Outline

1. The Protists

2. Protist Biology Protist Evolution Protist Diversity Green Algae Red Algae Brown Algae Diatoms Dinoflagellates Protist Diversity, cont. Euglenoids Zooflagellates Pseudopods Ciliates Sporozoans Slime Molds Water Molds Outline

3. General Biology of the Protists • Classified into the Domain Eukarya & the Kingdom Protista • Morphology: • Most unicellular • Many with amazingly high level of strucrural and functional complexity • Life cycles: • Asexual reproduction common • Sexual reproduction may occur when conditions deteriorate • Some life cycles simple, many extremely complex

4. Origin of the Eukaryotic Cell

5. Ecology of Protists • Protists are of enormous eco-logical importance • Photoautotrophic forms: • Produce oxygen • Function as producers in both freshwater and saltwater ecosystems • Major component of plankton • Organisms that are suspended in the water • Serve as food for heterotrophic protists and animals • Many protists are symbionts • Ranges from strict parasitism to mutualism • Coral reefs greatly aided by symbiotic photoautotrophic protists in tissues of corals

6. Evolution of Protists • Complexity and diversity of protists makes them difficult to classify • Many classification schemes proposed • None has broad support • Cannot be classified as plants, animals, or fungi • Could be split into as many as a dozen kingdoms • The scheme chosen for this discussion is based on modes of nutrition

7. Protist Diversity

8. Diversity of Protists:Green Algae – The Chlorophyta • Phylum Chlorophyta • Approximately 7,500 species • Inhabit a variety of environments including oceans, freshwater, snowbanks, tree bark, and turtles backs • Many are symbionts with fungi, plants, or animals • Morphology varied • Majority unicellular, but many are filamentous or colonial • Some are multicellular and resemble leaves of lettuce • Plants thought to be derived from Chlorophyta because both groups: • Have a cell wall that contains cellulose • Possess chlorophylls a and b, and • Store excess food as starch

9. Green Algae:Chlamydomonas • A minute (<25 μm), actively moving flagellate • Inhabits still, freshwater pools • Fossil ancestors date back over a billion years • Anatomy: • Definite cell wall • Single, large, cup-shaped chloroplast • Chloroplast with a pyrenoid where starch is synthesized • Many with a bright red eyespot, or stigma on chloroplast • Two long, whip-like flagella • Project from the anterior end • Operate with a breaststroke motion

10. Electron Micrograph of Chlamydomonas

11. Green Algae:Chlamydomonas • Most often reproduces asexually • As many as 16 daughter cells within parent cell • Escape by digesting the parent cell • Occasionally reproduces sexually • Gametes fuse to form a zygote • Becomes a heavy-walled, resistant zygospore • Goes into a period of dormancy • Upon germination produces four zoospores by meiosis • “Spore” - a reproductive cell that develops into a new organism without fusing with another cell • “Zoospore” - flagellated spores, typical of aquatic species

12. Reproduction in Chlamydomonas

13. Green Algae:Spirogyra • Filamentous green algae • Found in green masses on the surfaces of ponds and streams • Has ribbon-like, spiraled chloroplasts • Sexual reproduction by conjugation: • A temporary union during which the cells exchange genetic material • Two filaments line up parallel to each other • Cell contents of one filament move into the cells of the other filament • Forms diploid zygospores • In spring, undergo meiosis to produce new haploid filaments

14. Spirogyra

15. Green Algae:Multicellular Forms • Ulva • Multicellular green alga • Commonly called sea lettuce • Thallus (body) is two cells thick • Can be as much as a meter long • Sexual cycle involves alternation of generations • Similar to higher plants, except • Both generations look exactly alike, and • The gametes all look the same

16. Multicellular Green Algae

17. Green Algae:Colonial Forms • Volvox • A colony is a loose association of independent cells • A Volvox colony: • A hollow sphere • Thousands of cells arranged in a single layer surrounding a watery interior • Each cell of colony resembles a Chlamydomonas cell • Flagella beat in a coordinated fashion • Some cells are specialized for reproduction • Each can divide asexually to form a new daughter colony within the parental colony • Leaves parental colony by releasing an enzyme that dissolves away a portion of the parental colony

18. Volvox

19. Diversity of Protists:Red Algae – The Rhodophyta • Multicellular • About 5,000 species • Live mostly in warmer seawater, some as deep as 200 m • Economic Importance • Agar - capsules; dental impressions; cosmetics; culture medium; electrophoresis; food prep. • Carrageen - an emulsifying agent used in chocolate, low-fat foods, & cosmetics • The reddish-black wrappings around sushi rolls consist of processed Porphyra blades

20. Red Algae

21. Diversity of Protists:Brown Algae – The Phaeophyta • About 1,500 species • Most live in colder ocean waters along rocky coasts • No unicellular or colonial brown forms • Morphology: • Some small forms with simple filaments • Others large multicellular forms that may exceed 200 m in length • Pigments: • Chlorophylls a and c • Fucoxanthin (a type of carotinoid pigment) gives them their color • Excess food stored as a carbohydrate called laminarin

