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| Pilobolus |
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| ‹ Kingdom Fungi › |
| Kingdom Fungi is a very diverse group of organisms that include (but are not limited to); mushrooms, molds, and yeasts.They are eukaryotic heterotrophs (absorption of nutrients from the enviroment) that are all multicellular with the exception of the yeasts. Most fungi are composed of thread-like individual filaments called hyphae, organized into a larger body called the mycelium. Fungi are important in the lives of many other organisms, particularly plants and humans. Most can decompose dead organic material into inorganic nutrients, an important role they play in many plant life cycles. Fungi can also break down other materials, including harmful toxic compounds, making them very useful to humans in the form of medicines and antibiotics. |
| Links: |
| Rhizopus |
| This fungi can be easily recognized as a common bread mold, although it's range of food is not limited to bread. It's composition is like that of most fungi; hypae and cell walls made of chitin. Rhizopus is characterized by dark sporangia containing dark (sometimes pale) spores. Rhizopus tends to grow very fast, and it's spores can spread very easily via air, making it an easy contaminent in laboratories and homes. |
| Links: |
| Pilobolus |
| Known as the "dung fungus", Pilobolus grows natrually on animal dung such as cow, rabbits, and other grass eating animals. It uses excrement for food, as it decomposes the material into useful nutrients for plants and soil organisms. Without Pilobolus, dung would not decompose and would thus be laying around for a very long time. How this fungus gets into the dung is through the animal eating it's spores (normally in grass) and excreting them with their dung. The spores get to the grass from the Pilobolus parent "shooting" it's spores far away from it's location in dung to areas of vegetation around it, where the animal can then eat the spores and start the cycle over again. This gives rise to the alias as the "shotgun fungus" that many people use to describe Pilobolus. |
| Links: |
| Podaxis |
| This type of Fungi is very unique in that its gills are not exposed to the environment like most other types of fungus. Podaxis is very common in Australia and has been used for many strange things throughout time. For example, its spores were used by many desert tribes to darken the white hair of old men’s whiskers and for body painting. Podaxis is commonly found on termite mounds and other places that resemble that environment. |
| Links: |
| http://www.anbg.gov.au/fungi/aboriginal.html |
| Lichens |
| Lichens are important members of the desert (cryptobionic) crust. This “crust” is a layer that, if it remains undisturbed, covers much of the soil between vascular plants. This layer can help retain moisture and prevent erosion. A major component of the desert crust is lichens. Lichens represent a symbiotic relationship between fungi and green algae or cyanobacteria. Lichens can survive extreme temperatures, specifically drought. To do this, the lichen completely dries out and becomes dormant. When moisture is available again, they quickly absorb it and can be photosynthetic again. |
| Links: |
| http://www.cwnp.org/lichen.html |
| ‹ Bryophytes › |
| Bryophytes refer to a group of plants that belong to the mosses, the liverworts, or the hornworts. Bryophytes play a major role in maintaining the ecosystem’s humidity level, by their ability to absorb and retain water. It is important to remember that bryophytes are not vascular plants and do NOT have a true vascular system, meaning they do not have a well developed system for conducting water and minerals. It is because of this fact that they are considered fairly primitive plants. The gametophyte (n) condition is dominant. |
| Mosses |
| Moss is the dominant
component of the desert (cryptobionic) crust. An important thing to remember
about mosses is that the gametophytic (n) portion of the plant is always
leafy. The sporophyte (2n) condition is long lived and looks like small
brown stalks located on the top of some gametophyte portions. Male and female gametophytes look identical except when they produce reproductive structures. The female structure is called the archegonia and the male is the antheridia. |
| Links: |
| Liverworts |
| It is important
to remember that the part of the liverwort we see is in the gametophyte
(n) condition. As all other plants, as you will learn, liverworts undergo
an alteration of generations, meaning they move from gametophyte (n) conditions
