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MAIN TOPICS OUTLINE
20.1 GENERAL CHARACTERISTICS
20.11 Cell organization
20.12 Reproduction and Life cycles
20.13 Habitat
20.2 CLASSIFICATION
20.21 Plant-like protistans (Algae)
20.22 Mold-like protistans
20.23 Animal-like protistans
LECTURE OBJECTIVES
1. Discuss the characteristics of the kingdom Protista, and some criteria used in classifying protistans.
2. List the three major groups of protistans and their differences
3. List the major phyla of the protistans, give some examples of each, and list some beneficial and harmful protistans, including some parasites.
4. List the way protistans differ from bacteria.
5. Define selected key terms.
Key Terms:def. alternation of generations: A sexual life cycle in which haploid (gametophyte) and diploid (sporophyte) phases alternate.
def. autotrophs: organisms capable of producing their own food from inorganic materials & sunlight (or another environmental energy source).
def. binary fission: Asexual reproduction in bacteria and protista (in which a cell pinches in two, distributing its material to the two daughter cells).
def. cilia (sing. cilium): Short hair-like structures of many cells (not necessarily free-living). [Compare w. "flagella".]
def. conjugation: "Sexual reproduction" in bacteria and protista, a mechanism by which a donor cell transfers genetic material to a recipient cell (usually another bacteria).
def. diploid: The condition of having two sets of chromosomes per nucleus (one from each of two parents).
def. endosymbiotic theory (hypothesis): The idea that eukaryotic cells evolved from large prokaryotic cells that engulfed once free-living bacteria -- now mitochondria and chloroplasts.
def. flagella (sing. flagellum): Tail-like structures of many free-living cells. [Compare w. "cilia".]
def. gametophyte: haploid form of a life cycle of a plant, characterized by "alternation of generations", (produce gametes).
def. haploid: The condition of having one set of chromosomes per nucleus.
def. heterotrophs: organisms incapable of producing their own food, and therefore depend directly or indirectly on producers to meet their food requirements.
def. isogamy: A condition when male and female gametes are morphologically similar.
def. motile: Moving or having the power to move. . [Compare w. "sessile".]
def. mutualism: Ecological relationship between two organisms where both organisms benefit.
def. oogamy: A condition when male and female gametes are morphologically different, e.g., a small, motile, flagellated sperm fertilizes a large, nonmotile egg.
def. parasite: Heterotrophic organism that obtains nourishment from another organism called the host.
def. parasitism: Ecological relationship between two organisms where only one organism benefits, by deriving nourishment from the other, without killing it (at least not immediately) but usually doing harm to it.
def. phagocytosis: Cellular ingestion (engulfing) in which the membrane of the cell surrounds a relatively large solid particle, such as a microorganism or cell debris. (Feeding method of many holozoic protozoa.)
def. photosynthesis: the conversion of light energy to chemical energy (stored in glucose produced) from carbon dioxide and water.
def. plankton: Organisms (usually microscopic) floating or weakly swimming in freshwater or saltwater, carried by currents. (There are two forms: zooplankton [animal-like] and phytoplankton [plant-like].)
def. pseudopodium(pl. pseudopodia, also called pseudopod): temporary extension of the cytoplasm, used for locomotion and engulfing food by some protozoa.
def. red tide: A population explosion or bloom of microscopic protista, called dinoflagellates, containing toxins that can poison marine life.
def. sessile: Permanently anchored (e.g., to rocks, logs, or coral), not having the power to move. . [Compare w. "motile".]
def. sporophyta: diploid form of a life cycle of a plant, characterized by "alternation of generations" (produce spore-bearing structures).
20. 1 General Characteristics
• The Protista is a diverse group of unicellular and multicellular eukaryotic organisms that inhabit aquatic or moist habitats.
Over 65,000 species of protistans have been identified, and the relationships between these organisms are constantly being revised and updated. It is difficult to come up with general characteristics for the group.
"Kingdom at the Crossroads" -- "The Lumping Kingdom"
1. eukaryotic
2. aerobic
3. some are unicellular, some are multicellular
4. some have cell wall, some do not have cell wall
5. some are autotrophic, some are heterotrophic
6. some are small, some are large (larger than bacteria)
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• 20. 11 Cell Organization
• Most protista are unicellular. As a group they are considered to be the simplest of the eukaryotic kingdoms (in the Domain Eukarya).
-- However, at the cellular level many protista are extremely elaborate and complex.
