Fungi are almost entirely multicellular with yeast, Saccharomyces cerviseaebeing a prominent unicellular fungusheterotrophic deriving their energy from another organism, whether alive or deadand usually Chytrids asexual reproduction worksheets some cells with two nuclei multinucleateas opposed to the more common one, or uninucleatecondition per cell.
Ecologically this kingdom is important along with certain bacteria as decomposers and recyclers of nutrients. Fungi are also important aiders of plant root function, as mycorrizhae. Examples of this diverse group are shown in Figure 1. These images are from http: The evolution of multicellular eukaryotes increased the size and complexity of organisms, allowing them to exploit the terrestrial habitat.
Fungi first evolved in water but made the transition to land through the development of specialized structures that prevented their drying out. First classified as plantsfungi are now considered different enough from plants to be placed in Chytrids asexual reproduction worksheets separate kingdom, and in fact are more like animals than plants.
Fungi contain unicellular, multinucleate, and multicellular forms. They are classified on the basis of their reproductive spores and the nature of their multinucleate or multicellular filaments known as hyphae. The structure of Penicillium is shown in Figure 2. Fungal cells have cell walls containing the carbohydrate chitin.
Chitin also occurs in the exoskeletons of the animal phylum arthropoda. SEM image color added of fungal mycelium with hyphae greensporangia orange and spores bluePenicillium sp. This image is copyright Dennis Kunkel at www. Fungi are absorptive heterotrophs: Fungal hyphae have a small volume but large surface area, enhancing the fungal absorptive capacity. Excess sugar is stored as the polysaccharide glycogen. This is also the storage product "Chytrids asexual reproduction worksheets" sugars in animals.
Fungal hyphae are collectively termed a mycelium. Some fungi are saprophytesthey obtain their food from the decaying bodies of plants and animals. Other fungi are parasites. All fungi, except the chytrids, lack flagella. Fungal reproduction thus mandates that the nonmotile gametes be brought together by the meeting Chytrids asexual reproduction worksheets opposite strains of hyphae.
Fungi are important both as a source of food and in the preparation of food. Edible fungi include mushrooms, truffles, and morels. Cheeses such as Gorgonzola, Roquefort, Stilton, and bleu have fungal colonies that give theses cheeses their distinctive flavors.
Beer and wine are produced through the action of fungi known as yeasts, such as Saccharomyces cerevisae. Many antibiotics, such as penicillin, are also produced by fungi. Fungi also are important crop parasites, causing loss of food plants, spoilage of food and some infectious diseases. Fungal parasites annually cause many billions of dollars in crop damage and food spoilage.
Over 60, species of fungi are known. Fungi are classified by their method of reproduction both sexual and asexual. It seems likely that fungi are not a monophyletic group. Historically they have been divided into four taxonomic divisions: Zygomycota, Ascomycota, Basidiomycota, and Deuteromycota. The last group, the Deuteromycota, are not a monophyletic group and thus have no standing in a modern classification scheme.
The modern systematic grouping includes Chytrids asexual reproduction worksheets Zygomycota, Ascomycota, and Basidiomycota, as well as the The Phylum Chytridiomycota include some of the oldest fungal fossils from the latest precambrian of Russiaas well as the presence of flagellated gametes.
Flagella are absent in the cells of all other fungi. All but one group of this phylum has chitin comprising their cell walls. Chytrids are aquatic, not terrestrial as are almost all other fungi.
They thus may provide us with a glimpse of the earliest fungi, both in habit as well as structure. This division also has quite a diverse arrayof body plans and habitats. Allomyces is a chytrid used in some experiments. The Phylum Zygomycota consists of fewer than species.
The zygomycete hyphae do not have one nucleus per cell, but rather have long multinucleate, haploid hyphae that comprise their mycelia. Asexual reproduction is by spores produced in stalked sporangiasuch as shown in Figure 3.
SEM of spores on a fruiting structure of Rhizopus x2, Sexual reproduction involved the fusion of haploid mating hyphae to produce a diploid zygosporea process shown in Figure 4. Sexual reproduction involving the formation of a zygospore.
Image from Purves et al. There are less than species of zygomycetes. Common bread molds are in this group, as are a few species that parasitize plants and animals. Most zygomycetes feed on dead
Chytrids asexual reproduction worksheets decaying plant and animal material.
