Prokaryotes and Protists
CH 16
PROKARYOTESProkaryotes have inhabited Earth for billions of years– Prokaryotes are the oldest life-forms and remain the
most numerous and widespread organisms
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SEM
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Figure 16.7
• 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
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
ProkaryotesSmall, relatively simple cells
• Do not have a membrane-bound nucleus
Figure 4.3B
Branches of Prokaryote Evolution
Bacteria and Archaea– Distinguished on the basis of nucleotide
sequences and other molecular and cellular features
Prokaryote Shapes
• Cocci• Bacilli• Spirochetes
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
Structural Features
• Capsule• Pili• Flagella
Growth & Reproduction
• Binary Fission• Endospore
Innards
• Lacks membrane bound organelles• Respiratory / photosynthetic membrane• Small, circular genome• Ribosomes
Nourishment
• Phototrophs & Chemotrophs• Autotrophs & Heterotrophs• Biofilms
CO2
Organiccompounds
Energy source
Chemical
ChemoautotrophsPhotoautotrophs
ChemoheterotrophsPhotoheterotrophs
Light
Carbonsource
Archea Extremes
• Extremophiles– Halophiles– Thermophiles
• Methanogens
Bacteria• Proteobacteria• Chlamydias• Spirochetes• Gram-positive bacteria• Cyanobacteria
Disease
• Exotoxins• Endotoxins
Bacteria Uses
• Biological weaponry• Bioremediation
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
Protists are an extremely diverse assortment of mostly unicellular eukaryotes
The parasitic Giardia
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Red blood cell
Apex
TEM
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000
Plasmodium causes malaria
SEM
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Single celled algae
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
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
Protists
• Diplomanads– Parabasalids
• Euglenozoans• Alveolates– Dinoflagellates– Ciliates– Apicomplexans
Protists• Stramenopiles– Watermolds– Diatoms– Brown Algae
• Amoebozoans– Feed via pseudopodia– Plasmodial slime mold• Plasmodium
– Cellular slime molds
Protists
• Foraminiferans• Radiolarians• Algae– Red– Green
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