Prokaryotes and Protists
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Transcript of Prokaryotes and Protists
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Prokaryotes and Protists
CH 16
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PROKARYOTESProkaryotes have inhabited Earth for billions of years– Prokaryotes are the oldest life-forms and remain the
most numerous and widespread organisms
Colo
rized
SEM
650
Figure 16.7
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• RNA might have acted as templates for the formation of polypeptides – Assisted in RNA replication
First Cells
Self-replication of RNA
Self-replicating RNA acts astemplate on which poly-peptide forms.
Polypeptide acts as primitiveenzyme that aids RNAreplication.
RNA
Polypeptide
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Membranes may have separated various aggregates of self-replicating molecules which could be acted on by natural selection
LM 6
50
Membrane
Polypeptide
RNA
Figure 16.6B, C
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ProkaryotesSmall, relatively simple cells
• Do not have a membrane-bound nucleus
Figure 4.3B
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Branches of Prokaryote Evolution
Bacteria and Archaea– Distinguished on the basis of nucleotide
sequences and other molecular and cellular features
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Prokaryote Shapes
• Cocci• Bacilli• Spirochetes
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Structural Features• Gram staining– Cell wall differences
• Gram + (purple)– Simple cell wall– Thick peptidogylcan layer
• Gram – (pink)– More complex cell wall with lipids bonded to
carbohydrates– Thin peptidoglycan layer
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Structural Features
• Capsule• Pili• Flagella
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Growth & Reproduction
• Binary Fission• Endospore
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Innards
• Lacks membrane bound organelles• Respiratory / photosynthetic membrane• Small, circular genome• Ribosomes
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Nourishment
• Phototrophs & Chemotrophs• Autotrophs & Heterotrophs• Biofilms
CO2
Organiccompounds
Energy source
Chemical
ChemoautotrophsPhotoautotrophs
ChemoheterotrophsPhotoheterotrophs
Light
Carbonsource
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Archea Extremes
• Extremophiles– Halophiles– Thermophiles
• Methanogens
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Bacteria• Proteobacteria• Chlamydias• Spirochetes• Gram-positive bacteria• Cyanobacteria
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Disease
• Exotoxins• Endotoxins
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Bacteria Uses
• Biological weaponry• Bioremediation
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BioremediationRecycle chemicals and clean up the environment– Prokaryotes are decomposers in• Sewage treatment and can clean up oil spills and toxic
mine wastes
Figure 16.16A, B
Liquid wastes Outflow
Rotatingspray arm
Rock bed coated withaerobicbacteriaand fungi
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Protists are an extremely diverse assortment of mostly unicellular eukaryotes
The parasitic Giardia
Colo
rized
SEM
4,0
00
Red blood cell
Apex
TEM
26,
000
Plasmodium causes malaria
SEM
2,3
00
Single celled algae
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Protists and Evolution • Multicellularity evolved in several different
lineages probably by specialization of the cells of colonial protists
Unicellular protist Colony Early multicellular organismwith specialized, interdepen-dent cells
Later organism thatproduces gametes
Food-synthesizingcells
Locomotorcells
Somaticcells
Gamete
1 2 3
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Symbiosis• Endosymbiosis• Secondary endosymbiosis
Nucleus
Primaryendosymbiosis
Cyanobacterium
Heterotrophiceukaryote
Evolved intochloroplast
Autotrophiceukaryotes
Nucleus
Nucleus
Chloroplast
Green alga
ChloroplastRed alga
Heterotrophiceukaryotes
Secondaryendosymbiosis
Secondaryendosymbiosis
Remnant ofgreen alga
Euglenozoans
Remnant ofred alga
Dinoflagellates
Apicomplexans
Stramenopiles
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Protists
• Diplomanads– Parabasalids
• Euglenozoans• Alveolates– Dinoflagellates– Ciliates– Apicomplexans
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Protists• Stramenopiles– Watermolds– Diatoms– Brown Algae
• Amoebozoans– Feed via pseudopodia– Plasmodial slime mold• Plasmodium
– Cellular slime molds
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Protists
• Foraminiferans• Radiolarians• Algae– Red– Green