chapter 19. protists are of enormous eco-logical importance photoautotrophic forms: produce...

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

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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