Features of Kingdom Protista Members are eukaryotic cells: unicellular, multicellular, or occur as colonies or filaments. Individual life cycles vary considerably, but reproduction is generally by cell division and sexual processes. Most multicellular members produce some motile cells. Mode of nutrition is photosynthetic, ingestive, or combination of both.
Phylum Chlorophyta The Green Algae Includes about 7,500 species that occur in a rich variety of forms and occur in diverse, widespread habitats. - Greatest variety found in freshwater lakes, ponds, and streams. - Most have a single nucleus. - Most reproduce both sexually and asexually.
Phylum Chlorophyta Chlamydomonas Common inhabitant of freshwater pools. Pair of whip-like flagella on one end pull the cell through the water. Red eye spot on the chloroplast and is sensitive to light. Single, cup-shaped chloroplast with one or two pyrenoids inside. - Proteinaceous structures thought to contain starch synthesis enzymes.
Asexual Reproduction - Cells are haploid (n) Nucleus divides by mitosis, and cell contents become two daughter cells within the cellulose wall. - Develop flagella and swim away.
Sexual Reproduction - Under certain environmental conditions, pairs of cells (n) are attracted to each other and function as gametes. - Protoplasts fuse to form a diploid zygote (2n). - Diploid zygotes undergo meiosis (genetic recombination), producing four haploid (n) zoopsores.
Sexual Life Cycle of Chlamydomonas
Phylum Chlorophyta Ulothrix Thread-like alga. - Single row of cylindrical cells forming a filament. Basal cell functions as a holdfast. - Nucleus is surrounded by a curved, somewhat flattened chloroplast, which contains one or more pyrenoids.
Asexual Reproduction - Protoplasts of any cell but the holdfast can clump, undergo mitosis, and give rise to zoopsopres with four flagella. - Zoopsores swim away then settle, lose their flagella and start dividing producing two cells. One cell becomes holdfast and the other continues to divide to for a filament. - Zoopsores sometimes dont produce flagella (autospores) while the zoospores that have the capacity to become motile are called aplanospores.
Sexual Reproduction (isogamy) Asexual and sexual reproduction satrt the same way. The contents of any cells may divide by mitosis to produce up to 64 Zoosporelike cells, each with 2 flagella. These cells act as gametes and fuse in pairs with cells from other filament to produce zygotes (2n). Zygotes are dormant with thick walls but conditions are favorable they divide by meiosis to produce 4 haploid zoospores that can divide by mitosis to produce a new filament.
Ulothrix Life Cycle
Phylum Chlorophyta Spirogyra (Watersilk) Common freshwater algae consisting of unbranched filaments of cylindrical cells. - Frequently float in masses at the surface of quiet waters. - Chloroplasts are long and ribbon-shaped. Asexual Reproduction - No not form zoospores. Any cell capable of division. - Fragmentation of existing filaments. Sexual Reproduction (oogamy) - Papillae from adjacent filaments fuse to form conjugation tubes. - Condensed protoplasts function as gametes. - Zygotes develop thick walls and remain dormant, often over winter. - Protoplasts undergo meiosis, producing four haploid cells.
Spirogyra Sexual Reproduction
Phylum Chlorophyta Oedogonium (pronounced ee-doh-goh-nee-um) Epiphytic (not parasitic) filamentous green alga. - Each cell contains a large, netlike chloroplast that rolls and forms a tube around and toward the periphery of each protoplast. - Terminal cell of each filament is rounded.
Asexual Reproduction: - By means of zoospores or fragmentation. - Each zoopsore has about 120 small flagella forming a fringe. Sexual Reproduction: - Short antheridia are formed in the filaments. - Pair of sperms produced in each antheridium. - Oogonia, swollen roundish cells, each contain a single egg. In some species of Oedogonium, oogonia are produced only on female filaments, and antheridia are produced only on only on male filaments. - As egg matures, a pore develops on the side of the oogonium. - A sperm enters the pore and unites with the egg to form a zygote. - Zygotes may become dormant, but each will produce four zoospores by meiosis.
Phylum Chlorophyta Other Green Algae Chorella - Widespread green alga composed of tiny spherical cells. - Reproduce by forming either daughter cells or autospores through mitosis. Desmids - Mostly free-floating and unicellular. - Reproduce by conjugation.
Phylum Chlorophyta Other Green Algae Hydrodictyon (Water Nets) - Net-like, tubular colonies with hexagonal or polygonal meshes. - Asexual reproduction as well as isogamous sexual reproduction. Volvox - Colonial green algae held together in a secretion of gelatinous material - Reproduction asexual or sexual.
Phylum Chlorophyta Other Green Algae Ulva (Sea Lettuce) - Multicellular seaweed with flattened green blades. - Isomorphic reproductive structures. Cladophora - Branched, filamentous green alga with species represented in both fresh and marine waters. - Mostly multinucleate.
Phylum Chromophyta The Brown Algae (Phaeophyceae) Includes 1,500-2,000 species Relatively Large Most Marine None are unicellular or colonial Many have a thallus differentiated into a holdfast, a stipe, and blades. - Blades may have gas-filled bladders. - Chloroplasts have chlorophylls a and c and the brownish pigment fucoxanthin - Carbohydrate food reserve is laminarin - Cell walls contain algin (alginic acid) Sargassum - Floating brown seaweed plentiful in tropical waters near Bermuda.
Brown Alga Nereocystis
Fucus - Common Rockweed Has separate male and female thalli. Puffy fertile areas (receptacles) develop at the tips of the thalli. Receptacles have pores leading to hollow chambers called conceptacles. Gametangia are formed in conceptacles: - Eight eggs produced in each oogonium. - 64 sperms produced in each antheridium.
Phylum Rhodophyta The Red Algae More than 5,000 species and most species are seaweed. - Tend to occur in warmer and deeper waters than brown algae. Most are filamentous. Relatively complex life cycle involving three types of thallus structures. Colors mostly due to phycobilins. Numbers of species produce agar. Red to purple in color due to phycobilins. Chloroplasts contain chlorophylls a and d. Carbohydrate food reserve is floridean starch.
Reproduction in Polysiphonia Three types of thalli all resemble each other Spermatangia attached to male gametophyte thallus and functions as non-motile male gamete or spermatium. Carpogonia produced on female gametophyte thallus. Each carpogonium consists of a single bottle-shaped cell with long neck called the trichogyne. A single nucleus at the base of the carposgonium functions as the egg. Zygote develops into cluster of carposporangia toward the base of the carpocyst. - Carpospores (diploid asexual spores) are produced). - When settled in an appropriate location, carpospore germinates and develops into a tetrasporophyte. - Tetrasporangia form along branches of the tetratsporophyte. - Each tetrasporangium undergoes meiosis, giving rise to four haploid tetraspores. - When tetraspores germinate, they give rise to male or female gametophyte.
Human and Ecological Relevance of Algae A. Chlorella, important protein source B. 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
Human and Ecological Relevance Algae C. 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. Carrage