Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Protists Chapter 35 Copyright © McGraw-Hill Companies Permission required for reproduction or display

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.

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies 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.

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies General Biology of the Protists Cell Surface  Possess varied array of cell surfaces. Locomotor Organelles  Chiefly flagellular rotation or pseudopodial movement. Cyst Formation  Dormant form of a cell with resistant outer covering in which metabolism is essentially shut down.

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies General Biology of the Protists  Nutrition - Employ all forms but chemoautotrophic.  Phototrophs  Heterotrophs  Phagotrophs - Visible food particles.  Osmotrophs - Food in soluble form.

General Biology of the Protists  Reproduction - Typically reproduce asexually.  Binary fission - Equal halves  Budding - Progeny cell smaller  Schizogomy - Multiple fission - In times of stress - sexual reproduction.  Gametic meiosis - Before gametes  Zygotic meiosis - After fertilization  Intermediary meiosis - Alternating

Five Groups of Protists

Protists are: Grouped according to shared characteristics: 1. Presence/Absence of cilia or flagella. 2. Presence and kinds of pigments. 3. Type of Mitosis. 4. Kinds of cristae in mitochondria. 5. Molecular genetics of ribosomal S subunit. 6. Inclusions 7. Overall body form. 8. Armor 9. Modes of nutrition and movement.

Heterotrophs with No Permanent Locomotor 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)

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.

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.

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.

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.

Photosynthetic Protists Chlorophyta: Green Algae  Extensive fossil record dating back 900 million years.  Mostly aquatic  Chlamydomonas is well-known genus. - Probably represents primitive state.

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.

Heterotrophs with Flagella Ciliophora: Ciliates, i.e. - paramecium  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.

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.

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

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.

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

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.

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

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.

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

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