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LAB 11 ALGAE AND FUNGI Kingdom Protista; Plant like protistans Algae is a term representing great diversity among simple aquatic organisms that are plantlike in the sense that they contain chlorophyll. Most are photosynthetic autotrophs, but some possess the ability to survive heterotropically. The protistan algae have no cell wall like higher plants while the more complex algae possess cellulose cell walls and represent the peak of plant diversity in water environments. Many possess between one and three flagella. These organisms clearly illustrate the difficulty with classifying everything as autotroph or heterotroph, or as plant or animal. For this reason the kingdom Protista is sometimes considered to be a collection of "misfits".
Remember that protists are eukaryotic organisms so that even the most simple unicellular protist is much more complex than the prokaryotes of the kingdom Monera. Algae is found in murky freshwater ponds and marine populations are a major component of phytoplankton. Most are unicellular although some colonial forms exist. All algae reproduce asexually but some of the complex algae exhibit sexual reproduction as well.
There are several phyla of algae in the kingdom Protista:
Phylum Chrysophyta: Golden Algae. Named for their golden color which results from the yellow and brown pigment they contain. Most are found in freshwater and are colonial. In ponds that freeze in winter or dry up in summer, they survive by forming resistant cysts, from which active cells emerge when conditions are favorable. They store surplus food as oil and are important contributors in the formation of petroleum deposits. [diatoms]
Phylum Euglenophyta: Mostly fresh water organisms lacking a cell wall. All possess chlorophyll and one to three flagella. Some members, like Euglena, when grown in the dark lose their green color and become heterotrophic by absorbing food substances through the cell surface.
Phylum Pyrrophyta: Fire Algae. Marine and fresh water with two flagella which produce a whirling movement. Like higher plants they have cell walls composed of cellulose and store food as starch. They are important members of phytoplankton (usually microscopic, autotrophic aquatic organisms) which form the foundation of the food chain. Responsible for the "red tides" which occur in warm waters as a result of occasional population explosions. [dinoflagellates]
Phylum Rhodophyta: Red Algae. Multicellular marine algae found in warmer waters. They contain calcium carbonate and are important in reef formation.
Phylum Phaeophyta: Brown Algae. Named for their dark brown color. Some are simple filamentous algae but others reach lengths of 100 meters. They provide food and habitat for marine organisms. [Fucus]
Phylum Chlorophyta: Green Algae. Diverse group showing all three life cycles. Members include single-cells, filamentous colonies, and multicellulr sheets. All possess chlorophylls a and b and cell walls of cellulose as do members of the plant kingdom. [Spirogyra]
Question 1: Are protistan algae heterotrophic or autotrophic?
Question 2: How are some protistan algae able to survive adverse environmental conditions?
Question 3: What is a red tide?
Question 4: Of what advantage is possession of flagella to aquatic organisms that are photosynthetic?
Question 5: What economic contribution results from the golden algae?
LAB OBJECTIVES:
1. To observe and learn characteristics of both living and preserved examples of the algae. 2. To observe and learn characteristics of representative examples of fungi.
I. Phylum Euglenophyta (U'glen-of"i-ta) - flagellated protistan algae
This is the smallest phyla of protistan algae and Euglena is the prototype organism. It is a common freshwater organism that is very versatile in its nutrition. When light is unavailable Euglena simply changes nutritional strategies and survives heterotrophically.
ACTIVITIES:
1. Prepare a temporary wet mount of Euglena on a clean slide. Euglena moves quickly and may be slowed down by mounting them in a drop of Protot-slo. Examine the slide under 10X. Notice the nucleus and the numerous chloroplasts. An eyespot near the base of the flagellum is labeled in figure 1. The eyespot is sensitive to light and permits movement by flagellum into or out of the light. Although the flagellum may not be visible, movement of the cell produced by the whip-like action of the flagellum is visible.
2. Examine a prepared slide of Euglena
under 40X. Most flagella remain unstained and are
3. Draw Euglena. Label the flagellum, eyespot, nucleus, and chloroplasts.
II. Phylum Chrysophyta (Kri'sof"i-ta) - golden protistan algae
An important member of the golden algae are the diatoms. Diatoms have a rigid cell wall impregnated with silica, a constituent of both sand and glass. The cell walls often display intricate patterns of pits and ridges which actually allow for exchange of gases and other substances between the cell and aquatic environment. The glasslike shells of these protistan algae consist of two halves that fit together like the bottom and top of a pillbox. The shape of the cell and its pattern of pores are distinctive enough to be used for classifying diatoms. These silica walls resist decay and as a result, they have accumulated on the ocean floor in enormous numbers. Deposits of this "diatomaceous earth" are mined and used commercially as an abrasive in silver polish and toothpaste and as packing in air and water filters.
