SECTION 27-1 OVERVIEW OF ALGAE
Algae are plant-like organisms that belong to the Kingdom Protista. Although most species of algae are unicellular, some are large, multicellular organisms. Algae differ from protozoa, which are also classified in the Kingdom Protista, in that they manufacture their food through the process of photosynthesis.
OBJECTIVES: Compare algae with other protists. Explain how algae differ from plants. Describe the various body structures of algae. Identify the characteristics used to classify algae into seven phyla. Summarize the events of asexual and sexual reproduction in representative genera of algae.
CHARACTERISTICS
1. Algae are a diverse group of protists. They range in size from microscopic Single-celled organisms to large Seaweeds that may be hundreds of feet long.
2. Algae are AUTOTROPHIC Protists- they are called Plant-like because they perform PHOTOSYNTHESIS. Like plants, Algae contain CHLOROPHYLL and produce their own Carbohydrates giving off Oxygen as a by-product of Photosynthesis.
3. Algae are Different from Plants Because they LACK Tissue Differentiation and have No True Roots, Leaves or Stems.
4. The Reproductive Structures of Algae also Differ from those of plants; they form Gametes in Single- Celled GAMETANGIA, or Gamete Chambers. Plants form Gametes in Multicellular Gametangia.
5. For these Reasons Algae are classified as Protists.
6. Despite their Diversity, different kinds of algae have Some things in Common.
A. Most Algae are AQUATIC.
B. Most have FLAGELLA at some point in their
life cycle.
C. Algae Cells often contain PYRENOIDS,
organelles that Synthesize and Store Starch.
STRUCTURE
1. The Body Portion of an Algae is called a THALLUS. The Thallus of an Algae is usually Haploid.
2. A variety of Thallus formats characterize Algae. The Thallus can consists of a Single Cell, or made up of Many Cells in varying arrangement.
3. FOUR Types of Algae are recognized, based on the following Body Structures: UNICELLULAR, COLONIAL, FILAMENTOUS, AND MULTICELLULAR. (Figure 27-1)
A. UNICELLULAR ALGAE - A Structure that consists of a Single Cell,
most are Aquatic Organisms, and form the PHYTOPLANKTON, a
population of photosynthetic organisms the forms the foundation of the Food
Chain. They produce half of the worlds Carbohydrates and are among the
major producers of Oxygen in the Atmosphere. (Figure 27-1 (a))
B. COLONIAL ALGAE - Have a Structure that consists of Groups of
Cells acting in a coordinated manner. Some of these Cells Become Specialized.
This division of Labor allows Colonial algae to move, feed, and reproduce
efficiently. (Figure 27-1 (b))
C. FILAMENTOUS ALGAE- Have a slender, rod-shaped Thallus, composed
of rows of cells joined end to end. Some have specialized structures (Holdfast)
that Anchor the Thallus to the ocean bottom. This adaptation secures the
Alga in one place as it grows toward the sunlight at the water's surface.
(Figure 27-1 (c))
D. MULTICELLULAR ALGAE - Have a large, complex Thallus. The
Leaf-like Thallus may be several centimeters wide but only TWO Cells Thick.
Some have rubbery leaflike portions, stem-like regions, and enlarged air
bladders (Figure 27-1 (d))
CLASSIFICATION
1. Algae are classified into Seven Phyla, based on their Color, Type of
Chlorophyll, Form of Food Storage Substance, and Cell Wall Composition.
