Protists The Simplest Eukaryotes Chapter 22 Part 1
Impacts, Issues The Malaria Menace Plasmodium, a single-celled protist, causes malaria but also manipulates its mosquito and human hosts to maximize its own survival
22.1 The Many Protist Lineages Protists are eukaryotic organisms that are not fungi, plants, or animals Protists include many lineages of mostly singlecelled eukaryotes, some only distantly related to one another No single trait is unique to protists
Classification and Phylogeny
Fig. 22-2a, p. 352
Fig. 22-2b, p. 352
Fig. 22-2c, p. 352
Fig. 22-2d, p. 352
Fig. 22-2e, p. 352
Fig. 22-2f, p. 352
diplomonads parabasalids Flagellated Protozoans trypanosomes euglenoids prokaryotic ancestor radiolarians foraminiferans ciliates Alveolates dinoflagellates apicomplexans water molds diatoms Stramenopiles brown algae red algae chlorophyte algae Green charophyte algae Algae land plants amoebas Amoebozoans slime molds fungi choanoflagellates animals Fig. 22-2f, p. 352
Protist Organization and Nutrition Most protists are single-celled, but some are colonial or multicelled Protists can be autotrophs or heterotrophs, and a few can switch between modes Some single-celled protists can develop into a nonmotile, dormant cyst during hard times
Some Protist Characteristics
Three General Protist Life Cycles Protists show great diversity in life cycles; most reproduce both sexually and asexually Haploid-dominated life cycle (zygote is the only diploid cell) Alternation of generations (haploid and diploid multicelled forms) Diploid-dominated life cycle
Three General Protist Life Cycles
Fig. 22-3a, p. 353
zygote fertilization diploid (2n) haploid (n) meiosis gametes single cells or multicelled body spores mitosis Fig. 22-3a, p. 353
Fig. 22-3b, p. 353
zygote mitosis multicelled body fertilization diploid (2n) haploid (n) meiosis gametes multicelled body mitosis spores Fig. 22-3b, p. 353
Fig. 22-3c, p. 353
mitosis single cells or multicelled body zygote fertilization diploid (2n) haploid (n) meiosis gametes Fig. 22-3c, p. 353
fertilization gametes zygote diploid (2n) haploid (n) single cells or multicelled body meiosis spores mitosis mitosis zygote multicelled body fertilization gametes diploid (2n) haploid (n) multicelled body meiosis spores mitosis mitosis zygote fertilization single cells or multicelled body diploid (2n) haploid (n) meiosis gametes Stepped Art Fig. 22-3, p. 353
22.1 Key Concepts Sorting Out the Protists Protists include many lineages of single-celled eukaryotic organisms and their closest multicelled relatives Gene sequencing and other methods are clarifying how protist lineages are related to one another and to plants, fungi, and animals
22.2 Flagellated Protozoans Flagellated protozoans are single-celled 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
The Anaerobic Flagellates Diplomonads and parabasalids have multiple flagella and live in oxygen-poor waters Hydrogenosomes produce ATP anaerobically Some infect humans and cause disease Giardia lamblia is an intestinal parasite Trichomonas vaginalis causes a sexually transmitted disease
Giardia and Trichomonas
Fig. 22-4a, p. 354
Fig. 22-4b, p. 354
Fig. 22-4c, p. 354
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
Trypanosoma brucei
long flagellum attached to undulating membrane single, long mitochondrion Golgi body ER nucleus vacuole Fig. 22-5a, p. 354
red blood cell of human host flagellum attached to undulating membrane Fig. 22-5b, p. 354
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
A Euglenoid: Euglena gracilis
Fig. 22-6a, p. 355
flagellum 5 µm chloroplast nucleus mitochondrion Fig. 22-6a, p. 355
Fig. 22-6b, p. 355
chloroplast contractile vacuole eyespot ER nucleus pellicle Golgi body mitochondrion flagellum Fig. 22-6b, p. 355
Animation: Body plan of Euglena
22.3 Foraminiferans and Radiolarians Heterotrophic single cells with chalky or glassy shells live in great numbers in the world s oceans; cytoplasm extends through many pores
Chalky-Shelled Foraminiferans Foraminiferans are single celled protists that make calcium carbonate shells from CO 2 Helps stabilize atmospheric CO 2 levels and buffers ph of seawater Shells accumulate as chalk or limestone Most forams live on the seafloor; others drift as part of the plankton
White Cliffs of Dover Chalky remains of foraminiferans and other organisms with calcium-carbonate shells
Glassy-Shelled Radiolarians Radiolarians are heterotrophic protists with silica shells beneath their plasma membrane Most are part of the marine plankton vacuoles filled with air keep radiolarians afloat
22.2-22.3 Key Concepts Flagellated Protozoans and Shelled Cells Flagellated protozoans include single-celled predators and some human parasites Foraminiferans and radiolarians are shelled, single-celled heterotrophs; most live in seas