Question 7: Describe the anatomy of a diatom.
Question 8: What characteristic of the diatoms make them commercially useful?
ACTIVITY:
1. Obtain a prepared slide of "Diatoms". Adjust the iris diaphragm to its lowest setting and examine the slide on 10X. Be patient...light passes through these organisms just as it would glass. Finding them may be a challenge, but one well worth the effort!
Question 9: Draw several diatoms.
III. Phylum Rhodophyta (Ro'dof"i-ta) - red algae
The red algae are almost exclusively marine plants, most abundant in the warmer ocean waters and as a rule growing more deeply submerged than the brown and green algae. Red algae are small, fragile, delicate plants, rarely more than 0.7 meter long. They look like feathery, or lacy tufts of plants. Most of the species are filamentous. They have complex life cycles which we will not consider.
In some, known as corallines, the plants are heavily impregnated with limestone and are considered to be just as important to the formation of coral reefs and atolls as coral animals.
Red algae provide several useful products. For example, a gelatinous cell wall material provides agar, which is used extensively in laboratories for the culture of bacteria and fungi and some higher plants. Carrageenin, another colloidal substance, is used as an emulsifying agent in dairy products such as chocolate milk, where it prevents the chocolate from settling out.
The red alga Porphyra is used as food in several oriental dishes. In one, called "sushi," various meats and rice are wrapped in sheets of the alga.
Question 10: In what type of environment do most red algae grow?
Question 11: Describe the structure (physical appearance) of red algae.
Question 12: List several reasons why the red algae are important.
ACTIVITY:
1. Examine the various preserved examples of red algae available.
IV. Phylum Phaeophyta (Fe'of"i-ta) - brown algae
The brown algae are almost exclusively marine plants, most abundant along the rocky shores of cooler seas. The dark color is due to a brown pigment, fucoxanthin. Chlorophyll and related pigments are present, but their color is masked by the fucoxanthin. The largest algal forms in the world are found among the Phaeophyta. The larger forms, commonly called kelps, contain commercially important amounts of iodine, potassium, and sodium. Processed in various ways, the kelps are utilized for the source of algin (sodium alginate) from brown algae in the manufacture of ice cream, salad dressings, cake icings, chocolate milk, shaving creams, face and hand lotions, jellies, cosmetics, many pharmaceutical products, candies, sizings for industrial purposes, and many other products. Some agar is obtained from the brown algae, but the best grade comes from the red algae.
Question 13: What is the brown pigment of phylum Phaeophyta?
Question 14: What is kelp?
Question 15: List several commercial uses of the brown algae.
ACTIVITIES:
1. Examine the broad, flat seaweed known as Fucus (rockweed). Note the swollen tips of the structure and the dichotomous (branches in two's) structure. The body of this seaweed is called a thallus (means flat). Air bladders are located within the thallus. The swollen structures at the thallus tips are receptacles where sex organs are located.
Question 16: What is a thallus? (Refer to figure 2.)
Question 17: What is a receptacle? (Refer to figure 2.)
2. Examine Sargassum, a floating brown alga in tropical waters. Note its stem-like stipe, leaf-like blades, and berrylike air bladders. These plants float in large numbers, often extending for hundreds and thousands of hectares (10,000 square meters) over the sea's surface. The ships of Christopher Columbus sailed right into one such area, much to the crew's dismay. They feared their ships would be dragged under by it. The Sargasso Sea is named after these plants.
Question 18: Where is Sargassum found?
V. Phylum Chlorophyta (Klo'rof"i-ta) - green algae
The green algae range from single motile cells to broad, sheet-like forms. The most common body plan is a series of straight or branched filaments.
One group of green algae represents an evolutionary line that is thought to have given rise to the first land plants. Existing species are mostly freshwater organisms; some even live on moist land!
