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Protist diversity II

Protist diversity II. Level 1 Biological Diversity Jim Provan. Phylogeny of eukaryotes. Diplomonads and Parabasala. Amitochondriate: Originally believe to have diverged before acquisition of mitochondria Presence of nuclear gene homologues now suggests that mitochondria have been lost

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Protist diversity II

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  1. Protist diversity II Level 1 Biological Diversity Jim Provan

  2. Phylogeny of eukaryotes

  3. Diplomonads and Parabasala • Amitochondriate: • Originally believe to have diverged before acquisition of mitochondria • Presence of nuclear gene homologues now suggests that mitochondria have been lost • Diplomonads have multiple flagella and two separate nucleii • Infectious

  4. Euglenozoa • Contain flagella • Two main groups: • Euglenoids: • Paramylon (glucose polymer) used as a storage molecule • Anterior pocket with one or two flagella • Kinetoplastids: • Contain a single large mitochondrion and a unique organelle (kinetoplast) • Symbiotic / pathogenic

  5. Alveolata • Encompasses: • Photosynthetic flagellates (dinoflagellates) • Parasites (apicomplexans) • Group that move by cilia (ciliates) • Have small, membrane-bound cavities under cell surfaces (alveoli)

  6. Dinoflagellates • Components of phytoplankton – may cause red tides • Most are unicellular, some are colonial • Some are photosynthetic symbionts, some are non-photosynthetic parasites • Plastids are brownish and contain chlorophylls a and c and a mix of carotenoids (including peridinin) • Food stored as starch • Chromosomes lack histones and are always condensed • Have no mitotic stages

  7. Apicomplexans • All parasites of animals: • Infectious cells called sporozites • Apex of sporozites has organelles for penetrating host cells • Life cycles have both sexual and asexual reproduction, often requiring more than one host • Several species of Plasmodium cause malaria: • Anopheles mosquitoes serve as intermediate host • New, resistant forms of Plasmodium are appearing • Little success in developing a vaccine: • Plasmodium spends most of its life cycle in blood or liver cells • Has the ability to alter its surface antigens

  8. Life history of Plasmodium

  9. Ciliates • Species use cilia to move and feed • Most solitary cells in fresh water • Cilia are short and beat in synchrony • Submembraneous system coordinates beating • Some species move on leg-like cirri • Others have rows of tightly packed cilia which act as locomoter membranelles • Among most complex of cells

  10. Two types of ciliate nuclei • Macronucleus: • Is large and has over 50 copies of the genome • Genes packaged into units, each with hundreds of copies of just a few genes • Controls everyday functions by synthesising RNA • Necessary for asexual reproduction – macronucleus elongates and splits instead of undergoing mitosis • Micronucleus: • Small and present in 1-80 copies • Does not function in growth, maintenance or asexual reproduction • Functions in the sexual process of conjugation

  11. Conjugation and genetic recombination in Paramecium

  12. Stramenopiles • Includes several heterotrophic groups as well as a variety of photosynthetic protists (algae): • Oomycota (water moulds etc.): • Heterotrophic • Ostensibly similar to fungi but have analogous hyphae, cellulose cell walls (as opposed to chitin), prevalent diploid stage and biflagellated cells (true fungi have no flagellated stages) • Heterokont algae: • Diatoms have hydrated silica shells and generally reproduce asexually • Chrysophytes (golden algae) have carotene and xanthophyll accessory pigments and are mostly unicellular • Phaeophytes (brown algae) are all multicellular and mostly marine

  13. Seaweeds • Have differentiated tissues and organs similar to plants: • Analogous: • Holdfast  root • Stipe  stem • Blade  leaf • Commercially important: • Food (Laminaria and Porphyra) • Agar • Thickeners • Lubricants

  14. Alternation of generations in algae

  15. Rhodophyta (red algae) • Have no flagellated stages • Accessory pigment: phycoerythrin • Not always red: dependent on depth • Mostly multicellular • Diverse life cycles but alternation of generations is common

  16. Chlorophyta (green algae) • Two main groups: • Chlorophyceae • Charophyceae • Share a common ancestor with green plants • Unicellular, colonial or multicellular • Nearly all reproduce sexually by way of biflagellated gametes

  17. Life cycle of Chlamydomonas

  18. Rhizopods (amoebas) • Simplest unicellular protists • No flagellated stages • Pseudopodia used in feeding and movement • All reproduction is asexual • Inhabit freshwater, marine and soil habitats • Most are free living, although some are parasitic

  19. Actinopods • Possess axopodia, slender form of pseudopodia • Increase surface area which helps floating and feeding • Some prey may stick to axopodia and be phagocytosed • Two main groups: • Heliozoans (primarily freshwater) • Radiolarians (primarily marine)

  20. Plasmodial slime moulds (Myxomycota)

  21. Cellular slime moulds (Acrasiomycota)

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