(Each unicellular protista is not like a single cell of a human or another multicellular organisms, but is itself a complete organism, as any plant or animal.)
• Endosymbiotic theory (hypothesis): Eukaryotic cells evolved from large prokaryotic cells that engulfed once free-living bacteria -- now mitochondria and chloroplasts.
• 20. 12 Reproduction and Life Cycles
• The Protista have very different reproduction methods and life cycles:
i. Diplontic: life cycle & reproduction like animals
- diploid multicellular stage (only the gametes formed after meiosis are haploid)
- Diploid stage: the zygote + the adult
- Haploid stage: the gametes
ii. Alternation of generations: life cycle & reproduction like plants
- both diploid (sporophyte) and haploid (gametophyte) multicellular stages
- Diploid stage: the zygote + the sporophyte adult
- Haploid stage: the gametes + the gametophyte adult + the spores
iii. Haplontic: life cycle & reproduction like fungi
- haploid multicellular stage (only the zygote, formed after fertilization, is diploid)
- Diploid stage: the zygote
- Haploid stage: the gametes + the adult
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• 20. 13 Habitat
def. motile: Moving or having the power to move. . [Compare w. "sessile".]
def. sessile: Permanently anchored (e.g., to rocks, logs, or coral), not having the power to move. . [Compare w. "motile".]
def. plankton: Organisms (usually microscopic) floating or weakly swimming in freshwater or saltwater, carried by currents. (There are two forms: zooplankton [animal-like] and phytoplankton [plant-like].)
• The Protista are found almost anywhere there is water
i. oceans
ii. ponds
iii. lakes
iv. rivers
v. damp soil
vi. leaf litter
vii. other terrestrial habitats with moisture
• The Protista are important organisms in plankton communities
def. plankton: Organisms (usually microscopic) floating or weakly swimming in freshwater or saltwater, carried by currents. (There are two forms: zooplankton [animal-like] and phytoplankton [plant-like].)
Ecologically important:
i. First link in marine and freshwater food webs.
ii. Major oxygen producers on this planet:
50% phytoplankton in the oceans50% land plants (40% from the tropical rainforests)20.2 Classification
As already stated, the Protista is a diverse group of unicellular and multicellular eukaryotic organisms, and the relationships between these organisms are constantly being revised and updated.
• 20.21 Plant-like protistans (Algae)
• Green color -- Chlorophyll (green pigment) -- Photosynthesizing organisms (autotrophs). Algae is a term used for a large group of photosynthetic protistans, many are planktons (phytoplanktons).
• Can use energy from the sun directly: Autotrophs -- self-feeders
def. Autotrophs: organisms capable of producing their own food from inorganic materials & sunlight (or another environmental energy source).
def. Photosynthesis: the conversion of light energy to chemical energy (stored in glucose produced) from carbon dioxide and water.
sunlight + 6CO2 + 6H2O >>> C6H12O6 + 6O2
i. Phylum Chrysophyta (Diatoms)
• Unicellular, golden, brownish color, plankton
Have chlorophyll, but masked by other pigments (not green). Economic importance: Have a shell which the industry use to make abrasive materials or filter materials.
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ii. Phylum Dinoflagella (Dinoflagellates) also called Pyrrhophyta
• Unicellular, often red color, plankton. Cause Red tides, and Fish Death (ÒThe Cell from HellÓ).
Gonyaulax, Gymnodinium, "Red Tides" When present in large numbers, are capable of producing toxins that harm other organisms, including humans.
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Pfiesteria piscicida, "the Cell from Hell"
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CNN | ../CNN_Starr_Taggart_f/KillerAlgae.mov |
Have chlorophyll, but masked by other pigments (usually not green). Have flagella in grooves.
def. red tide: A population explosion or bloom of microscopic protista, called dinoflagellates, containing toxins that can poison marine life.
iii. Phylum Euglenophyta (Euglenoids)
• Unicellular, green color, motile
Free-living, both heterothoph and autotroph (animal or plant?)
• Euglena
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iv. Phylum Chlorophyta (Green Algae)
• Unicellular or multicellular green color, (unicellular usually motile).
Economic importance: Some sold dry in health food stores. The closest relatives to the plants!
• Volvox, • Spirogyra, • Ulva (sea lettuce)
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v. Phylum Phaeophyta (Brown Algae)
• Multicellular, brown color, sessile
Have chlorophyll, but masked by brown pigments (phycobilins). Economic importance: used as thickening agent in food.
