Mader: Biology 8th Ed.

The Protists

Mader: Biology 8th Ed.

Outline

• General Biology• Evolution• Diversity

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

• Diversity Protozoans

– Euglenoids– Zooflagellates– Pseudopods– Ciliates– Sporozoans

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 (multicellular).

– Autotrophs and heterotrophs– Aquatic environment– Asexual reproduction is common, but sexual

reproduction can occur when the environment becomes stressful.

Spores Cysts

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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 2 anterior flagella Eyespot Usually reproduces asexually

Forms spores and zoospores when growth conditions are unfavorable.

Mader: Biology 8th Ed.

Mader: Biology 8th Ed.

Green Algae– Spirogyra

found in masses on the surfaces of standing water like lakes and ponds.

called pond scum Unbranched, filamentous Helical chloroplast Conjugation Algal bloom

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Green Algae– Multicellular

Filamentous Mostly marine

Ulva (sea lettuce)

Edible Green Algae

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Caulerpa lentilliferaC. racemosa

Codium reediae

Chlorella sp.

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Red Algae

• Red Algae (phylum Rhodophyta)– Multicellular– warmer seawater– Accessory pigment phycobilins

(phycoerythrin)– Cell walls with calcium

carbonate (corralline algae)

Economic ImportanceAgar and carrageen

Edible Red Algae

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Porphyra sp.

Gelidium sp. (agar)Chondrus crispus (carrageen)

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Brown Algae

• Brown Algae (phylum Phaeophyta)– chlorophylls a and c – carotenoid pigments: fucoxanthin and xanthophyll– Laminarin– Often observed on rocky coasts in north

temperate zone. Largest Seaweeds Kelps (Laminaria) Fucus Macrocystis

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Brown Algae

Mader: Biology 8th Ed.

The Diatoms

• Diatoms (phylum Bacillariophyta) are the most numerous unicellular algae in the oceans– Significant phytoplankton– Cell wall has outer layer of silica.– Cell wall composed of two valves, with the

larger valve acting as a lid.– Various shapes of their silicious tests or

cell wall

Economic Importance of Diatoms

• Sources of food and O2 for heterotrophs

• deposits of these shells used as filtering aids, abrasives, cleansers, and paints

• world's oil and gasoline supply comes from diatom fossil beds

• toothpaste • Environmental indicators of pollution

Mader: Biology 8th Ed.

DIATOMS

Mader: Biology 8th Ed.

Mader: Biology 8th Ed.

The Dinoflagellates

• Phylum Pyrrophyta • Unicellular and phytoplanktons• Usually bounded by protective cellulose plates

impregnated with silicates• Typically contain two flagella• Photosynthetic with chloroplasts vary in color• Usually reproduce asexually• Some genera may cause red tide• Produce neurotoxins

Mader: Biology 8th Ed.

Dinoflagellates

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The Euglenoids

• Microscopic freshwater unicellular organisms• Have two flagella and an eyespot

(photoreceptor for detecting light)• Bound by flexible pellicle• Chloroplast and pyrenoid• Longitudinal cell division asexual reproduction

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Euglena

Mader: Biology 8th Ed.

Mader: Biology 8th Ed.

The Zooflagellates

• Zooflagellates (phylum Zoomastigophora) are colorless heterotrophs.

• Most are symbiotic and parasitic– Well known for causing various diseases in

humans.African sleeping sickness ( Trypanosoma,

vector tsetse fly)Giardia lamblia ( contaminated water)Trichonomas vaginalis (sexually transmitted

Mader: Biology 8th Ed.

Zooflagellates

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Protists with Pseudopods

• Pseudopods form when cytoplasm streams forward in a particular direction.

– Amoeboids (phylum Rhizopoda) move and ingest their food with pseudopods

Phagocytize food– Foraminiferans (phylum Foraminifera)- skeleton

or test made of calcium carbonate – Radiolarians (phlyum Actinopoda)- have

siliceous tests.

Protists with Pseudopods

Mader: Biology 8th Ed.

The Ciliates

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

– Hundreds of cilia beat in coordinated rhythm.– Pellicle contain trichocysts– Most are holozoic ( ingest and digest solid food)– Divide by transverse binary fission during asexual

reproduction.– Macronucleus and micronucleus– Sexual reproduction ( conjugation)

- High level of diversity

Ciliates

Paramecium Conjugation1. Two paramecium individuals come in contact on their oral surface.2. The micronuclei divide by meiosis to produce four haploid micronuclei.3. Three micronuclei degenerate4. The remaining micronucleus divides to form male and female pronuclei5. Syngamy occurs6. Male micronuclei are exchanged between conjugants.

7. Male and female pronuclei fuse and individuals separate8. Old macronuclei are absorbed and replaced by new macronuclei

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