Chapter 15 : Kingdom Protista




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Chapter 15 : Kingdom Protista


Overview

After an introduction and summary of the features of members of the Kingdom Protoctista, this chapter discusses the divisions of algae. Initially, the Chrysophyta (yellow-green algae, golden-brown algae, diatoms, and cryptophytes) are discussed. Next, mention is made of the Division Pyrrophyta (dinoflagellates) and the role of members of the division in red tides and bioluminescence. For the Chlorophyta (green algae), asexual and sexual reproduction in Chlamydomonas, Ulothrix, Spirogyra, and Oedogonium are explored and mention is made of Chlorella, desmids, Acetabularia, Volvox, and Ulva. After a brief overview of the Euglenophyta (euglenoids), the Phaeophyta (brown algae) and Rhodophyta (red algae) are covered, with a discussion of the life cycle of a representative of each division being included. This is followed by a table summarizing divisional differences with respect to food reserves, special pigments, and flagella. The chapter concludes with a digest of the human and ecological relevance of some major algal phyla, and a brief discussion of slime molds and water molds .




Detailed Lecture Outline

I. Introduction

A. Oceanic Beginnings of Life

B. Transition to Land and Origin of Lignin

Coleochaete, a freshwater alga, ancestor of today’s land plants

II. Features of the Kingdom Protista

A. Eukaryotic Cells that do not fit into any other Kingdoms

1. Unicellular, colonial, filamentous, or multicellular

2. Lack a set of unifying features

B. Nutritional Mode

• photosynthetic, ingestive, or combination of both

C. Life Cycles Vary

• reproduction by cell division (asexual) and sexual processes

D. Taxonomic revisions likely to change organization of Kingdom Protista

III. Algae

IV. Phylum Chlorophyta—The Green Algae

A. Introduction

1. Comprise the largest of the algal divisions with about 7,500 species

2. Present in a wide variety of forms and habitats

a. The most common member in lichen "partnerships"

b. Important part of the plankton

3. Possess chlorophylls a and b

4. Believed to have been ancestral to the green plants

5. Carbohydrate food reserve is starch

6. The bryopsids have multinucleated cells

B. Chlamydomonas

1. General characteristics

a. Unicellular, about 25 µm long

b. With a pair of whip-like flagella

c. Single, cup-shaped chloroplast

• chloroplast contains one or two pyrenoids

2. Asexual reproduction

a. Flagella degenerate and fall off

b. Nucleus divides by mitosis

c. Sometimes as many as 32 cells may be produced within parent cell

3. Sexual reproduction

a. Under certain conditions, pairs of cells are attracted to each other and function as gametes

b. Protoplasts fuse to form zygote

c. Diploid protoplast undergoes meiosis, producing four haploid zoospores

C. Ulothrix

1. General characteristics

a. Each alga consists of a single row of cells forming a filament

b. Basal cell functions as a holdfast

c. Nucleus is surrounded by the chloroplast, which contains one or more pyrenoids

2. Asexual reproduction

a. Protoplast of any cell but holdfast can clump, undergo mitosis, and give rise to zoospores