(Table 27-1)
| PHYUM | THALUS FORMAT | PHOTOSYNTHETIC PIGMENTS | FORM OF FOOD STORAGE | CELL WALL COMPOSITION |
| Chlorophyta (Green Algae) |
Unicellular, Colonial, Filamentous, and Multicellular | Chlorophylls a and b, Carotenoids | Starch | Polysaccharides, Primarily Cellulose |
| Phaeophyta (Brown Algae) |
Multicellular | Chlorophylls a and c, Carotenoids, Fucoxanthin | Laminarin (an oily carbohydrate) | Cellulose with Alginic Acid |
| Rhodophyta (Red Algae) |
Multicellular | Chlorophylls a, Phycobilins, Carotenoids | Starch | Cellulose or Pectin, many with Calcium Carbonate |
| Bacillariophyta (Diatoms) |
Mostly Unicellular, Some Colonial | Chlorophylls a and c, Carotenoids, Xanthophyll | Leucosin (an oily carbohydrate) | Pectin, many with Silicon Dioxide |
| Dinoflagellata (Dinoflagellates) |
Unicellular | Chlorophylls a and c, Carotenoids | Starch | Cellulose |
| Chrysophyta (Golden Algae) |
Mostly Unicellular, Some Colonial | Chlorophylls a and c, Xanthophyll, Carotenoids | Laminarin (an oily carbohydrate) | Cellulose |
| Euglenophyta (Euglenoids) |
Unicellular | Chlorophylls a and b,Carotenoids, Xanthophyll | Paramylon (a Starch) | No Cell Wall, Protein-rich Pellicle |
2. All known Phyla contain the light absorbing Photosynthetic Pigment Chlorophyll a.
3. Different types of Algae also contain other Forms of Chlorophylls-such as Chlorophylls b, c, or d-that absorbs different Wavelengths of light.
4. Some Phyla also have Accessory Pigments that give them their Characteristic Color.
5. Algae live wherever there is Sufficient WATER.
6. They grow in ponds, in salt water, in moist soil, and even on the surface of ice.
7. In Aquatic habitats, Algae have the same basic role as plants on land - that of PRODUCERS.
REPRODUCTION
1. Many Species of Algae Reproduce BOTH Asexually and Sexually. Some species Reproduce only Asexually.
2. Sexual Reproduction is Often Triggered by Environmental Stress.
3. Both Asexual and Sexual Reproduction have been studied in the Unicellular Green Algae Chamydomonas. (Figure 27-1 (a))
A. ASEXUAL REPRODUCTION - It exist as a Flagellated Haploid Cell, during Asexual Reproduction, it First absorbs its Flagellum, then the Haploid Cell divides Mitotically (Mitosis) up to Three Times, and forms from Two to Eight Haploid Flagellated Cells called ZOOSPORES, that develop within the parent cell. These motile Cells break out of the parent cell, disperse, and eventually grow to full size. (Figure 27-2)
B. SEXUAL REPRODUCTION - Begins with Haploid Cells dividing Mitotically (Mitosis) to produce either "Plus" or "Minus" Gametes. A "Plus" Gamete and a "Minus" Gamete come in contact with one another and Shed their Cell Walls. They Fuse and form a Diploid Zygote, which develops a Thick Protective Wall. A Zygote in such a Resting Stage is called a ZYGOSPORE. A Zygospore can withstand unfavorable conditions. When favorable conditions exist, the Thick Wall Opens and the Zoospore emerges. It then undergoes Meiosis, forming Numerous Haploid Cells that grow into mature organisms. (Figure 27-2)
REPRODUCTION IN MULTICELLULAR ALGAE
1. Oedogonium is a Filamentous Green Algae. The Oedogonium has cells specialized for Producing Gametes. (Figure 27-3)
2. The Modified Cells that produce and hold Gametes are called UNICELLULAR GAMETANGIA.
3. The Male Unicellular Gametangia is called an ANTHERIDIUM and produces SPERM.
4. The Female Unicellular Gametangia is called an OOGONIUM and produces an EGG.
5. The Antheridium Releases Flagellated sperm into the surrounding Water, where they swim to an Oogonium and enter through small pores.
6. After Fertilization, the resulting Zygote is released from the Oogonium and forms a Thick Walled, Diploid, Resting Spore. They will undergo Meiosis, forming Four Haploid Zoospores. One of the New Cells becomes a Root-like HOLDFAST, and the others divide and form a New Filament.
7. The Filamentous Green Algae Spirogyra reproduces Sexually by a process called CONJUGATION.
8. During Conjugation, Two Filaments Align Side by side. The walls of adjacent cells dissolve and a Conjugation Tube Forms between the Cells. One cell contains a Plus Gamete, that move through the Conjugation tube, entering the other cell, and fuses with a minus Gamete. After Fertilization, the Zygote forms a Thick Wall, Falls from the Parent and becomes a Resting spore. It latter produces a New Spirogyra Filament.
