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Kingdom Protista The Link Between Bacteria and the Multicellular World • There are plant-like protists that photosynthesize – – – – Dinoflagellates Euglena Diatoms Algae The Link Between Bacteria and the Multicellular World • Some are carnivorous protists that are hunters – Amoebas – Ciliates The Link Between Bacteria and the Multicellular World • Finally, some are like fungus, because they absorb nutrients from the surroundings and produce spores. – Slime molds. Protist: Characteristics • All are Eukaryotic • Some motile, some not • Some single-celled, some multicellular. • Variety of Ways to Get Energy – Some are • Carnivorous • Photosynthetic • Chemoautotrophic • Detritivores Characteristics • Reproduction – Primarily Asexual • Budding • Fragmentation • Spores – Sexual (less common but does happen) • Many events happen in times of stress • Male + Female gametes • Sometimes, protists Protista: General Characteristics Classification and Phylogeny prokaryotic ancestor diplomonads Flagellated parabasalids Protozoans trypanosomes euglenoids radiolarians foraminiferans ciliates Alveolates dinoflagellates apicomplexans water molds diatoms Stramenopiles brown algae Figure 22.2 Single-celled protists include (a) amoebas, (b) euglenoids, and (c) diatoms. Most red algae (d) and all brown algae (e) are multicelled. (f) One proposed eukaryotic family tree with traditional protist groups indicated by tan boxes. Notice that the protists are not united as a single lineage. Figure It Out: Are land plants more closely related to the red algae or the brown algae? Answer: red algae red algae chlorophyte algae Green charophyte algae Algae land plants amoebas Amoebozoans slime molds fungi choanoflagellates animals Group: Flagellated Protozoans • Flagellated protozoans are singlecelled protists covered by a pellicle (proteins that help cells retain shape) • They swim in lakes, seas, and the body fluids of animals • They are typically heterotrophic and reproduce asexually by binary fission Trypanosomes and Other Kinetoplastids • Kinetoplastids are flagellated protozoans with a single large mitochondrion • Trypanosomes include human pathogens that are transmitted by insects – African sleeping sickness (T. brucei) is spread by tsetse flies – Chagas disease (T. cruzi) is spread by bloodsucking bugs Human Disease Trypanosoma •African sleeping sickness •Transmitted by tsetse fly •Causes fever, mental deterioration and coma •No means of locomotion- most are parasitic and don’t need it •Sexual reproduction present •Environmentparasitic-aquatic Phylum Zoomastigina Human Disease Giardia •Causes giardiasis •Sever diarrhea and intestinal cramps •Parasite in contaminated water •Thousands of cases annually in U.S. A SEM micrograph of the small intestine of a gerbil infested with Giardia reveals a mucosa surface almost entirely obscured by attached trophozoites •Not usually fatal, but, you can imagine, uncomfortable. The Euglenoids • Euglenoids are flagellated protists related to kinetoplastids that do not infect humans – Most prey on bacteria – Some have chloroplasts that evolved from green algae and can detect light with an eyespot – Most live in freshwater and have contractile vacuoles that expel excess water Foraminiferans & Radiolarians • Heterotrophic single cells with chalky or glassy shells live in great numbers in the world’s oceans; cytoplasm extends through many pores. • Most forams live on the seafloor; others drift as part of the plankton. Phylum Actinopoda • Radiolarians • Silica test • Pseudopodia used for food getting • Asexual reproduction • Mostly marine Phylum Foraminifera Forams •Locomotion and food getting by pseudopodia •Calcium carbonate test •Environmentprimarily marine Group: Alveolates/ Ciliates • Ciliates are heterotrophic single cells that move about with the help of cilia • Ciliates reproduce asexually by binary fission or sexually by conjugation. Phylum Ciliophora • Locomotion and food getting by cilia • Pellicle present maintains shape • Contractile vacuoles remove excess water • Sexual reproduction by conjugation • Environmentaquatic • Heterotrophic & parasitic Paramecium •Unicellular •Heterotrophic •Cilia •Requires oxygen to live = aerobic environment •Asexual & Sexual Reproduction •Special Quality 2 nucleii •Found in most aquatic environments Phylum Ciliophora Stentor •Largest freshwater protozoan •Can regenerate body parts •Cilia covers body for movement & feeding Phylum Ciliophora Didinium This organism is aggressive and has a huge appetite Didinium feeding Attaches to paramecium Starts to ingest Almost completely engulfed Phylum Apicomplexa •Protozoan that causes malaria •Plasmodium enters bloodstream, travels to liver cells, where they divide and release new spores into the bloodstream. •Parasitic •No locomotion •Reproduce asexually •Transmitted by bite of infected mosquito •Destroys red blood cells Group: Stramenopiles • “Red Algae” • Brown algae are multi-celled protists that live in temperate or cool seas; ranging from microscopic filaments to giant kelp • Some brown algae are used commercially – Thickeners (algins), food, fertilizer, herbal supplements (bladderwrack) Diatoms • Diatoms are singlecelled or colonial protists that have a two-part silica shell – Shells accumulate on the seafloor (diatomaceous earth) • Most are photosynthetic, with a brown accessory pigment (fucoxanthin) – Major components of phytoplankton Group: Red Algae • Red algae are mostly multicelled marine algae that live in clear, warm waters • Red accessory pigments (phycobilins) allow red algae to live at greater depths than other algae • Red and green algae share a common ancestor with chloroplasts derived from cyanobacteria • Life cycles vary and are often complex, with both asexual and sexual phases; there is no flagellated stage. Group: Green Algae • Most green algae are chlorophytes – Chlorella: Single celled, grown as health food – Chlamydomonas: Single celled, freshwater alga – Volvox: Colonial, freshwater alga – Cladophora: Forms long filaments – Ulva: “Sea lettuce” – Codium fragilis: Branching marine alga • Charophyte algae include several lineages that form a clade with land plants – Desmids: A single-celled, freshwater group – Spirogyra: Forms long filaments – Stoneworts (Chara): Closely related to land plants Group: Amoebozoans • Amoebozoans send out pseudopods, move about, and capture food – Most have no cell walls, shell, or pellicles • Amoebas live as single cells – Example: Amoeba proteus, a freshwater predator • Slime molds are “social amoebas” – Plasmodial and cellular slime molds • Plasmodial slime molds spend most of their lives as a plasmodium – A streaming multinucleated mass that feeds on microbes and organic matter – Undergoes mitosis many times without cell division – Develops into spore-bearing fruiting bodies Phylum: Sarcodina • Unicellular • Have pseudopodia = “false foot” which is an extension of the cytoplasm • Pseudopodia for locomotion & feeding • Reproduce asexually • Most are free-living, some parasitic • Found in soil, marine and freshwater Amoebas Amoeba Structure Amoeba locomotion & feeding • Endocytosis (Phagocytosis) • Digestion by enzymes • Distinguish between food and non-food Recap • Protists represent the kingdom where evolutionary adaptations allowed for the development of plants, fungus, and animals from single-celled bacteria. • Protists have numerous characteristics that allow for grouping. • Some protists are good for us: provide nutrients, photosynthesize, etc. • Some protists cause disease: malaria, African sleeping sickness, giardiasis.
![Algae are photosynthetic protists [1].](http://s1.studyres.com/store/data/017042472_1-57660ad2cb7ef6aa961a43cb9146e4af-150x150.png)
