Chapter 22 The Protists 2 Outline Protist Biology

Chapter 22 The Protists

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

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

Origin of the Eukaryotic Cell 4

5 Ecology of 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

Protist Diversity 7

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 8

Green Algae: Chlamydomonas A minute (<25 μ m), 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 9

Electron Micrograph of Chlamydomonas 10

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 w “Spore” - a reproductive cell that develops into a new organism without fusing with another cell w “Zoospore” - flagellated spores, typical of aquatic species 11

Reproduction in Chlamydomonas 12

Green Algae: 13 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

Spirogyra 14

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 15

Multicellular Green Algae 16

Green Algae: Colonial Forms 17 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

Volvox 18

Diversity of Protists: Red Algae – The Rhodophyta 19 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

Red Algae 20

Diversity of Protists: Brown Algae – The Phaeophyta 21 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

Brown Algae 22

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 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

Diversity of Protists: Yellow-green Algae – The Chrysophyta 25 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

Diversity of Protists: Dinoflagellates – The Pyrrophyta 26 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

Diatoms and Dinoflagellates 27

Fish Kill and Dinoflagellate Bloom 28

Diversity of Protists: The Euglenoids – Phylum Euglenophyta 29 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

Euglena 30

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 31

Zooflagellates 32

Giardia lamblia 33

Diversity of Protists: Protists with Pseudopods 34 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

Protists with Pseudopods 35

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 36

Ciliates 37

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

Life Cycle of Plasmodium vivax 39

Diversity of Protists: Slime Molds 40 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

Plasmodial Slime Molds 41

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 42

Water Mold 43

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

Ending Slide Chapter 22 The Protists