Mader: Biology 8th Ed.

The Protists

Chapter 22

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Mader: Biology 8th Ed.

Outline

• General Biology

• Evolution

• Diversity

– Green Algae

– Red Algae

– Brown Algae

– Diatoms

– Dinoflagellates

• Diversity

– Euglenoids

– Zooflagellates

– Pseudopods

– Ciliates

– Sporozoans

– Slime Molds

– Water Molds

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General Biology of the Protists

• Protists are classified in the domain Eukarya and the kingdom Protista.

– Most are unicellular, but have achieved a high level of complexity.

– Asexual reproduction is common, but sexual reproduction can occur when the environment becomes stressful.

!Spores

!Cysts

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Origin of Eukaryotic Cell

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Evolution of Protists

• Complexity and diversity of protists makes them difficult to classify.

– Cannot be classified as plants, animals, or fungi.

– Has been suggested protists could be split into as many as a dozen kingdoms.

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Diversity of Protists

• Green Algae

– Green algae (phylum Chlorophyta).

!Chlamydomonas

"Unicellular

"Usually reproduces asexually

# Forms spores and zoospores when growth conditions are unfavorable.

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Green Algae

– Spirogyra

!Unbranched, filamentous alga found in masses on the surfaces of standing water.

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Green Algae

– Multicellular

!Ulva

!Stoneworts

!Chara

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Green Algae

– Colonial

!Volvox

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Flagellated Protists

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Red Algae

• Red Algae (phylum Rhodophyta)

– Multicellular, and live mostly in warmer seawater.

!Usually much smaller and more delicate than brown algae.

!Economic Importance

"Agar

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Brown Algae

• Brown Algae (phylum Phaeophyta)

– Have chlorophylls a and c in their chloroplasts and a carotenoid pigment.

– Often observed on rocky coasts in north temperate zone.

!Seaweeds

!Kelp

!Fucus

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Brown Algae

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The Diatoms

• Diatoms (phylum Bacillariophyta) are the most numerous unicellular algae in the oceans.

– Significant portion of phytoplankton.

– Structure composed of two valves, with the larger valve acting as a lid.

– Cell wall has outer layer of silica.

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The Dinoflagellates

• Most dinoflagellates (phylum Pyrrophyta) are unicellular.

– Usually bounded by protective cellulose plates impregnated with silicates.

!Typically contain two flagella.

!Chloroplasts vary in color.

!Usually reproduce asexually.

!Some genera may cause red tide.

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Diatoms and Dinoflagellates

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The Euglenoids

• Euglenoids (phylum Euglenophyta) are small freshwater unicellular organisms.

– Difficult to classify.

– Have two flagella and an eyespot (shades a photoreceptor).

– Bound by flexible pellicle.

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Euglena

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The Zooflagellates

• Zooflagellates (phylum Zoomastigophora) are colorless heterotrophs.

– Most are symbiotic and many are parasitic.

– Well known for causing various diseases in humans.

!African sleeping sickness

!Giardia lamblia

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Zooflagellates

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Protists with Pseudopods

• 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.

– Foraminiferans (phylum Foraminifera) and radiolarians (phlyum Actinopoda) both have a skeleton (test).

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Protists with Pseudopods

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Amoeboid Protists

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The Ciliates

• Ciliates (phylum Ciliophora) are most complex of the protozoans.

– Hundreds of cilia beat in coordinated rhythm.

– Most are holozoic.

– Divide by transverse binary fission during asexual reproduction.

– High level of diversity.

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Ciliates

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Ciliated Protists

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The Sporozoans

• Sporozoans (phylum Apicomplexa) are nonmotile parasites.

– Most widespread human parasite is Plasmodium vivax, the cause of one form of malaria.

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Plasmodium vivax Life Cycle

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Slime Molds

• Plasmodial Slime Molds

– (phylum Myxomycota) usually exist as a plasmodium.

!Diploid, multinucleated, cytoplasmic mass enveloped by a slime sheath.

"Sporangium produces spores.

• Cellular Slime Mold

– (phylum Acrasiomycota) exists as individual amoeboid cells.

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Plasmodial Slime Molds

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Water Molds

• Water molds (phylum Oomycota) usually live in the water and form furry growths when they parasitize fish and decompose remains.

– Have filamentous body with cell walls largely composed of cellulose.

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Review

• General Biology

• Evolution

• Diversity

– Green Algae

– Red Algae

– Brown Algae

– Diatoms

– Dinoflagellates

• Diversity

– Euglenoids

– Zooflagellates

– Pseudopods

– Ciliates

– Sporozoans

– Slime Molds

– Water Molds

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