ACTIVITY:
1. Examine living material of Spirogyra (pond scum) and prepared slides of Spirogyra conjugation. Spirogyra is usually found in clear, cool, running water. The filaments have a characteristic slippery feel to the touch. A cylindrical cell contains one or more (depending on the species) spirally-shaped chloroplasts, each with several pyrenoids (sites of starch synthesis). Sexual reproduction is by means of non-motile isogametes. During sexual reproduction two apparently identical filaments (designated as + and -) move to become placed side by side. Tubes push out from each filament, meet, fuse, and form a short connecting passageway between the two cells. The contents of one cell (isogamete) move through this conjugation tube into the cell of the adjacent filament, fusing with its contents to form a zygote. This process is called conjugation. When the zygote germinates, it gives rise directly to a new filament. The prepared slides show the zygotes or zygospores of Spirogyra. Refer to figure 3.
Draw a living Spirogyra filament. Label the nucleus and chloroplast.
Draw a Spirogyra zygospore.
Question 19: What is a pyrenoid?
Question 20: Is the zygote haploid (1N) or diploid (2N)?
Question 21: What is conjugation? Fungi
The fungi include organisms such as the molds, mildews, mushrooms, puffballs, smuts, rusts, shelf or bracket fungi, and many parasitic species which cause infections such as yeast infections, athlete's feet, jock itch, and ring worm. None possesses chlorophyll, and thus they are dependent on other organisms for their food. Some are saprophytes (fungi that derive their energy from non-living organic matter); others are parasites (fungi that live at the expense of their host organisms); and still others may be mutualistic symbionts (organisms that coexist with other organisms in a mutually beneficial relationship). Lichens are compound organisms consisting of two components, a fungus and an alga; these organisms are mutually beneficial.
Fungi are very numerous and include a great variety of forms. Some are commercially valuable, for instance, yeast in the preparation of bread and the production of industrial alcohol by fermentation.
The fungi, however, cause most of the plant diseases with accompanying losses amounting to millions of dollars annually. In addition, millions of bushels of fruits and vegetables in storage are ruined yearly by fungi. Some serious human diseases are caused by fungi.
The fruiting (reproductive) body is the conspicuous part of most fungi and is important in the classification of these organisms. The vegetative (assimilative) body is usually hidden from view under leaves, in the soil, under bark, or within the plant it is living upon. The entire vegetative body is the mycelium (mycelia, plural) of the fungus. Each individual strand of the mycelium is a hypha (hyphae, plural).
There are several divisions in the kingdom Fungi. In some classification schemes, this taxon is designated phylum rather than division.
Division Oomycota: Mostly aquatic organisms that have motile cells at specific stages of their life cycle. Cell walls composed of polymers of glucose, including cellulose (water molds).
Division Zygomycota: Terrestrial fungi with hyphae that develop septa (cross walls) during formation of reproductive structures. Chitin is the predominant component of the cell walls (black bread mold).
Division Ascomycota: Terrestrial and aquatic fungi. Hyphae have perforated septa; complete septa cut off reproductive structures. Chitin in cell walls. Sexual reproduction involves formation of a saclike ascus in which meiosis precedes spore formation (yeasts, powdery mildews, morels, and truffles).
Division Basidiomycota: Terrestrial fungi. Hyphae have perforated septa; complete septa cut off reproductive structures. Sexual reproduction involves formation of basidia in which meiosis takes place and on which the spores are borne (mushrooms and rusts).
Division Deuteromycota: Consists mainly of fungi that have characteristics of the ascomycetes in which sexual reproduction has not been observed. These organisms are generally classified on the basis of their asexual spore-bearing structures. Includes fungi that cause athlete's foot and other skin diseases and many of the molds that flavor cheeses (e.g., Camembert and Roquefort).
In this exercise, we will only study Zygomycetes, Ascomycetes, and Basidiomycetes.
Question 22: Define the difference between saprophyte, parasite and mutualistic symbiont.
Question 23: Why are fungi important? (Include both positive and negative importance.)
Question 24: What is the basis for classification of most fungi?
Question 25: What is the difference between hypha and mycelium?
VI. Division Zygomycota (Zi-go'mi-ko"ta) - zygote fungi A zygomycete, Rhizopus nigricans or black bread mold, is widely distributed over the world, being readily spread from place to place by means of light, airborne spores. Rhizopus has been commonly called bread mold because it grows well on bread. Rhizopus also grows well on fruits and vegetables, and a number of damaging rots are due to this fungus. Some rots due to Rhizopus are the soft rot of sweet potatoes, watery rot of strawberries, storage or transportation rot of apples, and soft rot of tomatoes. Germinating seeds or seedlings may also be attacked by this fungus.
