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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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

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Plasmodium causes malaria

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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