Exercise Fungi Worksheet PDF

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The largest living organism on the planet is hundreds of tons in weight, covers an area greater than 1,800 football fields, and is THOUSANDS of years old. No whale or redwood tree can compare. This organism is a Basidiomycete fungus. Fungi are not as easily distinguishable as many plants, and their domain is primarily out of sight below ground. For these reasons, they are often brushed aside as unimportant or nuisances, rather than appreciated as the diverse and highly successful organisms that they are. To understand fungi, it is important to think about their role in the ecosystem, and what makes them so successful. Unlike plants, fungi are heterotrophic, obtaining energy by ingesting existing macromolecules- often dead and decaying, but occasionally living matter as well. Differences among the five phyla of fungi are subtle, but represent adaptations to grow, reproduce, and disperse. In this lab, we will explore the five most common phyla of fungi, with an emphasis on the reproductive cycles that largely differentiate the groups. To bring these dark-loving organisms into our light, we will also consider an example of how each phylum has had a profound influence on another more familiar branch of life. You already know of some important fungi – mushrooms, yeast, and mold, for example. Now let’s see what differentiates these fungi, and how they fit into the greater ecosystem.

Phylum Chytridiomycota (kī- ˌtri-dē-ō-mī- ˈkō-tə) The original fungus, chytrids diverged from their ancestors- flagellated protists- over a billion years ago. The presence of flagella (a slender threadlike structure, especially a microscopic whiplike appendage that enables many protozoa, bacteria, spermatozoa, etc., to swim) on chytrid spores suggests that these are the most primitive fungi, since all other fungi are non-flagellated. Parasitic chytrid fungi have contributed to the worldwide decline in amphibian populations. 1) On the following evolutionary tree, mark the point at which fungi evolved spores without flagella. Protista

Chytridio

Zygo Glomero

Asco Basidio

2) The presence of flagella suggests that chytrids live in what type of environment? The presence of flagella suggests that chytrids live in aquatic environment.

3) As the most primitive fungi that were the first to diverge from the protists, do you think chytrids are unicellular or multicellular organisms? Why? Chytrids are the simplest and most primitive of the true fungi (Eumycota). The common ancestor for chytrids diverged from the protist lineage almost 500 million years ago (late pre-Cambrian period). Since most protists are unicellular, the common ancestor for chytrids are considered to be unicellular. most chytrids described so far are true to this trend and are unicellular. However as in the case of protists, very rare cases pseuo-multicullar organisms exist within the chytrid lineage, with a few forming aseptate hyphae with multiple nuclei. So evolutionary, the chytrids arose before multicellularity evolved in fungi.

4) Observe the Allomyces sporophyte slide. Draw what you see and label the sporangia and flagella.

Phylum Zygomycota Zygomycetes are recognizable as molds appearing on bread, fruit, and other foods when they’ve been left out in moist conditions for too long. They were the first multicellular fungi to evolve a network of cells known as hyphae. A mass of hyphae from a single

individual is known as a mycelium. Hyphae networks are often strings of single haploid cells with walls made of chitin which absorb and digest nutrients from their surroundings. These cells are sometimes unseparated, so cytoplasmic fluids are able to flow freely throughout the cells of the hyphae. This allows zygomycetes to grow and spread very quickly.

5) Observe the 3 Rhizopus slides. Sketch and label the hyphae, sporangia, and spores. What is the difference between each of the three slides? The differences between each of the three slides is that some of the Rhizopus does not have sporangia nor hyphae, but all of them have spores.

6) Why might it be important for zygomycetes to grow and spread quickly? What are they competing for? What are they competing with? Zygomycetes are a paraphyletic group of fungi that thrive in soil, or on dead and decaying plant and animal matter. They draw their name from their method of sexual reproduction, which leads to the production of zygosporangia and zygospores. Zygomycetes also bear sporangia, which are compartments in which asexual spores are formed. This helps them to colonize new substrates quickly and efficiently. They are competing for the same resources with members of the larger fungal phylum Dikarya (division Ascomycota and Basidiomycota). However, zygomycetes have a competitive edge in the fact that they can extend their aseptate hyphae (coenocytic) much quicker than their cousins (the so-called “higher fungi”) who posses septate hyphae, making them relatively slower growers. Furthermore, zygomycetes are much more adapt at digesting and assimilating decaying animal and fungal matter than members of Dikarya as they carry potent enzymes that can digest proteins and chitin.