9. The Leaf-like Alga Ulva
has a Sexual Reproduction Characterized by a pattern called ALTERNATION OF
GENERATIONS. (Figure 27-4)
10. A Life Cycle that Exhibits Alternation of Generations has TWO Distinct Multicellular Phases -
A. A Haploid Gamete Producing Phase called a GAMETOPHYTE PHASE.
B. A Diploid Spore Producing Phase called a SPOROPHYTE PHASE.
11. The Adult Sporophyte has Reproductive Cells called SPORANGIA which produce Haploid Zoospores by Meiosis. The Zoospores Divide Mitotcally and form motile spores, which settle on rocks and grow into Multicellular, Haploid Gametophytes. The Gametophyte looks exactly like the Sporophyte. (Figure 27-4)
12. The Gametophyte produces Gametangia and then produces Plus and Minus Gametes that unite and form Zygotes. The Diploid Zygotes complete the Cycle by dividing Mitotically into New Diploid Sporophytes.
13. Alternation of Generation in Green Algae is important because it also occurs in more complex Land Plants.
14. In plants the Gametophyte and Sporophyte DO NOT Resemble Each other.
15. Also, the Male and Female Gametes (Sperm and egg) in Plants are
developed in Multicellular Reproductive Structures.
SECTION 27-2, ALGAL DIVERSITY
The Seven Phyla of Algae are a showcase of diversity. Microscopic forms, such as diatoms, dinoflagellates, and euglenoids, differ enough to be placed in separate phyla. Pigmentation distinguishes the green algae, red algae, brown algae, and golden algae, which are also placed in separate phyla.
OBJECTIVES: Explain why the phylum Chlorophyta (GREEN) is considered the most diverse phylum of algae. Describe the characteristics of the members of the phyla Phaeophyta (BROWN) and Rhodophyta (RED). Describe the essential characteristics of diatoms, and explain their industrial importance. List the important structural characteristics associated with dinoflagellates. Discuss why Euglena is considered both a protozoan and an algae.
PHYLUM CHLOROPHYTA- GREEN ALGAE
1. The
Phylum Chlorophyta contains more than 7,000 species of organisms called Green
Algae.
2. Their body structures range from Single Cells and Colonial Forms to Multicellular Filaments and Sheets.
3. Most Species are Aquatic, but some also inhabit Moist Land Environments, such as the Soil, Rock Surfaces, and Tree Trunks.
4. GREEN ALGAE (CHLOROPHYTA) are Green and usually Multicellular. Most green algae live in fresh water or in moist soil. Some kinds live on the shallow ocean floor. A few live in Symbiotic Relationships with other organisms or as part of organisms called LICHENS.
5. Biologist believe that Green Algae gave Rise to Land Plants. Evidence supporting this, both groups have Chloroplasts a and b, Both also have Carotenoids and Store Food as Starch. Both also have Cell Walls made of Cellulose.
PHYLUM PHAEOPHYTA - BROWN ALGAE
1.
The Phylum Phaeophyta contains 1,500 species of organisms called Brown Algae.
2. BROWN ALGAE (PHAEOPHYTA) have a Brown Color, are Multicellular, and most grow in Cool Saltwater Habitats. They include the Giant KELPS and SEAWEEDS, the largest organisms (147 - 328 ft long) in the Kingdom Protista. They have specialized structures: rootlike structures called HOLDFAST that anchor the Thallus to rocks, and specialized AIR BLADDERS that causes the Leaflike portion of the Thallus to FLOAT near the Surface. Where it can absorb the sunlight needed for PHOTOSYNTHESIS.
3. The Stem-like portion of the Alga is called the STIPE, and the Leaf-like region, modified to capture sunlight for Photosynthesis, is called the BLADE.
4. The Brown algae contain Chlorophylls a and c and a large amount of the Brown Pigment called FUCOXANTHIN (FYOO-koh-ZAN-thin), which gives them their Brown Color. The food they produce is stored as LAMINARIN, a Carbohydrate with glucose units that are linked together differently than those in starch.
