Prokaryotes and Protists
CH 16
PROKARYOTES
Prokaryotes have inhabited Earth for billions of years
Colorized SEM 650 
– Prokaryotes are the oldest life-forms and remain the
most numerous and widespread organisms
Figure 16.7
First Cells
• RNA might have acted as templates for the
formation of polypeptides
– Assisted in RNA replication
Self-replication of RNA
RNA
Self-replicating RNA acts as
template on which polypeptide forms.
Polypeptide
Polypeptide acts as primitive
enzyme that aids RNA
replication.
Membranes may have separated various aggregates of selfreplicating molecules which could be acted on by natural
selection
Membrane
LM 650
RNA
Figure 16.6B, C
Polypeptide
Prokaryotes
Small, 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
Energy source
Light
CO2
Photoautotrophs
Chemical
Chemoautotrophs
Carbon
source
Photoheterotrophs Chemoheterotrophs
Organic
compounds
Archea Extremes
• Extremophiles
– Halophiles
– Thermophiles
• Methanogens
Bacteria
•
•
•
•
•
Proteobacteria
Chlamydias
Spirochetes
Gram-positive bacteria
Cyanobacteria
Disease
• Exotoxins
• Endotoxins
Bacteria Uses
• Biological weaponry
• Bioremediation
Bioremediation
Recycle chemicals and clean up the environment
– Prokaryotes are decomposers in
• Sewage treatment and can clean up oil spills and toxic
mine wastes
Rotating
spray arm
Rock bed
coated with
aerobic
bacteria
and fungi
Liquid wastes
Figure 16.16A, B
Outflow
Protists are an extremely diverse assortment of
mostly unicellular eukaryotes
The parasitic Giardia
SEM 2,300
Single celled algae
Apex
Red blood cell
TEM 26,000
Colorized SEM 4,000 
Plasmodium causes malaria
Protists and Evolution
• Multicellularity evolved in several different
lineages probably by specialization of the cells
of colonial protists
Gamete
Locomotor
cells
2
1
Somatic
cells
3
Foodsynthesizing
cells
Unicellular protist
Colony
Early multicellular organism
with specialized, interdependent cells
Later organism that
produces gametes
Symbiosis
• Endosymbiosis
• Secondary endosymbiosis
Green alga
Nucleus
Remnant of
green alga
Secondary
endosymbiosis
Chloroplast
Euglenozoans
Cyanobacterium
Primary
endosymbiosis
Nucleus
Heterotrophic
eukaryote
Autotrophic
eukaryotes
Heterotrophic
eukaryotes
Remnant of
red alga
Dinoflagellates
Evolved into
chloroplast
Secondary
endosymbiosis
Nucleus
Chloroplast
Apicomplexans
Red alga
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