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Protist diversity I

Protist diversity I. Level 1 Biological Diversity Jim Provan. Diversity of protists. In Whittaker’s five-kingdom system, eukaryotes were divided into four of the five kingdoms: Animalia Fungi Plantae Protista

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Protist diversity I

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  1. Protist diversity I Level 1 Biological Diversity Jim Provan

  2. Diversity of protists • In Whittaker’s five-kingdom system, eukaryotes were divided into four of the five kingdoms: • Animalia • Fungi • Plantae • Protista • Kingdom Protista originally contained all eukaryotes that did not fit into one of the other three kingdoms: • Mostly microscopic, single-celled organisms • Extremely diverse • Paraphyletic

  3. Protist diversity

  4. Animals Plants Fungi Early diversification of eukaryotes Paraphyly of protists

  5. Protist diversity • Nutrition: • Mostly aerobic and use mitochondria • May be photoautotrophic, heterotrophic or mixotrophic • Different modes scattered throughout different lineages • Motility • Life cycles: • Asexual, sexual and syngamous • Can form cysts • Habitat: • Mostly aquatic: plankton and phytoplankton • Symbionts

  6. The chloroplast • Carries out photosynthesis • Contains own genome • Believed to be of endosymbiotic origin • Phylogenetically related to cyanobacteria

  7. The mitochondrion • Primary site of oxidative phosphorylation • Contains own genome • Gene sequences suggest closest relationship with -proteobacteria • Believed to be of endosymbiotic origin

  8. Compartmentalisation of the eukaryotic cell

  9. Serial endosymbiosis • Explains evolution of mitochondria and plastids • Theory proposes ancestral endosymbiosis (one cell living inside another): • Mitochondria derived from a-proteobacteria • Chloroplasts derived from cyanobacteria • Either undigested prey or internal parasites • Some eukaryotes lack chloroplasts but most have mitochondria: suggests that mitochondria evolved first

  10. Evidence for the theory of serial endosymbiosis • Other endosmbiotic relationships are successful! • Morphological similarity: appropriate size • Membranes contain similar enzymes • Replicate by binary fission • Single, circular genome • Bacteria-like ribosomes and tRNAs • DNA evidence (?)

  11. Secondary endosymbiosis • Several taxonomic groups have plastids: • Plants • Chlorophytes s.s. (Chlamydomonas) • Rhodophytes s.s. (Porphyra) • Glaucocystophytes (Cyanophora) • Chlorarachniophytes (Chlorarchnion) • Euglenids (Euglena) • Cryptomonads (Guillardia) • Haptophytes (Emiliana) • Heterokonts (Laminaria, Phytophthora) • Dinoflagellates (Amphidinium) • Apicomplaxans (Plasmodium) • [Ciliates (Paramecium)]

  12. Rhodophytes Chlorophytes Glaucocystophytes Algal lineages Primary (Double membrane) Secondary (Three or more membranes) Cryptophytes Heterokonts Haptophytes Dinoflagellates Apicomplexans Euglenoids Chlorarachniophytes

  13. Eukaryotes and the “big picture” of evolution

  14. Eukaryote phylogeny

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