5. Some of the largest algae known are classified in this phylum – Macrocystis (Giant Kelp) can grow to a length of 100 m. The thallus is anchored to the ocean bottom by a rootlike holdfast. The stemlike portion is called the stipe. The leaflike region, modified to capture sunlight for photosynthesis, is called the BLADE.
6. The cell walls of Macrocystis (Giant Kelp) contains Alginic Acid source of ALGINATE and is used in Cosmetics and Various Drugs, as Food, and as a Stabilizer in most Ice Cream.
PHYLUM RHODOPHYTA - RED ALGAE
1.
The Phylum Rhodophyta contains 4,000 species of organisms called Red Algae.
2. RED ALGAE (RHODOPHYTA) are Multicellular organisms and grow in warm Saltwater Habitats. Red Algae have Thalli with Branched Filaments. Besides Chlorophyll a, Red Algae have other PIGMENTS called PHYCOBILINS, that TRAP SUNLIGHT. They allows Red Algae to live in DEEP WATER where there is too little light for most other plants and algae.
3. Despite their common, name, Not all Red Algae are Red. The depth at which they live in the ocean determines the amount of pigment they have.
4. Certain species of Red Algae have Cell Walls coated with a Sticky substance called CARAGEENAN, a polysaccharide used in the production of Cosmetics, Gelatin Capsules, and some types of Cheese. AGAR, which is used as a gel-forming base for culturing microbes is extracted from the cell walls of Red Algae.
PHYLUM BACILLARRIOPHYTA - DIATOMS
1.
The Phylum Bacillariophyta contains 11,500 species of organisms called DIATOMS.
2. DIATOMS ARE ALGAE THAT LACK BOTH CILIA AND FLAGELLA AND HAVE GLASS-LIKE CELL WALLS CONTAINING SILICA (Silicon Dioxide) and are commonly called Shells. (Figure 27-8)
3. Their shells consist of Two pieces that fit together like in a box with a lid. Each half is called a VALVE.
4. There are Two types of Diatoms; CENTRIC DIATOMS have Circular or Triangular Shells and are most abundant in Marine Environments. PENNATE DIATOMS have Rectangular Shells and are most abundant in Fresh Water Pond and Lakes.
5. Some Pennate Diatoms move by secreting threads that attach to the surface of the water. When these threads contract, they pull the diatom forward.
6. Diatoms are an abundant component of Phytoplankton and are important Produces in freshwater and marine food webs.
7. When they die, their shells sink to the bottom of the sea and accumulate forming a layer called DIATOMACCEOUS EARTH.
8. DIATOMACEOUS EARTH is slightly Abrasive and is a major component of many commercial products, such as detergents, paint removers, fertilizers, insulators, and some types of toothpaste.
PHYLUM DINOFLAGELLATES - DINOFLAGELLATES
1.
The Phylum Dinoflagellates contains 1,100 species of organisms called
Dinoflagellates.
2. Dinoflagellates are small, usually Unicellular organisms. Most are Photosynthetic. But a few species are Heterotrophic.
3. Along with diatoms, dinoflagellates are one of the Major Producers of Organic Matter in Marine Environments.
4. DINOFLAGELLATES ARE ALGAE WITH TWO FLAGELLA OF UNEQUAL LENGTH THAT SPIN THE CELLS LIKE A TOP THROUGH THE WATER. (Figure 27-9)
5. The alga is covered by a Cellulose Plate that looks like Armor when seen under a microscope.
6. They can be free-living, or have Symbiotic relationships with other organisms. Symbiotic Dinoflagellates DO NOT have Flagella.
7. Some species (Noctiluca) can produce BIOLUMINESCECE, a display of sparkling light often seen in the Ocean at night.
8. Other species produce Toxins and Red Pigments. When their populations Explode, they turn the water brownish red, resulting in a phenomenon known as RED TIDE. (Noctiluca)
9. When Shellfish including oysters, feed on the Dinoflagellates, they also consume the Toxins, which are dangerous to humans who eat the Shellfish.