22. Brown Algae

23. The Phaeophyta • Multicellular forms of green, red, and brown algae are called seaweeds • Laminaria (a kelp), and Fucus, (rockweed), are common intertidal seaweeds • Nereocystis and Macrocystis often form forest-like thickets in deeper waters • Sargassum forms floating masses where other organisms find shelter • Harvested for food and fertilizer • Macrocystis is source of algin, a thickener for foods

24. The Phaeophyta • Laminaria shows tissue differentiation • Transport organic nutrients in a tissue resembling phloem • Life cycle • Most brown algae have alternation of generations • In some species of Fucus • Meiosis produces gametes instead of spores • The adult is always diploid, as in animals

25. Diversity of Protists:Yellow-green Algae – The Chrysophyta • Diatoms (formerly Bacillariophyta) are the most numerous unicellular algae in the oceans • Significant portion of phytoplankton • Cell wall • Two valves, with the larger valve acting as a lid (like a mint tin) • Contains silica • Diatomaceous earth used as • Filtering agents • Sound-proofing materials • Polishing abrasives

26. Diversity of Protists:Dinoflagellates – The Pyrrophyta • About 4,000 species of unicellular aquatic and marine organisms • Morphology: • Cell is usually bounded by protective cellulose plates impregnated with silicates • Typically with two flagella • One in a longitudinal groove with its distal end free • The other lies in a transverse groove that encircles the organism • Symbiotic dinoflagellates in corals called zooxanthellae • Dinoflagellates provide their host with organic nutrients • Corals provide wastes that fertilize the algae • Some lack chloroplasts and are parasitic • Gymnodinium brevis may cause “red tide” • Produce a powerful neurotoxin that has caused massive fish kills • Consume shellfish during outbreak can cause respiratory paralysis

27. Diatoms and Dinoflagellates

28. Fish Kill and Dinoflagellate Bloom

29. Diversity of Protists:The Euglenoids – Phylum Euglenophyta • Small freshwater unicellular organisms • Difficult to classify • Have two flagella and an eyespot (shades a photoreceptor) • One flagellum much longer than the other • Projects out of an anterior, vase-shaped invagination • Called a tinsel flagellum because of hair-like projections • Cell bounded by flexible pellicle • Chloroplasts: • Surrounded by three rather than two membranes • With a pyrenoid which produces an unusual type of carbohydrate called paramylon

30. Euglena

31. Diversity of Protists:Zooflagellates – Phylum Zoomastigophora • Colorless heterotrophs • Most symbiotic and many parasitic • Well known for causing various diseases in humans • Trypanosoma • African sleeping sickness - Tsetse fly • Chagas disease – Kissing bug • Giardia lamblia • Most common flagellate in human digestive tract • Causes severe diarrhea • Cysts are transmitted in contaminated water • Beavers are important reservoir hosts • Trichomonas vaginalis • Sexually transmitted protist, • Infects urogenital organs; a common cause of vaginitis

32. Zooflagellates

33. Giardia lamblia

34. Diversity of Protists: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 • Entamoeba histolytica - a parasite of the human colon; • Causes amoebic dysentery • Can be fatal • Foraminiferans (phylum Foraminifera) and radiolarians (phlyum Actinopoda) • Both have a skeleton (test) of either calcite or silica

35. Protists with Pseudopods

36. Diversity of Protists:The Ciliates – Phylum Ciliophora • Ciliates (phylum Ciliophora) are among the most complex of the protozoans • Hundreds of cilia beat in coordinated rhythm • Most are holozoic, swallowing food whole • Divide by transverse binary fission during asexual reproduction • Two nuclei of differing types • Micronucleus – Heredity • Macronucleus – Metabolism

37. Ciliates

38. Diversity of Protists:The Sporozoans – Phylum Apicomplexa • Nonmotile obligate parasites • Most serious parasitic disease of human is malaria • Plasmodium spp • Kills 3,000,000 people each year • Transmitted by mosquito • Toxoplasma • Humans get from cats • Causes birth defects and mental retardation when pregnant mom exposed

39. Life Cycle of Plasmodium vivax

40. Diversity of Protists:Slime Molds • Plasmodial Slime Molds - Phylum Myxomycota • Body in the form of a plasmodium • Diploid, multinucleated, cytoplasmic mass • Enveloped by a slimy sheath • Eventually produces sporangium which in turn produces spores • Cellular Slime Mold - Phylum Acrasiomycota • Body in the form of individual amoeboid cells • Later aggregate into pseudoplasmodium which then forms sporangium & spores

41. Plasmodial Slime Molds

42. Diversity of Protists:Water Molds - Phylum Oomycota • Most live in the water • Phylum name refers to the enlarged tips (called oogonia) where eggs are produced • Body filamentous, appearing like true Fungi • Cell walls largely of cellulose rather than chitin • The organism is diploid (not haploid as in the fungi) • Phytophthora infestans caused the 1840’s potato famine in Ireland • Saprolegnia is often seen as a white, cotton-like coating on dead aquarium fish

43. Water Mold

44. Protist Biology Protist Evolution Protist Diversity Green Algae Red Algae Brown Algae Diatoms Dinoflagellates Protist Diversity, cont. Euglenoids Zooflagellates Pseudopods Ciliates Sporozoans Slime Molds Water Molds Review

45. The Protists