Page ‹#› Lynn Margulis the Ideas of the Endosymbiont Theory (Fig 25.9)
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In what ways are protists important? Base of many “food chains” - especially in aquatic settings The Protists Clarify water by filtering out small particles Some are parasites that cause A diverse assemblage of eukaryotes diseases in other organisms that ARENʼT Some have economic uses for humans fungi, plants, or animals Some are involved in important symbiotic relationships… Why can termites eat wood? And… they are a spectacular group Because of of organisms symbiotic hypermastigotes (a group of parabasilids) living in the termite gut working together with Archaean methanogens Fig 28.26 (SEM) Where Did Eukaryotic Cells come from? Origin of Organelles First found in fossil record about 2.1 Idea is that the ancestors of billion years ago eukaryotic cells were symbiotic consortiums of prokaryotic cells (Prokaryote fossils to 3.5 BYA) Two major features to explain: Has come to be called the “endosymbiont theory” - membrane-bounded organelles (mitochondria and plastids) - internal membrane systems Page ‹#› Lynn Margulis The Ideas of the Endosymbiont Theory (Fig 25.9) Mitochondria are the descendents of aerobic heterotrophic bacteria Chloroplasts are the descendants of photosynthetic bacteria - very likely cyanobacteria Person who led the development of the endosymbiont theory Evidence that Supports the Endosymbiont Theory Origin of Eukaryotes Endosymbiotic relationships exist in Fig.25.9 the modern world, e.g., some species of dinoflagellates are endosymbiotic in corals Plastids and mitochondria about the same size as typical prokaryotic cells Evidence (cont.) What organisms have eukaryotic cells? Similar membrane proteins (inner membrane) Animals (mitochondria) Reproduce by a process similar to Plants (mitochondria and plastids) binary fission Fungi (mitochondria) Contain circular DNA molecules Ribosomal RNA sequences in Protists (mitochondria, some have organelles more similar to plastids) prokaryotes Page ‹#› The Protists Flagella and Cilia (Fig 6.23) Incredible diversity of organisms - Structurally Human sperm your text recognizes 21 clades at distinct from probably the Phylum or Kingdom the flagella of level prokaryotes Typically found in aquatic or damp Eukaryotic flagella and Ciliate environments, or in body fluids, cilia have a tissues, or cells of host organisms similar Most have flagella or cilia at some structure stage in their life cycle involving microtubules Protist Size Cilia and Flagella in Action Most are single-celled, but their cell structure can be very complex Cilia and Flagella Ciliates (e.g., Paramecium, Vorticella) are among the most complex of all cells Some are multicellular and individuals can be as large as 60 meters in length - the “kelps” (brown algae) Kelp (Brown Algae) Protist Nutrition Nutritionally diverse - photoautotrophs - chemoheterotrophs Also are “mixotrophs” e.g., Euglena Definitely donʼt need a microscope to see this protist! Page ‹#› Nutrition Protistan Phylogeny “Kingdom Protista” was a diverse group of Three major means of obtaining organisms that were, in many cases, not nutrition amongst protists: closely related - Ingestive (“animal-like”), sometimes Phylogeny is currently in a “state of flux” called “protozoa” DNA sequence data have been, and will - Absorptive (“fungus-like”) continue to be, very helpful - Photosynthetic (“plant-like”), Splitting of “Kingdom Protista” into 21 clades (Phyla? Kingdoms?) has been sometimes called “algae” proposed Distinct nutritional mechanisms may be These clades have been placed into 5 found within one Clade “supergroups” in your text Fig 28.3 Protistan Diversity A quick look at 9 of the 21 protist clades described in Campbell et al. Supergroup Excavata Why not look at ALL 21 clades? Getting a Ph.D. - Thatʼs where you learn more and more about less and less until you know everything about nothing Evidence: Intro Bio Course - Thatʼs where you learn less and less about more and more until - Excavated feeding groove you know nothing about everything - DNA sequence similarities I want you to know something about Evidence supporting this “supergroup” is something... rather weak and investigation is on- going Page ‹#› The Parabasalids Trichomonas vaginalis (Fig. 28.4) Have modified mitochondria called “hydrogenosomes” Most familiar member Trichomonas vaginalis - cause of a common sexually transmitted disease Trichomonas Fact Sheet at the CDC Each cell possesses 4 flagella The Kinetoplastids The Euglenozoans One large mitochondrian per cell Organized mass of DNA inside the Two major groups: mitochondrian - called the “kinetoplast” the kinetoplastids Genus Trypanosoma the euglenids cause of “African sleeping sickness” Disease is vectored by the “Tsetse fly” (Glossina spp.) Invariably fatal if left