chapter 16. how ancient bacteria changed the world mounds of rock found near the bahamas contain...
TRANSCRIPT
How Ancient Bacteria Changed the World Mounds of rock found near the Bahamas Contain photosynthetic prokaryotes
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
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
Paleozoic
Meso-
zoic
Ceno-zoic
Humans
Land plants
Animals
Multicellulareukaryotes
Single-celledeukaryotes
Origin of solarsystem andEarth
1
2
4
3
Proterozoiceon
Archaeaneon
Billions of years
ago
Atmospheric oxygen
Prokaryotes
Figure 16.1C
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
Cooled watercontaining organic molecules
Cold water
Condenser
Sample forchemical analysis
H2O“Sea”
Water vapor“Atmosphere”
Electrode
CH4
NH3 H 2
Figure 16.3B
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
Fig. 19.6, p. 297
membrane-bound proto-cellslivingcells
self-replicating system enclosed in aselectively permeable, protective lipid sphere
DNA RNAenzymes andother proteins
formation ofprotein–RNA systems,
evolution of DNA
formation oflipid spheres
spontaneous formation of lipids,carbohydrates, amino acids, proteins,nucleotides under abiotic conditions
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
Self-replicating RNA acts astemplate on which poly-peptide forms.
Polypeptide acts as primitiveenzyme that aids RNAreplication.
RNA
Polypeptide
Figure 16.6A
Membranes may have separated various aggregates of self-replicating molecules Which could be acted on by natural selection
LM
65
0
Membrane
Polypeptide
RNA
Figure 16.6B, C
Origin of LifeHydrothermal Vent Life
http://www.youtube.com/watch?v=4LoiInUoRMQ
How Did Life Originate?http://www.youtube.com/watch?v=ozbFerzjkz4
Fig. 19.7a, p. 298-9
chemical and molecular evolution, first into self-replicating systems, then into membranesof proto-cells by 3.8 billion years ago.
In a second majordivergence, theancestors of archaebacteriaand of eukaryoticcells start downtheir separateevolutionaryroads.
The first majordivergencegives rise toeubacteria andto the commonancestor ofarchaebacteriaand eukaryoticcells.
Hydrogen-Rich, Anaerobic Atmosphere Oxygen in Atmosphere: 10%
3.8 billionyears ago
3.2 billionyears ago
2.5 billionyears ago
The amount of genetic informationincreases; cell size increases; thecytomembrane system and thenuclear envelope evolve throughmodification of cell membranes.
Cyclic pathway ofphotosynthesisevolves in someanaerobic bacteria.
Noncyclic pathwayof photosynthesis(oxygen-producing)evolves in somebacterial lineages.
Aerobic respiration evolvesin many bacterial groups.
ORIGIN OFPROKARYOTES
EUBACTERIALLINEAGE
ANCESTORS OFEUKARYOTES
ARCHAEBACTERIALLINEAGE
ARCHAEBACTERIA
Extreme halophiles
Methanogens
Extreme thermophiles
EUKARYOTESHeterotrophic protistans
EUBACTERIAOxygen-producing photosynthetic eubacteria (e.g., cyanobacteria)
Other photosynthetic eubacteria
Heterotrophic and chemoautotropic eubacteria
Fig. 19.7b, p. 298-9
(The ozone layer gradually develops) 20%
ORIGINS OF EUKARYOTESthe first protistans
ORIGINS OF ANIMALS
ORIGINS OF FUNGI
ORIGINS OF PLANTS
origin of mitosis, meiosis
ENDOSYMBIOTIC ORIGINS OF MITOCHONDRIA
ENDOSYMBIOTIC ORIGINS OF CHLOROPLASTS
Oxygen-producing photosynthetic eubacterium and early eukaryote become symbionts.
Aerobic species becomes endosymbiont of anaerobic forerunner of eukaryotess.
1.2 billionyears ago
900 millionyears ago
435 millionyears ago
present
ARCHAEBACTERIA
Extreme halophiles
Methanogens
Extreme thermophiles
EUKARYOTES
Animals
Heterotrophic protistans
Fungi
Photosynthetic protistans
Plants
EUBACTERIA
Oxygen-producing photosynthetic eubacteria (e.g., cyanobacteria)
Other photosynthetic eubacteria
Heterotrophic and chemoautotropic eubacteria