Transcript The Origin and Evolution of Microbial Life: Prokaryotes

Chapter 16
How Ancient Bacteria Changed the World
 Mounds of rock found near the Bahamas

Contain photosynthetic prokaryotes
 Stromatolites in northern Canada
Figure 16.0Ax1
 Fossilized mats 2.5 billion years old mark a time when
photosynthetic prokaryotes

Were producing enough O2 to make the atmosphere aerobic
Layers of a bacterial mat
 Bacterial mats
Figure 16.0Ax2
EARLY EARTH AND THE ORIGIN OF
LIFE
 The early atmosphere probably contained

H2O, CO, CO2, N2, PO43- and some CH4
 Volcanic activity, lightning, and UV radiation were intense
Figure 16.1A
 A clock analogy tracks the origin of the Earth to the
present day
 And shows some major events in the history of
Earth and its life
Cenozoic
Humans
Land plants
Origin of solar
system and
Earth
Animals
4
1
Proterozoic
eon
Multicellular
eukaryotes
Archaean
eon
3
2
Prokaryotes
Single-celled
eukaryotes
Figure 16.1C
Atmospheric
oxygen
16.2 How did life originate?
 Organic molecules

May have been formed abiotically in the conditions on early
Earth
Miller – Urey Experiment
 Simulations of such conditions

Have produced amino acids, sugars, lipids, and the
nitrogenous bases found in DNA and RNA
Water vapor
CH4
“Atmosphere”
Electrode
Condenser
Cold water
H2O
“Sea”
Figure 16.3B
Cooled water
containing
organic
molecules
Sample for
chemical analysis
16.4 The first polymers may have formed on hot rocks or
clay
 Organic polymers such as proteins and nucleic acids

May have polymerized on hot rocks
living
cells
membrane-bound proto-cells
self-replicating system enclosed in a
selectively permeable, protective lipid sphere
DNA
RNA
formation of
protein–RNA systems,
evolution of DNA
enzymes and
other proteins
formation of
lipid spheres
spontaneous formation of lipids,
carbohydrates, amino acids, proteins,
nucleotides under abiotic conditions
Fig. 19.6, p. 297
16.6 Membrane-enclosed molecular co-ops may have
preceded the first cells
 RNA might have acted as templates for the formation of
polypeptides

Which in turn assisted in RNA replication
Self-replication of RNA
RNA
Self-replicating RNA acts as
template on which polypeptide forms.
Polypeptide
Figure 16.6A
Polypeptide acts as primitive
enzyme that aids RNA
replication.
DNA
infolding of
plasma
membrane
Fig. 19.11, p. 301
 Membranes may have separated various aggregates of self-
replicating molecules

Which could be acted on by natural selection
Membrane
LM 650
RNA
Figure 16.6B, C
Polypeptide
 Fossilized prokaryote and a living bacterium
Figure 16.1Dx1
Origin of Life
Origin of Life
Hydrothermal Vent Life
http://www.youtube.com/watch?v=4LoiInUoRMQ
How Did Life Originate?
http://www.youtube.com/watch?v=ozbFerzjkz4
Hydrogen-Rich, Anaerobic Atmosphere
Oxygen in Atmosphere: 10%
ARCHAEBACTERIA
Extreme halophiles
ARCHAEBACTERIAL
LINEAGE
Methanogens
Extreme thermophiles
In a second major
divergence, the
ancestors of
archaebacteria
and of eukaryotic
cells start down
their separate
evolutionary
roads.
chemical
and molecular
evolution, first
into selfreplicating
systems,
then into
membranes
of proto-cells
by 3.8
billion years
ago.
EUKARYOTES
Heterotrophic protistans
ANCESTORS OF
EUKARYOTES
The first major
divergence
gives rise to
eubacteria and
to the common
ancestor of
archaebacteria
and eukaryotic
cells.
ORIGIN OF
PROKARYOTES
3.8 billion
years ago
The amount of genetic information
increases; cell size increases; the
cytomembrane system and the
nuclear envelope evolve through
modification of cell membranes.
Cyclic pathway of
photosynthesis
evolves in some
anaerobic bacteria.
Noncyclic pathway
of photosynthesis
(oxygen-producing)
evolves in some
bacterial lineages.
EUBACTERIA
Oxygen-producing photosynthetic
eubacteria (e.g., cyanobacteria)
Other photosynthetic eubacteria
EUBACTERIAL
LINEAGE
Aerobic respiration evolves
in many bacterial groups.
3.2 billion
years ago
Heterotrophic and
chemoautotropic eubacteria
2.5 billion
years ago
Fig. 19.7a, p. 298-9
(The ozone layer gradually develops) 20%
ARCHAEBACTERIA
Extreme halophiles
Methanogens
Extreme thermophiles
ORIGINS OF ANIMALS
ORIGINS OF EUKARYOTES
the first protistans
EUKARYOTES
Animals
Heterotrophic protistans
origin of
mitosis,
meiosis
ORIGINS OF FUNGI
Fungi
Photosynthetic protistans
Plants
ENDOSYMBIOTIC ORIGINS OF
MITOCHONDRIA
ORIGINS OF PLANTS
ENDOSYMBIOTIC ORIGINS OF
CHLOROPLASTS
Oxygen-producing photosynthetic
eubacterium and early eukaryote
become symbionts.
EUBACTERIA
Oxygen-producing photosynthetic
eubacteria (e.g., cyanobacteria)
Other photosynthetic eubacteria
Heterotrophic and
chemoautotropic eubacteria
Aerobic species becomes endosymbiont of
anaerobic forerunner of eukaryotess.
1.2 billion
years ago
900 million
years ago
435 million
years ago
present
Fig. 19.7b, p. 298-9