Ap Bio- Fungi

Topics: Fungus, Mycorrhiza, Ascomycota Pages: 7 (2009 words) Published: April 2, 2013
DOLP- Fungi

General Structure and Function:

For many years, fungi were classified into the plantae kingdom because the two kingdoms seemed to be alike; but now, we know that they are all too different. In fact, the fungi kingdom is more closely related to the animalia kingdom. Some of the only notable similarities between the fungi and plantae kingdoms are that they are both made of eukaryotic cells, both immobile, both contain cell walls (although made of different material), and both evolved from the protista kingdom.

The most major difference is that fungi have no chlorophyll. This means they cannot photosynthesize, and are thus heterotrophic. But fungi obviously aren't like animals, and don't have a stomach to digest their food in. There are various ways that fungi can receive their nourishment instead. The first thing they are able to do is secrete enzymes, called exoenzymes, to break down the complex molecules in their food into smaller organic compounds that they can easily absorb. Fungi that use this absorption method on nonliving organic material are called saprobes. If a fungi isn't saprobic, it would need to either a symbiotic partnership (where both sides benefit) or be a parasitic fungi (where it absorbs the nourishment off of a living host).

Most fungi are multicellular with eukaryotic cells, but some can be unicellular also, like yeast. Like plants, cells in fungi also have cell walls. But instead of being made of cellulose, it is made of chitin, a more flexible material. In general, fungi will have a basic structure of having a small filament (called hyphae) network that stretches out to invade the material that it will prey on, which is connected to a structure that will produce spores used in reproduction. The hyphae cells can either be septate or coencytic. Septate hyphae cells are separated with little walls that divide the hyphae so each division of the cell has only one nucleus. They also usually have pores that allow ribosomes, mitochondria, and even the nuclei to be exchanged between the cells. Whereas, coenocytic hyphae cells lack septa and are just a cytoplasmic mass that contains many nuclei. The way that the hyphae (mycelium) branches out to infiltrate the prey allows the fungi to utilize the material to maximum potential.

Fungi, as well as animals, are known to have evolved from a similar ancestor; an aquatic flagella-bearing protist. This is why fungi and animals are acknowledged as sister kingdoms. Chytrids (species in the phylum chytridiomycota), which were thought to have been the first of the fungi to branch off of the protista kingdom, still do have flagella. Many of the protists that were proven to have been ancestors of animals and fungi also have flagella. Proof that animals are more closely related to opisthokonts (members of the clade Opisthokonta, including animals, fungi, and protists) than to fungi implies that animals and fungi evolved from different ancestors.

Zygomycota is one of the five phylums of fungi. The name is derived from the zygosporangia that species in this phylum produce during reproduction. Species in the zygomycota phylum make up a tiny percentage (around 1%) of all fungi, because there are only approximately 1,000 species that are known today. Despite this, they are quite commonly seen. The bluish-green hued mold that grows on aged slices of bread is a frequent sight of a species of zygomycete, Rhizopus stolonifer. They are also the fuzzy mold that grow on expired produce. Besides molds, species of parasitic and commensal symbiotic zygomycetes also exist.


Rhyzopus stolonifer, from the example, would reproduce like this: Firstly, adjacent mycelia, with different mating types, would form gametangia (extension of the hyphae) which would enclose several haploid nuclei with and separate the two types with a septum. Then plasma’s, which is the fusion of the cytoplasm of the parents' mycelia, will occur. That...
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