7) Hyphae have a very high surface area to volume ratio, meaning there is not a lot of space inside the hyphae that is far from the hyphae walls. What are the possible advantages of hyphae having a large surface area? (consider the function of hyphae) The increased surface of hyphae ensures greater exposure of the organism to the environment and ensures effective & maximal absorption of food from the surroundings. The diffusion reate inside the hyphae will also be fast.

8) At what point in the sexual reproductive cycle do haploid hyphal cells fuse together? (See Reproductive Cycle slide). What characteristics do these new cells have? Sexual Reproduction involves the combination of two sets of chromosomes via the fusing of two nuclei, each of which contains one set of chromosomes. A nuclei with one set of chromosomes is called a haploid nucleus, the haploid nuclei are contained in cells of some sort and naturally a cell with a haploid nucleus is called a haploid cell. The first step towards the fusion of nuclei is the fusion of two haploid cells and this step is called plasmogamy. After plasmogamy the two nuclei meet and fuse, a process called Karyogamy, and this yield diploid nucleus, namely one with two sets of chromosomes. Plasmogamy creates a heterokaryotic zygosporangium that has multiple haploid nuclei from parents and has a rough durable coating.

9) What is a possible benefit of the asexual reproductive cycle? What is a possible detriment of this cycle (why is sexual reproduction beneficial)? The possible benefit of the asexual reproductive cycle is able to reproduce without a partner and the possible detriment of this cycle is unable to increase genetic diversity. Sexual reproduction can be beneficial because it results in an increase in genetic diversity.

Phylum Glomeromycota Glomeromycetes form a relatively small phylum of just 150 species. However, they are among the most important of all fungi, as they form obligate symbiotic relationships (meaning they cannot exist in isolation) with the majority of land plant species. They reproduce asexually by forming large spores filled with hundreds of nuclei and, if

germination is unsuccessful, often retract into the spore until external conditions improve.

10) Glomeromycota grow specialized hyphae called haustoria (see slide). What is their function? Describe situations in which this could be both helpful and harmful to a plant. Their function of haustoria is penetrate the host plant's cell wall and siphon nutrients from the space between the cell wall and plasma membrane but do not penetrate the membrane itself. This could be both helpful and harmful to a plant if they are giving nutrients as well as taking .

11) Plants probably existed in beneficial relationships with fungi from the earliest periods of colonization of land. What essential roles did these fungi serve? Think about the earliest land plants, and their limitations. How could fungi help? Earth first plant began to colonies the land over 470 million years ago by forming symbiotic relationship with soil fungi. The plants grow and reproduce better where colonies by symbiotic fungi because fungi provide essential soil nutrients without them to breakdown detritus. It would be difficult for photosynthetic organisms to extract anything from the ground, in return the fungi also benefit by receiving carbon from the plants. An ancient plant like liverworts associate with early diverging arbuscular mycorrhizal fungi which makes the insoluble phosphate into soluble form for better absorption by the plants. Its colonies early diverging liverworts at least 10 times more common than in flowering plants.

12) Sketch a diagram of a plant in association with Glomeromycota mycorrhizae. Label the exchange of resources from fungi to plant and plant to fungi.

13)

Observe the mycorrhizae slide. Draw what you see and label the haustoria and

hyphae.

Phylum Ascomycota The most diverse phylum of fungi, ascomycetes are found in marine, freshwater, and terrestrial habitats. Spores are produced in sac-like asci, hence the reference to “sac fungi” when people speak of this phylum. The yeast Saccharomyces cerevisiae, important for brewing beer and for genetic research, is part of phylum Ascomycota. There are other well-known ascomycetes that help cure infection (Penicillium chrysogenum), cause ringworm (Tinea corporis), and produce the sickening black mold (Stachybotrys chartarum) that was experienced in many homes after Hurricane Katrina.

14)

Plasmogamy occurs when two conidia of opposite mating type

(essentially gender) fuse together, and results in the formation of a dikaryotic ascus. 15)

What does it mean to be dikaryotic?

Dikaryotic means having two unfused haploid nuclei. In some species of fungi, the nuclei pair off two to a cell and one from each parent.

16) What is the importance of karyogamy? Why can the nuclei not remain separate? Karyogamy is essentially sexual reproduction, allowing for genetic diversity and resulting in a diploid nucleus. The nuclei can not remain sperate because of the role this stage plays in the life cycle.