PHYLUM CHRYSOPHYTA - GOLDEN ALGAE
1. The Phylum Chrysophyta contain 850 species of organisms called Golden Algae.
2. Most live in Fresh Water, but a few are found in Marine Environments.
3. The Cells form Highly Resistant Cysts that enable them to survive beneath frozen surfaces of lakes in winter and dry lake beds during summer.
4. Two Flagella of unequal length are located at one end of each cell.
5. Most species are some shade of Yellow or Brown due to the presence of large amounts of Carotenoids.
6. Golden Algae store much of their surplus energy as OIL and are important in the formation of Petroleum Deposits.
PHYLUM EUGLENOPHYTA - EUGLENOIDS
1. The Phylum Euglenophyta contains
1,000 species of Flagellated organisms called Euglenoids.
2. EUGLENOIDS ARE ORGANISMS THAT HAVE NO RIGID CELL WALL, HAS A FLEXIBLE PROTEIN COVERING CALLED PELLICLE, AND THEY HAVE TWO FLAGELLA.
3. They show characteristics of both Algae (plant-like), many have Chlorophyll and are Photosynthetic, and Protozoans (animal-like) they Lack a Cell Wall and are Highly Motile.
4. Most species live in Fresh Water, but a few are found in Moist Environments, in the Soil or in the Digestive Tract of Certain Animals.
5. A Familiar genus of Euglenoids is Euglena, this protists is abundant in freshwater, has an elastic transparent pellicle beneath its cell membrane, it also has a Contractile Vacuole to rid the cell of excess water. (Figure 27-10)
6. The Euglena is usually Photosynthetic, but if raised in a Dark environment, it will not form Chloroplasts and will be Heterotrophic.
SECTION 27-3 FUNGUSLIKE PROTIST
The Kingdom Protista contains a number of fungilike protists in addition to the algae. Among these are the slime molds and water molds. These organisms have unique life cycles that set them apart from the protozoa, algae and fungi. They are Eukaryotic, Multicellular or large Multinucleate Heterotrophic organisms with very little tissue specialization.
OBJECTIVES: Describe the two forms that characterize the life cycle of the slime mold. Describe the environment in which slime molds live. Outline the basic life cycles of the two groups of slime molds. Point out the unique characteristics of water molds.
1. Most Funguslike Protists are small and live in damp or watery places, helping to break down dead organic matter.
2. Funguslike Protists are divided into THREE Groups:
A. CELLULAR SLIME MOLDS
B. PLASMODIAL SLIME MOLDS
C. WATER MOLDS
SLIME MOLDS
1.
Funguslike Protists are called Slime Molds because they have a Shiny, Wet
Appearance, a Texture like Gelatin, and look more like a Mold or Fungus than
anything else. Some are White, but most are Yellow or Red.
2. They spend part of their lives in a Mobile, amoeba-like Feeding form, engulfing organic matter and bacteria much as protozoa do. They also produce Fungus-like Reproductive Structures.
3. Most Slime Molds and Water Molds are DECOMPOSERS; THEY GET THEIR NUTRIENTS FROM DEAD ORGANISMS OR THE REMAINS OF DEAD ORGANISMS.
4. Slime molds are typically found growing on Damp soil, Rotting logs, decaying Leaves, or other decomposing organic matter in moist places.
5. Biologist recognized Two groups of Slime Molds- the Cellular Slime Molds (Phylum Acrasiomycota) and the Plasmodial Slime Molds (Phylum Myxomycota).
6. Both types have life cycles with Two Phases: a Mobile Feeding Stage and a Stationary Reproductive Stage.
7. During Reproduction, Slime Molds produce a Spore-bearing Structure called a FRUITING BODY.
PHYLUM ACRASIOMYCOTA - CELLULAR SLIME MOLDS
1. CELLULAR SLIME MOLDS alternate
between an amoeboid form and a defined spore-producing Fruiting Body. (Figure
27-11)
2. Most live in Fresh Water, Damp Soil, or on decomposing plant matter. When there is little food available they will clump together and resemble a plasmodial slime mold.