b. Protoplasts that do not produce flagella are aplanospores

3. Sexual reproduction

a. As in asexual reproduction, zoospores are produced, but they act as gametes

b. Zygotes formed which produce thick walls and become dormant

D. Spirogyra

1. General characteristics

a. Form unbranched filaments of cylindrical cells

b. Chloroplasts are long and ribbon-shaped

2. Asexual reproduction

a. Do not form zoospores

b. Any cell capable of division

c. New filaments form by fragmentation

3. Sexual reproduction

a. Adjacent filaments form papillae which fuse to form conjugation tubes

b. Condensed protoplasts function as gametes

c. Zygotes develop thick walls and remain dormant, often over the winter

d. Protoplasts undergo meiosis, producing four haploid cells E. Oedogonium

1. General characteristics

a. An epiphyte

b. Terminal cell of each filament is rounded

c. Chloroplast large and net-like

2. Asexual reproduction

a. Akinetes occasionally formed

b. Usually zoospores produced singly at tips of filaments

c. Each zoospore has about 120 small flagella forming a fringe

3. Sexual reproduction (oogamy)

a. Short antheridia are formed in the filaments

b. Pair of sperms produced in each antheridium

c. Oogonia, swollen roundish cells, each contain a single egg

d. As egg matures, a pore develops on the side of the oogonium

e. A sperm enters the pore and unites with the egg to form a zygote

f. Zygotes may become dormant, but each will produce four zoospores by meiosis

F. Other Green Algae

1. Chlorella

• used in investigations of photosynthesis and respiration

2. Desmids

3. Hydrodictyon (water nets)

4. Acetabularia (mermaid's wine glass)

• used in experiments demonstrating influence of nucleus on cell form

5. Volvox

• colonial

6. Ulva (sea lettuce)

• exhibits haploid and diploid blades

7. Cladophora

V. Phylum Chromophyta—The Yellow-Green Algae, Golden-Brown Algae, Diatoms, and Brown Algae

A. Classification

1. Xanthophyceae—yellow-green algae

2. Chrysophyceae—golden-brown algae

3. Bacillariophyceae—diatoms

4. Phaeophyceae—brown algae

B. Yellow-Green Algae (Xanthophyceae)

C. Golden-Brown Algae (Chrysophyceae)

D. Diatoms (Bacillariophyceae)

1. Best known and economically most important chrysophytes

2. Cell walls contain silica deposited in an organic framework

3. Chloroplasts

a. Contain chlorophylls a, c1, and c2

b. Fucoxanthin (brownish pigment)

4. Food reserve is chrysolaminarin, a carbohydrate

5. Reproduction is unique

a. After diploid protoplast undergoes mitosis and division, a new half wall fitting inside the old half is formed

b. Eventually the protoplast undergoes meiosis, producing four gametes

c. Gametes fuse to form auxospores which grow rapidly before the cell walls are formed

E. Brown Algae—(Phaeophyceae)

1. Most species are relatively large; none are unicellular or colonial

2. Majority of genera are marine

3. Body differentiated into holdfast, stipe, and blades

4. Chloroplasts

a. Chlorophylls a and c

b. Fucoxanthin (brownish pigment)

5. Carbohydrate food reserve is laminarin

6. Cell walls contain algin (alginic acid)

7. Sargassum plentiful in tropical waters near Bermuda

• Sargasso Sea named because this alga thrives in these warm waters

8. Fucus—the common rockweed

a. Has separate male and female thalli

b. Puffy fertile areas (receptacles) develop at the tips of the thalli

c. Receptacles have pores leading to hollow chambers called conceptacles

d. Gametangia formed in conceptacles

1) Eight eggs produced in each oogonium

2) 64 sperm produced in each antheridium

VI. Phylum Rhodophyta—The Red Algae

A. Characteristics

1. Tend to occur in warmer and deeper waters than the brown algae

2. Most are filamentous

3. Life cycles complex

• meiosis occurs in a thallus called a tetrasporophyte

B. Reproduction in Polysiphonia

1. Three types of thalli all resemble each other

2. Spermatangia attached to male gametophyte thallus

• functions as a non-motile male gamete or spermatium

3. Carpogonia produced on female gametophyte thallus

a. Each carpogonium consists of a single cell

• bottle-shaped cell with long neck called the trichogyne

b. A single nucleus at the base of the carpogonium functions as the egg

4. Zygote develops into cluster of carposporangia toward the base of the carpocyst

a. Carpospores (diploid asexual spores) are produced

b. When settled in an appropriate location, carpospore germinates and develops into a tetrasporophyte

1) Tetrasporangia form along branches of the tetrasporophyte

2) Each tetrasporangium undergoes meiosis, giving rise to four haploid tetraspores