Expose some bread to air for a few hours and it very likely will become infected with spores of a zygomycete. The Phylum Ascomycota contains more than 30, species ranging in body style from of unicellular yeasts to multicellular fungi such as morels. Yeasts reproduce asexually by budding and sexually by forming a sac or ascus. One yeast, Saccharomyces cerevisiaeis important for genetic research as well as its commercial applications in baking and brewing.
Yeasts are part of the Human Genome Project and serve as easily studied models for eukaryotic gene systems. Yeast chromosomes have also been modified to serve as vectors for transporting human DNA fragments for use in gene mapping. Other notable ascomycetes include Morchella esculentumthe morel, and Neurospora crassathe organism used by Beadle and Edward Tatum to develop the "one-gene-one-enzyme" hypothesis. Some ascomycetes also cause disease of can make chemicals associated with diseases.
In this group are Aspergillus flavuswhich produces a contaminant of nuts and stored grain that acts both as a toxin and the most deadly known natural carcinogen.
Candida albicans is another sac fungus that causes diaper rash and vaginal infections. Clearly this group, which may include nearly three-fourths of the fungal specis, offers humans both blessings as well as curses. Representtaives of this diverse group are shown in Figure 5. Morchella conicaa species of the edible fungu known as morels, image from http: Claviceps purpurea spurs on stalks of rye. Candida albicans - yeast and hyphae stages, this image is copyright Dennis Kunkel at www.
Sac fungi are also important in decomposing and recycling organic matter. Some ascomycetes are parasites responsible for Dutch Elm disease and Chestnut blight. Other sac fungi are used in commercial baking and brewing, wine making, and in the production of antibiotics, including some species of Penicilliumthe fungus that produced penicillin, the first of the wonder drugs. The term yeast is widely applied to ususally single-celled ascomycetes such as Candida albicans and Saccharomyces cerevisiae sold as brewer's yeast or baker's yeast.
The latter fungus is useful to humans as a leavening agent in bread as well as brewing of beer and similar
Chytrids asexual reproduction worksheets beverages.
These fungi typically are unicellular and reproduce by asexual budding as well as the sexual process involving the formation of asci. Claviceps purpurea, cause of the crop disease known as wild ergot or Jack-in-the-Ryeis a Chytrids asexual reproduction worksheets source of the hallucenogen LSD. Some sholars speculate that an outbreak of wild ergot may have been responsible for the hallucinations associated with the Great Awakening in 17th century America. The parasite Chytrids asexual reproduction worksheets the production of a long, dark purple spur hence the species name "purpurea" which contains the dormant fungus.
During this doimrant phase the fungus
Chytrids asexual reproduction worksheets several defense chemicals known as alkaloids, as well as lysegric acid and related compounds. These latter compounds can cause the reported psychotrophic effects. The deserts of the southwestern United States and northern Mexico as well as areas in South America are home top an endemic fungus, Coccidioides immitiswhich causes a disease in humans and animals known as valley fever.
The disease, formally known as coccidioidomycosis, usually begins as a respiratory infection. In the most severe cases death results, although most sufferers survive and are thought relatively immune for the remainder of their lives. If diagnosed properly there are medical treatments available. Rumors of the use of this organism as a bioweapon are thought to be just rumors, due to the extreme care needed to grow and work with this organism, whose infectious spores are approximately the size of large bacteria.
Those at higher risk from Coccidioides include those with immune systems AIDS patients, transplant recipients, diabeticscertain ethnicities, and those whose work exposes them to desert soils at certain times of the year.
This fungus, whose sexual stage is unknown at present, is of uncertain "Chytrids asexual reproduction worksheets" placement: Some ascomycetes are along with basiodiomycetes the symbiotic mycorrhizae fungi that are important to plant root function.
Plants with mycorrhizae grow better: Mushrooms, toadstools, and puffballs are commonly encountered basidiomycetes. These conspicuous features of the fungi are the reproductive structures known as fruiting bodies although they do NOT produce fruit, but rather, characteristic basidiospores. Sexual reproduction involves the formation of basidiospores on club-shaped cells known as basidiaas shown in Figure 6.