chapter 19. protists are of enormous eco-logical importance photoautotrophic forms: produce...
TRANSCRIPT
Chapter 19
Protists are of enormous eco-logical importance
Photoautotrophic forms: Produce oxygen Function as producers in both freshwater and
saltwater ecosystems Major component of plankton
Organisms that are suspended in the water Serve as food for heterotrophic protists and
animals
Many protists are symbionts
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Objectives Identify the characteristics of the
Kingdom Protista Compare and contrast the four
groups of protozoan
Colorless heterotrophs Most symbiotic and many parasitic Well known for causing various diseases in
humans Trypanosoma
African sleeping sickness - Tsetse fly Chagas disease – Kissing bug
Giardia lamblia Most common flagellate in human digestive tract Causes severe diarrhea Cysts are transmitted in contaminated water Beavers are important reservoir hosts
Trichomonas vaginalis Sexually transmitted protist, Infects urogenital organs; a common cause of
vaginitis5
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Pseudopods form when cytoplasm streams forward in a particular direction
Amoeboids (phylum Rhizopoda) are protists that move and ingest their food with pseudopods Phagocytize food Entamoeba histolytica - a parasite of the human
colon; Causes amoebic dysentery Can be fatal
Foraminiferans (phylum Foraminifera) and radiolarians (phlyum Actinopoda) Both have a skeleton (test) of either calcite or
silica8
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Ciliates (phylum Ciliophora) are among the most complex of the protozoans Hundreds of cilia beat in coordinated
rhythm Most are holozoic, swallowing food
whole usually asexual
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Nonmotile obligate parasites Most serious parasitic disease of
human is malaria Plasmodium spp
Kills 3,000,000 people each year Transmitted by mosquito
Toxoplasma Humans get from cats Causes birth defects and mental retardation
when pregnant mom exposed
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Objectives Compare and contrast the variety of
plant-like protists Explain the process of alteration of
generations in algae
Phylum Chlorophyta Approximately 7,500 species Inhabit oceans, freshwater, snowbanks, tree
bark, and turtles backs Many are symbionts with fungi, plants, or
animals unicellular, multicellular Morphology
cell wall that contains cellulose Possess chlorophylls a and b, and Store excess food as starch
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A minute (<25 μ m), actively moving flagellate
Inhabits still, freshwater pools
Fossil ancestors date back over a billion years
Anatomy: Definite cell wall Single, large, cup-shaped chloroplast Many with a bright red eyespot, or stigma on
chloroplast Two long, whip-like flagella
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Multicellular About 5,000 species Live mostly in warmer seawater, some as
deep as 200 m Economic Importance
Agar - capsules; dental impressions; cosmetics; culture medium; electrophoresis; food prep.
Carrageen - an emulsifying agent used in chocolate, low-fat foods, & cosmetics
The reddish-black wrappings around sushi rolls consist of processed Porphyra blades
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About 1,500 species Most live in colder ocean waters along rocky
coasts No unicellular or colonial brown forms Morphology:
simple filaments large multicellular forms that may exceed 200 m in
length Pigments:
Chlorophylls a and c carotinoid pigment gives them their color
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Multicellular forms of green, red, and brown algae are called seaweeds Laminaria (a kelp), and Fucus, (rockweed), are
common intertidal seaweeds Nereocystis and Macrocystis often form forest-
like thickets in deeper waters Sargassum forms floating masses where other
organisms find shelter
Harvested for food and fertilizer Macrocystis is source of algin, a thickener
for foods
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Diatoms (formerly Bacillariophyta) are the most numerous unicellular algae in the oceans
Significant portion of phytoplankton Cell wall Contains silica Diatomaceous earth used as
Filtering agents Sound-proofing materials Polishing abrasives
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About 4,000 species of unicellular aquatic and marine organisms
Morphology: Cell walls Typically with two flagella Symbiotic with corals Some lack chloroplasts and are parasitic
Gymnodinium brevis may cause “red tide” Produce a powerful neurotoxin that has caused
massive fish kills Consume shellfish during outbreak can cause
respiratory paralysis
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Small freshwater unicellular organisms Lack cell wall Have two flagella and an eyespot Have Chloroplasts so are photosynthetic
If light is not available can ingest food
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Algae go through an alternation of generations Alternate between haploid
(gametophyte)and diploid (sporophyte) body forms
Objectives Contrast the cellular differences and
life cycles of the two types of slime molds
Discuss the economic importance of downy mildews and water molds
Plasmodial Slime Molds - Phylum Myxomycota Body in the form of a plasmodium
Diploid, multinucleated, cytoplasmic mass Enveloped by a slimy sheath
Eventually produces sporangium which in turn produces spores
Cellular Slime Mold - Phylum Acrasiomycota Body in the form of individual amoeboid cells Later aggregate into pseudoplasmodium which
then forms sporangium & spores
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Most live in the water Body filamentous, appearing like true
Fungi Cell walls largely of cellulose rather than
chitin The organism is diploid
Phytophthora infestans caused the 1840’s potato famine in Ireland
Saprolegnia is often seen as a white, cotton-like coating on dead aquarium fish
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Origin of Protists Some protists share characteristics of
plants, animals, and fungus Shared common ancestor
Ancient green algae ancestor to plants