3) When tetraspores germinate, they give rise to male or female gametophytes

C. Other Features

1. Red to purplish colors due to phycobilins

2. Chloroplasts contain chlorophylls a and sometimes d

3. Carbohydrate food reserve is floridean starch

4. A number of red algae produce agar

VII. Phylum Euglenophyta—The Euglenoids

A. Characteristics

1. Many found in blooms in barnyard pools and sewage treatment ponds

2. Euglena is common example

a. Spindle-shaped with no rigid cell wall

b. Contains a pellicle, a type of modified cell wall lacking cellulose

c. Two flagella, one long, one very short (located within a reservoir)

d. Gullet present for ingesting food

e. Carbohydrate food reserve is paramylon

f. Some species can live without chloroplasts in a suitable environment

B. Reproduction

• Reproduction is by cell division

VIII. Phylum Dinophyta—The Dinoflagellates

A. Characteristics

1. Responsible for red tides

2. Plates of cellulose located just inside the plasma membrane

3. Possess two flagella

4. Chloroplasts

• contain chlorophylls a and c2

5. Many species are nonphotosynthetic

6. Some have an eyespot

7. Chromosomes remain condensed, contain large amount of DNA

8. Carbohydrate food reserve is starch

9. A few, such as those producing the red tide, produce toxins

10. Some are bioluminescent

B. Reproduction

• Reproduction by cell division; sexual reproduction rare

IX. Phylum Cryptophyta—The Cryptomonads

X. Phylum Prymnesiophyta (Haptophyta)—The Haptophytes

XI. Phylum Charophyta—The Stoneworts

XII. Human and Ecological Relevance of the Algae

A. Diatoms

1. Filtration

• sugar refining and swimming pools

2. Polishes

a. Silver and other metal polishes

b. Toothpaste polishes

3. Reflective signs

4. Insulation

• around blast furnaces and boilers

B. Other Algae

Chlorella, important protein source

C. Algin

1. Ability to regulate water behavior in a number of products

2. Thickening agent

• pastry fillings, gravies, flavored syrups

3. Emulsifier and suspension agent

• salad dressings and barbecue sauces

4. Stabilizer

• chocolate drinks, ice cream, coffee creamers

5. Paper coating

• inks adhere better to paper

6. Pharmaceuticals and cosmetics

• binder in pills, cough syrups

7. Brewing

• creamier beer foam with smaller, longer-lasting bubbles

D. Minerals and Food

1. Kelps contain a high concentration of iodine

2. Kelps can be used as fertilizers

• high content of nitrogen and potassium

3. Dulse, purple laver, and Irish moss used as food

4. Carrageenan used as a thickening agent

5. Funori is used as laundry starch or adhesive in hair dressings

E. Agar


1. Produced most abundantly by the red alga Gelidium

2. Culture medium for bacterial growth

3. With added nutrients, can be used as culture medium for both plant and animal cells

XIII. Other Members of Kingdom Protista

XIV. Phylum Myxomycota—The Plasmodial Slime Molds

A. Habitat

• rotten leaves, tree bark

B. Shape


1. Plasmodium

2. Amoeboid movement

3. No cell walls

C. Reproduction

1. Plasmodial slime molds

a. When food supply dwindles, or environment changes, plasmodium converts into many separate sporangia, each with thousands of spores

b. As spore is formed, a single nucleus and a little cytoplasm is surrounded by a wall

c. Meiosis occurs, and three of the four nuclei degenerate

d. Spore germinates, and one or more myxamoebae emerge (called swarm cells if they have flagella)

e. Eventually the myxamoebae (or swarm cells) function as gametes

XV. Phylum Dictyosteliomycota—The Cellular Slime Molds

A. Characteristics

1. Do not produce plasmodia

2. When population reaches certain size, the amoeba-like cells stop feeding and form a pseudoplasmodium, which crawls like a slug

3. Pseudoplasmodium eventually is transformed into a sporangium-like mass of spores

B. Human and Ecological Relevance of the Slime Molds

1. Decomposers

• decomposition of organic matter

2. Disease Causing Agents

• several cause disease of cabbages, potatoes, and watercress

XVI. Phylum Oomycota—TheWater Molds

A. Habitat

1. Aquatic organic material

• cottony growths on fish, dead insects

2. Crop plants

• downy mildews of grapes, late blight of potato (Irish potato famine, 1846)

B. Shape

• hyphae coenocytic

C. Reproduction—Saprolegnia

1. Asexual

• formation of numerous biflagellated zoospores

2. Sexual

• involves oogonia and antheridia where meiosis occurs

D. Human and Ecological Relevance of the Water Molds

1. Downy mildew of grapes

• threatened French wine industry in 19th century

2. Late blight of potato

• caused Irish famine of 1846






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