Protists

Protists Overview Overview Eukaryotic cells Eukaryotic cells Unicellular to multicellular Unicellular to multicellular Autotrophs and heterotrophs Autotrophs and heterotrophs Asexual reproduction by mitosis Asexual reproduction by mitosis

Protists Ecological Importance Ecological Importance Aquatic protists give off oxygen and function as producers Aquatic protists give off oxygen and function as producers Part of plankton and serve as food for heterotrophs Part of plankton and serve as food for heterotrophs

Protists Classification Classification By modes of nutrition By modes of nutrition Autotrophs – ex. Algae Autotrophs – ex. Algae Heterotrophs – ex. Protozoans Heterotrophs – ex. Protozoans

Protists Green algae Green algae Variety of environments Variety of environments Most unicellular Most unicellular Contain chlorophylls a and b Contain chlorophylls a and b

Protists Green algae Green algae Chlamydomonas Chlamydomonas Unicellular Unicellular Freshwater Freshwater Single, large chloroplast that contains a pyrenoid Single, large chloroplast that contains a pyrenoid 2 flagella 2 flagella Asexual reproduction, sexual reproduction if unfavorable conditions Asexual reproduction, sexual reproduction if unfavorable conditions

Chlamydomonas

Protists Green algae Green algae Spirogyra Spirogyra Filamentous, unbranched Filamentous, unbranched Aquatic Aquatic Ribbon-like, spiralled chloroplasts Ribbon-like, spiralled chloroplasts Sexual reproduction - conjugation Sexual reproduction - conjugation

Spirogyra

Protists Multicellular green algae Multicellular green algae Ulva (Sea lettuce) Ulva (Sea lettuce) Marine Marine Alternation of generations life cycle Alternation of generations life cycle Chara (Stoneworts) Chara (Stoneworts) Freshwater Freshwater Male and female parts on same or separate individuals Male and female parts on same or separate individuals Most closely related to plants Most closely related to plants

Ulva Chara

Protists Multicellular green algae Multicellular green algae Volvox Volvox Colonial, flagellated Colonial, flagellated Cells cooperate by coordinating beat of flagellae Cells cooperate by coordinating beat of flagellae Some cells specialized for reproduction Some cells specialized for reproduction

Volvox

Protists Red Algae Red Algae Marine Marine Most are multicellular with filamentous branches Most are multicellular with filamentous branches Commercially important – ex. agar Commercially important – ex. agar

Protists Brown Algae Brown Algae Marine Marine Multicellular, can be very large Multicellular, can be very large Kelp and Fucus (rockweed) Kelp and Fucus (rockweed) Commercially important Commercially important Laminaria – transport system resembles phloem Laminaria – transport system resembles phloem

Protists Diatoms Diatoms Unicellular, marine and freshwater Unicellular, marine and freshwater Significant part of phytoplankton Significant part of phytoplankton Consists of 2 valves, resembles a hat box Consists of 2 valves, resembles a hat box Reproduce asexually until 30% of original size then reproduce sexually Reproduce asexually until 30% of original size then reproduce sexually Cell wall of silica Cell wall of silica

Protists Dinoflagellates Dinoflagellates Aquatic and marine, unicellular producers Aquatic and marine, unicellular producers Protected by plates containing silicates Protected by plates containing silicates 2 flagella 2 flagella Some capable of bioluminescence Some capable of bioluminescence Sexual and asexual reproduction Sexual and asexual reproduction

Figure 22.10b

Protists Euglenoid Euglenoid Freshwater, unicellular Freshwater, unicellular Some have chloroplasts, some do not Some have chloroplasts, some do not 2 flagella – one much longer than the other 2 flagella – one much longer than the other Eyespot Eyespot Contractile vacuole Contractile vacuole Reproduce by longitudinal division, no sexual reproduction Reproduce by longitudinal division, no sexual reproduction

Euglena

Protists Zooflagellates Zooflagellates Mostly unicellular and heterotrophic Mostly unicellular and heterotrophic Symbiotic and parasitic Symbiotic and parasitic Types Types Trypanosomes – transmitted by the bite of the tsetse fly, cause African Sleeping sickness Trypanosomes – transmitted by the bite of the tsetse fly, cause African Sleeping sickness Giardia lamblia – found in fresh water, causes severe diarrhea Giardia lamblia – found in fresh water, causes severe diarrhea Trichomonas vaginalis – sexually transmitted Trichomonas vaginalis – sexually transmitted

Trypanonsoma

Giardia lamblia

Trichomonas vaginalis

Protists Protists with Pseudopods Marine and freshwater, unicellular Part of zooplankton Amoeboids Ingest algae, bacteria, or other protists by phagocytosis Freshwater forms have contractile vacuole

Protists Protists with Pseudopods Foraminiferans and radiolarians Skeleton is called a test Foraminiferan test – calcium carbonate and often multichambered, external Radiolarian test – silica, internal, usually with spines Dead organisms form deep layer of sediment on ocean floor

Figure 22.15b

Protists Ciliates Most structurally complex and specialized of all protozoa Unicellular, most free-living Move by cilia

Protists Ciliates Paramecium Ponds and ditches Cilia project through pellicle that contains trichocysts Holozoic – food particles swept down gullet and digested in food vacuoles Reproduction – transverse binary fission and sexual by conjugation Macro- and micronuclei

Protists Sporozoans Nonmotile, parasitic, and spore-forming Pneumocystis Pneumonia in immunocompromised patients Cysts in pulmonary sacs, release spores when mature which develop into mature organisms

Protists Sporozoans Plasmodium Cause malaria Life cycle alternates between sexual and asexual phases in different hosts Asexual stage in humans Sexual stage in mosquito

Protists Sporozoans Toxoplasma gondii Causes toxoplasmosis Found in cats, venison Can lead to birth defects and neurological symptoms in AIDS patients

Protists Slime and water molds Decomposers, also feed on bacteria Parasite of plants and animals Ingest food by phagocytosis

Protists Plasmodial slime molds One enormous single cell with thousands of nuclei, formed when individual flagellated cells fuse Creeps along phagocytizing decaying plant material During unfavorable times develops many sporangia, spores can survive until conditions favorable again

Protists Cellular slime molds Exist as amoeboid cells Common in soil, feed on bacteria and yeasts In unfavorable conditions organism aggregates to form pseudoplasmodium and fruiting bodies containing spores form

Protists Water molds Form furry growths on fishes and insects One species responsible for the potato famine in Ireland in 1840s

Figure 22.19