EVOLUTION
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Theories 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 However, today this evolutionary theory is viewed as outdated and has been replaced by another.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!

Types 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: Chytridiomycota, Zygomycota, 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.

Chytridiomycota (Primitive Fungi):

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.




Zygomycota (Molds/Conjuction Fungi):

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 finger-like growths.





Ascomycota (Sac Fungi):

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.





Basidiomycota (Club Fungi):

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 (Lichens):

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.



Deuteromycota (Imperfect Fungi):

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" infections).


 

 

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Fungi Cladistics:

While people often associate plants and fungi as being closely linked, fungi are actually much more closely related to animals. The animal kingdom and the fungi kingdom are, in fact, sister groups, as both are heterotrophic. Both also originate from the same ancestral group, the flagellated protists called Choanoflagellates. However, fungi and plants ARE often in symbiotic relationships (see ecology). So next time someone says plants and fungi are the same thing... just say NO!

The major evolutionary break-throughs in the evolution of fungi (in order) have been the fallowing; from aquatic habitats to terrestial; changes in the frequency of sexual and asexual reproduction and production of spores; and in the case of lichens, whether or not the fungus is involved in symbiotic relationships with algal cells. (See graph below).


 

 

Sources:

All photographs acquired using google image search
All diagrams and illustrations are hand drawn by Jon, Chuck and Jesslyn
Cladogram adapted from:
http://www.sidwell.edu/us/science/vlb5/Labs/Classification_Lab/Eukarya/Fungi/
Info adapted from:
http://www.sidwell.edu/us/science/vlb5/Labs/Classificationß_Lab/Eukarya/Fungi/
http://www.perspective.com/nature/fungi/
All text written / website design done by Chuck Goldhaber, Jonathan Wachter and Jesslyn Jamison


EVOLUTION
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