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Protist diversity I

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In Whittaker's five-kingdom system, eukaryotes were ... Mostly aquatic: plankton and phytoplankton. Symbionts. The chloroplast. Carries out photosynthesis ... – PowerPoint PPT presentation

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Title: Protist diversity I


1
Protist diversity I
  • Level 1 Biological Diversity
  • Jim Provan

2
Diversity of protists
  • In Whittakers 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
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
Algal lineages
Primary (Double membrane) Secondary (Thre
e 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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