1. Protists
Chapter 35
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2. Endosymbiosis
Theory of endosymbiosis proposes mitochondria originated as symbiotic, aerobic eubacteria.
Each mitochondrian still has its own genome in a circular, closed molecule of DNA.
Divide by simple fission.
Directed by nuclear genes.
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3. Artificial group of convenience. Single-celled organisms.
Classifying Protists
Protists are the most diverse of the four kingdoms in the domain Eukarya.
Artificial group of convenience.
Single-celled organisms.
Little consensus about protist classification.
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4. General Biology of the Protists
Cell Surface
- Possess varied array of cell surfaces.
Locomotor Organelles
flagellular rotation
pseudopodial movement
Cilia (short hairs covering the surface)
Cyst Formation
- Dormant form of a cell with resistant outer covering in which metabolism is essentially shut down.
Nutrition
Employ all forms but chemoautotrophic.
-Phototrophs
-Heterotrophs
--Phagotrophs - Visible food particles.
--Osmotrophs - Food in soluble form.
Reproduction
Typically reproduce asexually.
Sexual reproduction in times of stress.
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5. Five Groups of Protists
Group according to shared characteristics:
Presence/Absence of cilia or flagella.
Presence and kinds of pigments.
Type of Mitosis.
Kinds of cristae in mitochondria.
Molecular genetics of ribosomal S subunit.
Inclusions
Overall body form.
Armor
Modes of nutrition and movement.
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7. Heterotrophs with No Permanent Locomotion
Largest of the five general groups.
Three Principal Phyla
Rhizopoda: Amoebas
Move by pseudopods.
Actinopoda: Radiolarians
Secrete glassy exoskeletons.
Foraminifera: Forams
Pore-studded shells
Cytoplasmic projections (podia)
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8. Photosynthetic Protists
Pyrrhophyta: Dinoflagellates
Mostly unicellular photosynthetic organisms.
Distinctive flagella, protective coats, and biochemistry.
Zooxanthellae
Grow as symbionts within other cells lacking characteristic cellulose plates and flagella.
Produce primarily by asexual cell division.
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9. Dinoflagellates
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10. Photosynthetic Protists
Euglenophyta: Euglenoids
Most are freshwater.
About one-third are autotrophic.
Pellicle lies within membrane.
Stigma - Light sensitive organ that aids in orienting towards light.
Euglena
Two flagella attached to reservoir.
Contain numerous chloroplasts.
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12. Photosynthetic Protists
Chrysophyta: Diatoms and Golden Algae
Diatoms - Photosynthetic,unicellular organisms with double shells of opaline silica.
Divided into radial and bilateral symmetry.
Golden Algae - Named for yellow and brown carotenoid and xanthophyll accessory pigments in chloroplasts.
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13. Photosynthetic Protists
Rhodophyta: Red Algae
Colors results from phycobilin pigment, phycoerythrin.
Great majority of species occur in sea.
Interwoven filaments of cells.
Phaeophyta: Brown Algae
Multicellular protists, almost exclusively marine.
Kelp forests.
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14. Photosynthetic Protists
Chlorophyta: Green Algae
Extensive fossil record dating back 900 million years.
Mostly aquatic
Chlamydomonas is well-known genus.
Probably represents primitive state.
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16. Heterotrophs with Flagella
Zoomastigophora: Zoomastigotes
Unicellular, heterotrophic organisms highly variable in form.
Each has at least one flagellum.
Includes genera Trypanosoma (African Sleeping Sickness) and Crithidia, pathogens of human and domestic animals.
Giardia lamblia - Hiker’s Diarrhea.
Lives in upper intestine of host.
Spread by infected fecal matter.
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17. Heterotrophs with Flagella
Ciliophora: Ciliates
Most members have large numbers of cilia.
Usually arranged in longitudinal rows or in spirals around the body.
Micronuclei (mutligene chromosomes) or macronuclei (multiple copies of a certain gene).
Form vacuoles for ingesting food and regulating water balance.
Usually reproduce via transverse fission.
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19. Nonmotile Spore-Formers
Apiocomplexa: Sporozoans
Nonmotile, spore-forming animal parasites.
Complex life cycles that involve both asexual and sexual phases.
Malaria is caused by infection by sporozoan Plasmodium.
Three different stages of the Plasmodium life cycle each produce different antigens, and are sensitive to different antibodies.
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21. Heterotrophs With Restricted Mobility
Oomycota
Comprise water molds, white rusts, and downy mildews.
All are parasites or saprobes.
Life cycles characterized by gametic meiosis and a diploid phase.
Motile spores, zoospores, bear two unequal flagella.
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23. Heterotrophs With Restricted Mobility
Acrasiomycota: Cellular Slime Molds
Individual organisms behave as separate amobeas, moving through soil or other substrate and ingesting bacteria.
Individual organisms aggregate and form moving mass “slug”, that eventually transforms into a spore-containing mass sorocarp.
Develops stalk and releases spores.
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25. Heterotrophs With Restricted Mobility
Myxomycota: Plasmodial Slime Molds
Stream along as a non-walled, multinucleate mass of cytoplasm, plasmodium.
Produces sporangium during times of resource shortage.
Forms spores that quickly undergo meiosis.
Multiple nuclei in each spore disintegrate, leaving each spore with a single haploid nucleus.
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