to sporophyte (2n) conditions, etc. All liverworts live close to water,
like moss. This is because water is necessary for sperm to swim in for sexual
reproduction. This drastically limits the places liverworts (and mosses,
for that matter) can live in. Moss and Liverwort reproduction is very similar. However, some liverworts have coil-shaped cells to help disperse the spores, mosses do not have such cells. |
| Links: |
| http://www.hcs.ohio-state.edu/hcs300/liver1.htm |
Moss
Life Cycle |
| FYI: The dominant generation of moss is the gametophyte (n) condition. Mosses can have either separate male and female plants (60% of species), or have both sexes on the same plant (bisexual gametophytes, 40% of species). |
Male
and Female Development |
| 1) From the mature
sporophyte (2n) of the moss, spores (n) are produced via meiosis. They are
released and eventually undergo mitosis to produce protonema (small, green,
threadlike structures that resemble green algae). 2) The protonema continue to grow and differentiate, forming sexually mature gametophytes (n). Some will form female gametophytes (n) with an Archegonium, and some will form male gametophytes (n) with an Antheridium. The female (Archegonium) will produce and enclose and egg (n), and the male (Antheridium) will produce sperm (n). |
Fertilization
and Sporophyte Development |
| 1) Sperm from
the Antheridium will swim through water and into an Archegonium, to fertilize
the egg. This forms a zygote (2n). Remember that the Archegonium resides in the female gametophyte (n), and remains there, even during development. This means that the sporophyte (2n) stalk grows on TOP of the female gametophyte (n). 2) The zygote (2n) undergoes mitosis and develops into a sporophyte (2n) within the Archegonium. 3) As development continues, the sporophyte (2n) grows a long stalk that will emerge from the Archegonium. The base of the sporophyte stays attached to the female gametophyte (n). 4) A sporangium is present at the tip of this sporophytic stalk (2n). This sporangium produces spores via meiosis, which will be released and create new male and female gametophyte (n) mosses, which will start the life cycle over again.
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| ‹ Pterophyta › |
| Pterophyta is a group of vascular plants that do NOT have seeds, however they do have true leaves, roots and stems. No members of Pterophyta demonstrate major secondary growth (expansion in diameter). There are thousands of species within this phylum. |
| Links: |
| http://botit.botany.wisc.edu/courses/systematics/Phyla/Pterophyta/Pterophyta.html |
| Ferns |
| Most species of ferns are tropical (meaning they prefer high humidity environments), but they can be found pretty much anywhere except the driest places on Earth. For the average person, they are mainly used as ornamental plants, outside and inside. Most people aren’t aware how different they are compared to “normal” seed-producing plants, however. They have a fascinating life cycle, which includes alternation of generations (meaning they change from diploid to haploid, etc.). |
| Links: |
| http://www.hcs.ohio-state.edu/hcs300/svp2.htm |
Fern
Life Cycle |
| FYI: The dominant generation of ferns is the sporophyte (2n) condition. Unlike moss, the Antheridium and the Archegonium can be found on one fern, making them bisexual. |
Archegonium
and Antheridium Development |
| 1) If we look
at the underside of a reproductive fern leaf (from the mature sporophyte),
we will see spots called sori, which is a cluster of sporangia (2n). A mature
sporangium (2n) produces spores (n) by meiosis. These spores develop into
a small, heart-shaped gametophyte (n) via mitosis. The Archegonium and Antheridium
reside on the underside of this gametophyte (n). 2)
The Archegonium matures and holds the egg. The Antheridium matures and
produces the sperm. |
Fertilization
and Young Gametophyte/Sporophyte Development |
| Sperm (n) from
the Antheridium uses flagella to swim through water to an egg (n) in the
Archegonium and then proceeds to fertilize the egg, producing a zygote (2n).
A fertilized egg (2n) develops into a new sporophyte (2n), the leafy portion of the fern. The gametophyte (n) develops from the parent’s Archegonium. |
Mature
Gametophyte/Sporophyte Development |
| 1) The sporophyte
(2n) of the fern now produces sori on the underside of its leaves and eventually
releases spores. 2) These spores develop into small, heart-shaped gametophytes again and produce the Archegonium and Antheridium again to begin the life cycle over. |
updated 3-12-06