Mader: Biology 8th Ed.

The Protists

Chapter 22

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

Mader: Biology 8th Ed.

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.

SporesCysts

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Origin of Eukaryotic Cell

Mader: Biology 8th Ed.

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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Mader: Biology 8th Ed.

Green Algae

– SpirogyraUnbranched, filamentous alga found in

masses on the surfaces of standing water.

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Green Algae

– Multicellular UlvaStonewortsChara

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Green Algae

– Colonial Volvox

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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.SeaweedsKelpFucus

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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

Mader: Biology 8th Ed.

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 sicknessGiardia 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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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

Mader: Biology 8th Ed.

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.

Mader: Biology 8th Ed.

Review

• General Biology• Evolution• Diversity

– Green Algae– Red Algae– Brown Algae– Diatoms– Dinoflagellates

• Diversity– Euglenoids– Zooflagellates– Pseudopods– Ciliates– Sporozoans– Slime Molds– Water Molds

Mader: Biology 8th Ed.