Rhizopus demonstrates both asexual and sexual reproduction. Asexual reproduction is by the formation of sporangiospores. Sexual reproduction is by conjugation (exchange of genetic material), a process similar to the filamentous green alga Spirogyra.
ACTIVITY:
1. Obtain a slide of Rhizopus. Both asexual and sexual reproductive structures will be found on a single slide.
Question 26: Where is Rhizopus found?
Question 27: Using the labeled diagrams in figure 4, locate and identify the following:
sporangium, sporangiophore, stolon,
rhizoid. The zygospore (zygote) is apparent
Question 28: How does Rhizopus reproduce?
VII. Division Ascomycota (As-ko'mi-ko"ta) - sac fungi
The ascomycetes are called the sac fungi because of a reproductive structure, the ascus, that has the appearance of an elongate sac containing eight ascospores. The most obvious part of an ascomycetes fungus is its fruiting body (spore-producing body), the ascocarp. The fruiting body appears above ground or above the surface on which the fungus is growing and often gives the fungus its common name. The fruiting body of Peziza is cup-shaped and is composed of many thousands of hyphae. The inner surface of the cup is called the hymenial layer or fertile layer, and this layer is composed of hyphae the tips of which have formed asci (plural of ascus) with eight ascospores in them. These spores would have been released to create more mycelia. Asexual reproduction in the ascomycetes is accomplished simply by budding of asexual spores from the tips of some of the hyphae. These spores are called conidia.
ACTIVITIES:
1. Obtain a slide of Peziza. Using figure 5, identify 8 ascospores inside an ascus.
2. Mount on a slide a drop of material from a 10 percent glucose solution to which a portion of moist yeast has been added and thoroughly mixed a few hours previously. Cover with a coverslip and examine under 40X. Look at the form, size, color, and content of the yeast cells. Some cells are producing buds. Refer to figure 6.
Common baker's yeast which is used in making breads, cakes, etc. is a "unicellular" ascomycete. The yeast cells ferment the sugar in the dough, and escaping carbon dioxide causes the dough to rise.
VIII. Division Basidiomycota (Ba-sid-i-o'mi-ko"ta) - club fungi
The basidiomycetes represent another large and varied group of fungi that have both saprophytic and parasitic members. They are characterized by having a basidium (a club-shaped structure on which are usually produced four spores called basidiospores) formed at some point in the life cycle.
Question 29: What is a basidium?
A. Mushrooms
Mushrooms are characterized by plates or gills on the undersurface of a fruiting body. The basidia extend from the free surface of the gills. Refer to figure 7.
Figure 8: Detail of gill structure, a Basidiomycete
The mushroom mycelia grow beneath the surface of their substrate. When haploid mycelia of different strains unite, another mycelium is formed that is diploid. This mycelium may produce a fruiting body, commonly called a mushroom, which consists of a stalk and cap.
ACTIVITIES:
1. Examine the fruiting body of Agaricus campestris, the common commercial mushroom. Note the stalk and cap. Examine the undersurface of the cap and locate the gills. If the mushroom is young, the gills may be covered by a thin membrane that extends from the stalk to the outer margin of the cap.
2. Examine a prepared slide of Coprinus, showing a cross section through the cap. Identify gills, basidia, and basidiospores. Refer to figure 8.
B. Bracket Fungi
The bracket (shelf) fungi are parasitic or saprophytic on various trees. The mycelium of the fungus may grow within the trunk several years before forming the characteristic woody fruiting body on the outside of the tree.
ACTIVITY:
1. Examine several bracket fungi, and note the several growth layers that are evident.
Question 30: How could these growth layers be used to estimate the age of a bracket fungus?
IX. Lichens
The alga in this organism is usually a green alga, while the fungus is usually an ascomycete (blue-green mold or cup fungus). The alga, through photosynthesis, furnishes the food, while the fungus apparently supplies chemical substances that promote the alga's growth and also helps to retain moisture, at least during part of the year, for the alga's needs. See figure 9a. On the basis of growth habit, lichens are grouped into crustose (forming a fine crusty growth), foliose (forming a somewhat leaflike mat), and fruticose (having "shrubby" growth) species.
Question 31: What is a lichen?
Question 32: List and briefly describe three types of lichens on the basis of growth habit.
ACTIVITY:
1. Examine species of lichens which show the crustose, foliose and fruticose growth forms. Refer to figure 9b & 9c.
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