The Origin and Evolution of Microbial Life: Prokaryotes and

Protists

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

PaleozoicMeso-

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-cells livingcells

self-replicating system enclosed in aselectively permeable, protective lipid sphere

DNA RNA enzymes 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

Fig. 19.11, p. 301

DNA

infolding of plasma membrane

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

Fossilized prokaryote and a living bacterium

Figure 16.1Dx1

Origin of Life

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

ARCHAEBACTERIAExtreme 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

ARCHAEBACTERIAExtreme halophiles

Methanogens

Extreme thermophiles

EUKARYOTESAnimals

Heterotrophic protistans

Fungi

Photosynthetic protistans

Plants

EUBACTERIAOxygen-producing photosynthetic eubacteria (e.g., cyanobacteria)

Other photosynthetic eubacteria

Heterotrophic and chemoautotropic eubacteria