3. THE CLUMP IS KNOWN AS A PSEUDOPLASMODIUM (A False Plasmodium) BECAUSE IT CONSISTS OF INDEPENDENT CELLS THAT RESEMBLES A SLUG.
4. The Cells within the clump move as one unit, but each cell maintains its independent identity within its own cell membrane.
5. Eventually the Pseudoplasmodium settles and Forms a Fruiting Body in which Haploid Spores Develop. When the fruiting body breaks open, the Wind Disperses the spores to new locations. Each spore may grow into an individual Amoeboid Cell, thus completing the life cycle.
PHYLUM MYXOMYCOTA - PLASMODIAL SLIME MOLD
1. PLASMODIAL SLIME MOLDS come in many different colors, and have different forms at different stages in their Life Cycle.
2. When they are Feeding, plasmodial slime molds form a mass of Cytoplasm called a PLASMODIUM. Each Plasmodium is Multinucleated, containing thousands of Nuclei.
3. A PLASMODIUM IS THE FEEDING STAGE IN THE LIFE CYCLE OF A PLASMODIAL SLIME MOLD.
4. The Plasmodium creeps around the ground, rocks and decaying logs eating Bacteria and other small organisms as it moves by Phagocytosis.
5. When food or water is Scarce, the plasmodium crawls to an exposed surface and begins to reproduce. (Figure 27-12)
6. It forms Stalked Fruiting Bodies, which Haploid Spores Form by Meiosis. The spores are very resistant to adverse conditions.
7. Under Favorable Conditions, the spores crack open and give rise to Haploid Reproductive Cells. Two cells fuse together and their Nuclei Combined to form a Diploid Nucleus. Repeated divisions by Mitosis follow, but the cells do NOT undergo Cytokinesis, so the result is the Multinucleated Cytoplasm characteristic of the Plasmodium.
WATER MOLDS
1. A WATER MOLD is a funguslike organism composing of branching filaments of cells
2. WATER MOLDS, these are decomposers or parasites that typically grow in fresh water on decaying plants and animals. Rusts and Mildews are also considered Water Molds.
3. Water Molds are familiar as the white fuzz on diseased aquarium fish or on organic matter floating on water.
PHYLUM OOMYCOTA
1. The Phylum Oomycota includes a number of organism that are pathogenic to plants.
2. One infamous water mold Phytophthora infestans, is known for damaging Irish potato crops (BLIGHT) in the nineteenth century and started a famine that killed nearly 2 million people.
3. Blight is a Disease of plants characterized by quickly developing Decay and discoloring of Leaves, Stems, and Flowers. (Figure 27-13)
4. Plasmopara viticola infects Grape Plants, attacking the Leaves and the Fruit. Plasmopara infection causes the grape leaves to wilt and die. Plasmopara may also infect vegetables and other fruits. (Figure 27-14)
5. Water Molds Reproduce Asexually and Sexually.
6. During Asexual Reproduction, they produce motile, Flagellated Reproductive Zoospores. Zoospores Germinate into threadlike cells, some Zoospores from Reproductive Structures called Sporangium, in which new Zoospores are produced.
7. During Sexual Reproduction, the cells of the Water Mold develop Egg-Containing and Sperm-Containing Structures. Fertilization Tubes grow between the Two types of structures, enabling the Haploid Sperm Cells to Fertilize the Haploid Egg Cells and form Diploid Zygotes. A Zygote develops into a new mass of filaments, from which Asexual Sporangia as well as Sexual Oogonia and Antheridia form.
PHYLUM CHYTRIDIOMYCOTA - CHYTRIDS
1. The CHYTRIDS (KIE-tridz) are primarily Aquatic protists characterized by gametes and zoospores with a Single, Posterior Flagellum. (Figure 27-15)
2. Most are Unicellular, Some have long filamentous bodies that anchor the organism, Many are Parasites on algae, Plants, and Insects, while others are Saprophytes.
3. Many Biologists not think Chytrids should be classified as Fungi. They Both have similar characteristics; they have similar methods of absorbing nutrients through the cell wall, cell walls that are made of the same type of material, and long filamentous bodies.
4. Because of all these similarities, Biologists think that Chytrids are a link between Protists and Fungi.