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Chapter 29 - PROTISTS_freeman

Chapter 29 - PROTISTS_freeman - Chapter 29 ­ PROTISTS...

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Unformatted text preview: Chapter 29 ­ PROTISTS Chapter 29 ­ PROTISTS All eukaryotes that are not plants, fungi or animals. Summary *General characteristics of protists. *Why they are important? *How are protists studied? *Diversity and evolutionary advances. *Key lineages. General Characteristics *The first eukaryotes *Unicellular or colonial or “multicellular” *Habitats are wet or moist *Very diverse kingdom *Occur in high abundance *Paraphyletic group – i.e. do not include all of the descendents of a common ancestor. Importance *Cause diseases in plants and animals *Algal blooms – red tides infect marine life *Many are primary producers: *Act as a “Carbon (CO2) Sink” ***Global Warming *Diseases, Table 29.1 *Plasmodium – malaria *Trichomonas – trichomoniasis (STD) *Giardia – Giardiasis *Amoeba – amoebic dynsentery *Phytophthora – potato blight How are Protists Studied? *Phylogeny is based on: * Cell structure – nuclear envelope and other organelles classify them as eukaryotes. * rRNA and other genes are analyzed to divide the Kingdom into smaller groups. * Morphology, behavior and reproduction cycles are used to further classify 1 the kingdom. the kingdom. *Fig 29.8 – note position of fungi, plants and animals. Evolutionary Advances *Protists offer a clue to the origin of mitochondria and chloroplasts and perhaps other cell organelles. *Endosymbiosis Theory, fig 29.11 *An ancient eukaryote engulfs a bacterial cell *Instead of being digested the bacteria and host cell develop a “mutualistic” relationship. *Endosymbiosis *The host cell provides carbon for the bacteria and the bacteria provides ATP for the host. *The bacterial cell (proteobacteria) evolves into a mitochondria. *Chloroplasts are believed to have originated in the same way when cyanobacteria were engulfed by ancient eukaryotic cells. What is the Evidence that Supports the Endosymbiosis Theory? * of mitochondria and chloroplasts Size *Mitochrondria and chloroplasts reproduce by binary fission *Unique ribosomes and proteins *Double membranes *Some chloroplasts have peptidoglycans in outer membrane, all have chlorophyll a like cyanobacteria *Have their own genomes (circular piece of DNA) and can replicate themselves. Evolutionary Advances Cont’d *What do protists tell us about the evolution of eukaryotes? * Cells became larger. * Organelles or compartments developed. (Ex. Mitochondria, chloroplasts, lysosomes, peroxisomes, Golgi apparatus, ER, etc.) Evolutionary Advancements *What do protists tell us about the evolution of eukaryotes? 2 *Compartments also require some support or organization – cytoskeletons develop. *Protists include unicellular organisms, colonial organisms and primitive multicellular organisms. Multicellularity is an analogous trait among Eukaryotes. Diversity of Protists * Protection and support *Cell walls * Tests (shells) of cellulose, CaCO3, or SiO2 *Rigid internal skeletons *Feeding habits * Ingestive feeding: * Absorptive feeding: * Photosynthesis *Movement *Cell crawling ­ pseudopodia *Swimming * Cilia * Flagella – different action compared with bacteria *Both cilia and flagella have the same molecular structure and occur throughout the eukaryotic domain. *Reproduction *Alternating asexual and sexual cycles in many protists. *Sexual reproduction requires a haploid stage. *Different multicellular forms represent the haploid (gametophyte) and diploid (sporophyte) stages. In some, the haploid stage dominates, in others the diploid stage dominates. *Figs. 29.20 & 29.21 Key Lineages * Excavata ­ ?oldest protists, parasites that have lost their mitochondria. 2 groups: *Diplomonadida (2 nuclei) – *Giardia *Parabasalida (1 nucleus) – *Trichomonas 3 * Euglenida (Discicristata): unicellular, ½ are photosynthetic, eyespots, flagella **Euglena, *Trypanosoma * Alveolata – unicellular; 3 groups * Ciliata: 2 nuclei, cilia – *Paramecium * Dinoflagellata: cellulose skeletons, ½ are photosynthetic – red tides, “sparkling” waves * Apicomplexa: parasites – *Plasmodium (malaria) * Stramenopila – uni­ and multicellular, “hairy flagella” are unique. * Oomycota: cell walls of cellulose – potato blight. * Diatoms: silicone shells – diatomaceous earth * Phaeophyta: photosynthetic, brown algae (kelp) * Amoebozoa ­ no cell walls *Amoeba and slime molds * Foraminifera ­ CaCO3 tests *“Shelled amoebas” ­ chalk (White Cliffs of Dover), marble and limestone; oil deposits *Plantae? *Rhodophyta: red algae *Chlorophyta: green algae 4 ...
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