Page ‹#› The Protists A diverse assemblage of eukaryotes that ARENʼ T fungi, plants, or animals In what ways are protists important? Base of many “food chains” - especially in aquatic settings Clarify water by filtering out small particles Some are parasites that cause diseases in other organisms Some have economic uses for humans Some are involved in important symbiotic relationships… Why can termites eat wood? Because of symbiotic hypermastigotes (a group of parabasilids) living in the termite gut working together with Archaean methanogens Fig 28.26 (SEM) And… they are a spectacular group of organisms Where Did Eukaryotic Cells come from? First found in fossil record about 2.1 billion years ago (Prokaryote fossils to 3.5 BYA) Two major features to explain: - membrane-bounded organelles (mitochondria and plastids) - internal membrane systems Origin of Organelles Idea is that the ancestors of eukaryotic cells were symbiotic consortiums of prokaryotic cells Has come to be called the “endosymbiont theory”
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The Protists Tapps.dso.iastate.edu/si/...2008/...Protists_Lect_6.pdf · Protist Size Most are single-celled, but their cell structure can be very complex Ciliates (e.g., Paramecium,
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The Protists
A diverse assemblage of eukaryotesthat ARENʼT
fungi, plants, or animals
In what ways are protists important?
Base of many “food chains” - especiallyin aquatic settings
Clarify water by filtering out smallparticles
Some are parasites that causediseases in other organisms
Some have economic uses for humansSome are involved in important
symbiotic relationships…
Why can termites eat wood?
Because ofsymbiotichypermastigotes(a group ofparabasilids) livingin the termite gutworking togetherwith Archaeanmethanogens Fig 28.26 (SEM)
And… they are a spectacular groupof organisms
Where Did Eukaryotic Cells come from?
First found in fossil record about 2.1billion years ago
(Prokaryote fossils to 3.5 BYA)Two major features to explain:
- membrane-bounded organelles(mitochondria and plastids)
- internal membrane systems
Origin of Organelles
Idea is that the ancestors ofeukaryotic cells were symbioticconsortiums of prokaryotic cells
Has come to be called the“endosymbiont theory”
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Lynn Margulis
Person who led the development of the endosymbiont theory
The Ideas of the EndosymbiontTheory (Fig 25.9)
Mitochondria are the descendents ofaerobic heterotrophic bacteria
Chloroplasts are the descendants ofphotosynthetic bacteria - very likelycyanobacteria
Origin ofEukaryotes
Fig.25.9
Evidence that Supports theEndosymbiont Theory
Endosymbiotic relationships exist inthe modern world, e.g., somespecies of dinoflagellates areendosymbiotic in corals
Plastids and mitochondria about thesame size as typical prokaryoticcells
Evidence (cont.)
Similar membrane proteins (innermembrane)
Reproduce by a process similar tobinary fission
Contain circular DNA moleculesRibosomal RNA sequences in
organelles more similar toprokaryotes
What organisms have eukaryotic cells?
Animals (mitochondria) Plants (mitochondria and plastids) Fungi (mitochondria) Protists (mitochondria, some have
plastids)
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The ProtistsIncredible diversity of organisms -
your text recognizes 21 clades atprobably the Phylum or Kingdomlevel
Typically found in aquatic or dampenvironments, or in body fluids,tissues, or cells of host organisms
Most have flagella or cilia at somestage in their life cycle