17) What do you think the suffix gamy, as in karyogamy and plasmogamy, means? The suffix -gamy, as in karyogamy (the fusion of the nuclei of cells) and plasmogamy (fusion of the cytoplasm of two or more cells), means union or reproduction.

18) Observe the 2 Penicillium images and the 2 Aspergillus Ascomycete microscope images. Considering what you know about spores, how do you think dispersal occurs? What kinds of adaptations might aid in spore dispersal? (Not necessarily limited to Ascomycota). Draw what you see and label conidia and conidiaphores.

Dispersal occurs in the Ascomycota. The spore dispersal starts by releasing/discharge spores and from the parent dispersal away. In most species, fruiting bodies are produced that bear ascospores.

19) Observe the Peziza median asci slide and draw below. What is the role of the ascus in the Ascomycete life cycle?

The ascus is a sac in which karyogamy occurs resulting in a diploid cell that then undergoes meiosis to create haploid cells which develop into spores and when mature the ascus bursts dispersing the spores.

20) Describe three important examples of Ascomycetes affecting human life or human interests. Penicillin (antibiotic medicine), yeast (brewing, baking, scientific research), truffles and morels (economically important food), black mold (toxic).

Phylum Basidiomycota Basidiomycota are a group of about 30,000 species and include mushrooms, puffballs, and shelf fungus. Out of all the fungi, basidiomycota are the best at decomposing the complex lignins found in wood and as such they are commonly found on stumps, decaying trees, and rotting logs. While most people are familiar with these basidiocarps (fruiting bodies) most of the organism lives below ground. These basidiocarps are composed of a cap with gills underneath, these gills can have a surface area of 200 square centimeters and can drop a billion basidiospores! 21)

Compare the life cycles of Ascomycota and Basidiomycota. Both

organisms have very similar life cycles with a significant portion of their lives spent as haploid mycelium (haploid or diploid?). In the life cycle of Ascomycota, conidiospores germinate into mycelium. The male sexual organ is called antheridium and female is known as ascogonium in mycelia. Sexual reproduction takes place and for ascocarp and further to ascocarp. Zygote formation is followed by the meiosis which forms four haploid nuclei. Now, via mitosis and cell division, 8 ascospores are generated. Each will disperse and germinated to a new ascomycete. In the life cycle of Basidiomycota, it follows only sexual reproduction in which spores are germinated to form mycelia. Further plasmogamy and mitosis occur which form basidiocarp. Karyogamy results in the formation of four basidium and then each basidium will modified into basidiospores and they disperse in the environment for another germination cycle.

22)

Observe the Coprinus slides, and sketch below. Basidiomycota

produce 4 (# of) basidiospores on their basidium/basidia (structure).

23) Observe the slides of the dissection of the button mushroom. Draw and label the pileus (cap), gills, stipe (stalk), and the annulus (ring around the upper end of the stipe). Note that the gills are composed of

individual basidia.

Lichens Lichens are not individual organisms, they are symbiotic associations between a photosynthetic microorganism and a fungus, in which millions of photosynthetic cells are held in a mass of fungal hyphae.

24) be?

What do you think these “photosynthetic microorganisms” might

“Photosynthetic microorganisms” can be with either algae or cyanobacteria. They can also contribute more oxygen to the atmosphere than plants. About 70-80% of atmospheric oxygen is contributed by photosynthetic phytoplankton, algae, and cyanobacteria.

25) Observe the lichen specimens and draw below. Label which is foliose (leaflike), fruticose (shrublike), and crustose (encrusting).

26) Observe the lichen microscope images, sketch the basic interaction of the two components of the lichen, and label the exchange of resources from one to another.

27) There are over 17,000 “species” of described lichens. What characteristics of lichens might enable such diversity? The characteristics of lichens that might enable such diversity are rather self-sufficient; the ascomycete fungus provides moisture, structure, and nutrients, and the algae or cyanobacteria photosynthesize energy. It allows lichens to grow in a multitude of habitats including bare rocks.

28) Lichens are often found in harsh habitats that may not be suitable for other life forms. In such habitats, they aid in the establishment of plants by decomposing rock into soil and harnessing water. What are the roles of the algal and fungal components of lichens in this process? The roles of the algal components of lichens are photosynthesized to provide energy/food. It prepares for the fungi. The algal component is known as phycobiont. The roles of fungal components of lichens are decompose substrate, collect soil, and provide structure & moisture. The fungal component is known as mycobiont, which are autotrophic and heterotrophic. Fungi provide shelter and absorb mineral nutrients and water for its partner....