untreated Tsetse Fly Fig. 28.6 Red blood cell Trypanosome Page ‹#› Supergroup Chromalveolata The Alveolates Characterized by the presence of small membrane-bounded cavities under their cell membrane Three major groups: Evidence: Dinoflagellates - DNA sequence similarities Apiocomplexans - Chloroplast structure similarities Ciliates Highly controversial “supergroup” The Dinoflagellates Dinoflagellates Both marine and freshwater Most species unicellular Important component of “plankton” About 50% of known species are photosynthetic Most species have elaborate cell Ceratium (light Peridinium walls microscope) (SEM) “Red Tide” Red Tide Dinoflagellate population explosions Water stained brownish-red (xanthophylls) Toxins produced by the dinoflagellates can kill fish, invertebrates, seabirds Some types of toxins can Boat accumulate in shellfish - causing Dead Fish poisoning in humans Page ‹#› Karenia brevis Karenia brevis (SEM) One species of dinoflagellate that causes red tides Produces a toxin that kills fish and invertebrates Human exposure to the toxin may cause a variety of symptoms, including death - Called “neurotoxic shellfish poisoning” Location of Karenia blooms Unit 1 Exam (data from December 2004) Available Monday 15 September through Tuesday 23 September READ: “COLL Testing Facility Policies and Procedures” in the Course Introduction Learning Module Go to Center for On-Line Learning, room 60 Carver Hall to take the exam The Cilates Ciliates Many beautiful freshwater species Use cilia to move and feed Have very complex cells, e.g., each cell has one micronucleus and one macronucleus Micronuclei participate in sexual reproduction; macronuclei in controlling cell functions Stentor spp. Paramecium spp. Page ‹#› The Stramenopiles Some species are photoautotrophic, Paramecium feeding some are heterotrophic Characterized by the presence hair- like projections on one of their (typically) two flagella Stramenopile Flagella (Fig 28.12) Four major groups: Diatoms Brown algae (includes “kelp”) Golden algae Oomycetes (water molds) Diatoms The Diatoms glass-like cell walls - made of hydrated silica Diatom Art important photosynthetic organisms in “plankton” fresh water and marine large number of species (estimated Diatom Diversity to be ~ 100,000) (Fig 28.3) Page ‹#› Diatomaceous Earth Supergroup Archaeplastida Huge amounts of ancient diatom cell walls Various uses: filtering medium metal polishes Evidence: reflective paint - DNA sequence similarity pesticide - Chloroplast structure similarities nanotechnology This “supergroup” is well supported SEM of Diatom by the available evidence The Red Algae Red Algae (Fig 28.19) No flagella present at any stage of the life cycle Most abundant in tropical oceans Most are multicellular ~ 6,000 described species Some species are heterotrophic Red Algae Human Uses Accessory Cell wall extracts: pigments allow carageenan - commonly photosynthesis eaten by people… at great depths - as deep as 260 agar - microbiological meters culturing media Effective at absorbing blue light Page ‹#› How do you feel about sushi? The Green Algae Most species (~7,000) found in fresh water Cell walls with a relatively high Fig. 28.19 percent of cellulose Can be unicellular, colonial/filamentous, or multicellular Can be motile (flagella) or non-motile Single-celled Green Alga - Chlamydomonas Eremosphaera viridis Chloroplasts Unicellular and motile green alga Nucleus Important model genetic system - much research is done with this organism Colonial Green Alga - Volvox (Fig. 28.3) Volvox Page ‹#› Filamentous Green Alga - Ulothrix spp. Multicellular Green Alga - Ulva spp. (Fig. 28.21) Green Algal Life Cycles An example of a green algal life cycle Can be quite complex with both sexual and asexual reproduction Oedogonium is a genus of Most gametes have two flagella filamentous green algae Gametes may be isogamous or anisogamous Some multicellular species exhibit alternation of generations (as do all plants) - may be heteromorphic or isomorphic Oedogonium Life Cycle Oedogonium life cycle Anisogamous Meiosis leads to production of “zoospores” (not gametes) Gametes are produced by mitosis Asexual “macrozoospores” are also produced by mitosis Page ‹#› Supergroup Unikonta The Amoebozoans Four major groups: Plasmodial slime molds Cellular slime molds Gymnamoebas (free-living) Evidence: - DNA sequence similarities Entamoebas (parasitic) This “supergroup” is well supported by the available evidence Plasmodial Slime Molds The plasmodium is a “coenocytic mass” Feeding stage is an called a Multinucleate “plasmodium” (Fig. 28.24) cytoplasm undivided by walls or membranes Live in moist habitats, e.g., rotting logs The plasmodium engulfs food by “phagocytosis” as do ameobas Cool Slime Mold Slime mold in “action” Planet Earth - Jungles 23:20 Page ‹#› Slime Mold Reproduction Response to the Environment