Sea weeds (rock weeds, kelps): • Fucus, • Sargassum, • Laminaria
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vi. Phylum Rhodophyta (Red Algae)
• Multicellular, red color, sessile
Have chlorophyll, but masked by red pigments (xanthophylls) which can trap sunlight in deep marine waters! Economic importance: Some sold dry in health food stores, some used for agar (used in microbiology as growth medium for bacteria, and as ice cream stabilizer)
• Chondrus (Irish moss)
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• 20.22 Mold-like protistans (Water and Slime Molds)
• Natural color NOT green -- no chlorophyll -- do not photosynthesize (heterotrophs)
i. Phylum Oomycota (Water Molds)
• Free-living, or parasite on plants -- Cause Irish Potato Blight. Sessile.
Some parasitic on aquarium fish!
The blight was the fungus Phytophthora infestans which destroyed potato plants and was the principal cause of what came to be known as the Irish Potato Famine. The blight wiped out the potato crop in 1845, 1846 and again in 1848. People were left with nothing to eat and no way to make money to support themselves. Many wandered the countryside, begging for food or work. Others ate grass and weeds to survive. Those who could afford to, left the country in search of a better life. Canada's Digital Collections (http://collections.ic.gc.ca/potato/history/ireland.asp)
ii. Phylum Myxomycota (Slime Molds) also called Gymnomycota
• Free-living. Motile (often as "steaming" gel masses)
Amoeba-like, slimy masses that can migrate to find food!
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• 20.23 Animal-like protistans (Protozoa)
• Natural color NOT green -- no chlorophyll -- do not photosynthesize (heterotrophs)
• Cannot use the sun directly -- must feed on something: Heterotrophs
def. Heterotrophs: organisms incapable of producing their own food, and therefore depend directly or indirectly on producers to meet their food requirements.
def. parasitism: Ecological relationship between two organisms where only one organism benefits, by deriving nourishment from the other, without killing it (at least not immediately) but usually doing harm to it.
def. mutualism: Ecological relationship between two organisms where both organisms benefit.
i. Phylum Sarcodina (Amoebas)
• Amoeba
• Free-living, or parasite. May cause disease. Motile.
Characteristic of this group: pseudopodia -- cytoplasmic extensions of the cell body.
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ii. Phylum Ciliophora (Ciliates)
• Paramecium
• Free-living, ciliated protozoa. In ponds, do not cause disease. Motile.
Characteristic of this group: cilia -- numerous hairlike structures that beat in synchrony on the cell surface.
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iii. Phylum Sporozoa (Sporozoans)
• Plasmodium
• Parasite -- cause Malaria (fever). Motile
Characteristic of this group: all parasitic -- must live inside of cells part of their life. Malaria: serious world wide disease! 150 - 300 million new cases per year. Transmitted by a mosquito (Anopheles)
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iv. Phylum Zoomastigophora (Zooflagellates)
• Parasites. Motile
Characteristic of this group: flagella -- few tail-like structures on the cell surface.
• Trypanosoma
a. Sleeping sickness in Africa
(Trypanosoma gambiense. Cause coma. Transmitted by the tse-tse fly (Glossina) (many areas in Africa uninhabitable.)
b. Chaga's disease in South and Central America
(Trypanosoma cruzi. Cause heart disease, enlarged intestines, CNS.) Transmitted by the Kissing Bug [family Reduviidae]
• Giardia -- hiker’s diarrhea
• Trichomonas -- Trichomoniasis (STD of urinary and reproductive organs).
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Dr. Thinkwell | ../Thinkwell_f/20_Protista1_5495_5518.mov |
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Copyright 2002, 2003, 2004, Jan A. Nilsson. Web page layout and design © and intellectual property Jan A. Nilsson. All rights reserved. Reproduction of the whole or any part of the contents without written permission is prohibited. Page created 10.XII.2002, last updated 16.II.2004, most likely during the wee hours of the morning on a G3 PowerBook owned by Jan A. Nilsson.
-- Disclaimer: "Dr. Nilsson's CyberOffice", at the time of writing located as a file under the South Texas Community College's (STCC) web server with the general URL http://stcc.cc.tx.us/, is the intellectual property of Dr. Jan A. Nilsson, member of STCC biology faculty. The content of Dr. Nilsson's CyberOffice does not necessarily reflect the opinions and beliefs of the STCC faculty, staff, administration, and Board of Trustees.