves many questions unanswered, and today scientists
are still working to map the genetic information of different species
of fungi. There are more than 56,000 known fungal species!
of Fungi (Phylums):
The fungi kingdom is divided into three major lineages,
Zygomycota, Ascomycota, and
Basidiomycota. However, the fungi kingdom goes far
beyond these three groups. It is divided into five different phyla:
Ascomycota, Basidiomycota, and
Mycomycota. However, there is also division of Deuteromycota,
imperfect fungi, which lumps together all the “puzzling”
fungi, which do not fit distinctly into any other phyla.
Division Chytridiomycota, being exceedingly simple
organisms, are the most similar to primitive fungi of any phyum
of fungi. They are crucial decomposers, feeding on living and
decaying organisms. They live in aquatic and semi-aquatic environments
(even damp soil), in both salt and freshwater bodies of water.
They are distinguished by their flagellated spores or gametes,
which help the reproductive units repel through water. In addition,
their walls are reinforced by chitin, and are the only fungi which
contain cellulose. Scientists examine Chytridiomycota to give
them an idea of what the first fungi looked like.
This terrestrial fungi is composed of approximately 900 species
and serves the main purpose of decomposing dead matter. They
live mostly in the soil, and include mycorrhizal fungi, black
bread mold, and a few animal parasites. Zygomycetes are named
for the particular way in which they reproduce sexually, extending
Ascomycota are characterized
by their production of spores in pods or sac-like structures
called asci. This phyla is the largest group of fungi with 50,000
species, and make up approximately 75% of all known species
of fungi. This phyla includes yeasts, lichens, and truffles.
There are three main groups of ascomycota: Archaeasomycetes,a
primitive group which seems to have diverged early in evolution,
and Hemiascomycetes and Euascomycetes, which are both more complex.
This phyla includes about 25,000 species and
include both edible and poisonous mushrooms, puffballs and others.
It includes truffles and many supermarket mushrooms. They are
commonly found in woodlands where they are key in the decomposition
of wood, and can often be recognized by their umbrella shape.
All Basitiomycota share a few main characteristics. All have
a multilayered cell wall, and produce ballistospores. All also
exist primarily in their dikaryotic stage, when two nuclei in
the same cell do not fuse. Only in one unique structure, “basidium”,
does fusing occur to form a diploid nucleus.
Mycomycota is the name for the fungi in lichens. Lichens are
composed of fungus and algae in a symbiotic relationship, as
the algae provides nutrients, while the fungus protects it from
the elements. Lichens photosynthesize light, with photoautotrauphs
located near the surface of the fungi. They have the ability
to erode rocks by growing into crevices. This allows them to
withstand extreme weather conditions, and allows for a long
lifespan. Lichens reproduce in three ways: fragmenting (extends
itself and then breaks into two or more pieces), production
of reproductive units, and then the reassociation of the parts
at the end.
These group is often called the “left-overs” and
do not fit clearly into any other group. About 25,000 species
are lumped into this category, including Trichophyton (Athlete's
foot), Penicillium (Penicillin), and Candida albicans ("Yeast"