1. Origin of Life

2. Eons – largest time division
Eons determined by major changes in the Earth
Most recent Eon started with the appearance of multicellular animals = Phanerozoic Eon
Three Eons make up what was previously know as the Precambrian Period
1) Proterozoic
2) Archean
3) Hadean

3. I. WHEN Did Life Evolve?
A) Earth molten for Hadean Eon (4.5 – 3.9 bya)
B) cooled by 3.9 billion years ago
C) Solid rock formation began Archean Eon 3.9 bya

4. II. First life likely formed in water
A) water vapor condenses and falls as rain
B) Creates oceans
C) salts added over billions of years as material eroded from continents
D) water protects from U-V radiation

5. III. First cell = anaerobic conditions
A) Early Archean rock dark-colored = unoxidized
B) Formed before free O2 available
C) oxidized (rusted) sediment appears 2.2 billion years ago in Proterozoic Eon
D) Free oxygen produced by living cells doing .…
photosynthesis
E) Therefore, life must have evolved before 2.2 bya

6. IV. How did the first cell form?
A) Spontaneous formation of monomers and
macromolecules from
chemicals in environment
**** Only possible if no free O2
B) cell membranes form
C) nucleic acids pass on
Genetic infromation

7. V. Monomer Synthesis
A. we created organic monomers from non-living chemicals
B.Miller and Urey - created
“Early Earth Apparatus”
C. Archaean atmosphere
D. electrodes produce “lightning”
E. primordial pond in the bottom

8. F. Results: 12 of 20 most common amino acids synthesized + monomers
Showed monomers can form from non-living source
next step: polymerization

9. VI. Requirements for polymerization
A. energy source:
1. lightning 2. geothermal vents
B. concentration: to bring materials together
1. tide pools/evaporation
2. clay

10. clay a. Forms platelets b. platelets are: very small flat
with negative charge on surface

11. VII. Cell membrane formation
A) phospholipids amphipathic
hydrophobic & hydrophilic
B) form spheres in water
C) hydrophobic ends protected on
inside
D) First cell membrane?

12. VIII. Protobionts/protocells
A) fatty acid spheres form naturally
B) Macromolecules & enzymes inside
C) reactions occur inside
D) Grow
E) divide
F)selectively permiable
G) digest starch
H) store & release energy

13. Experiments by Sidney W. Fox and Sidney w
Experiments by Sidney W. Fox and Sidney w. Fox and Aleksandr Oparin have demonstrated that protobionts form spontaneously. They formed liposomes and microspheres, which have membrane structure similar to the phospholipid bilayer found in cells may be formed spontaneously, in conditions similar to the environment thought to exist on an early Earth. These experiments formed

14. I. Are Protobionts Alive?
1)No
2) they can’t replicate themselves
(pass on their traits to offspring)

15. IX. Replication
A) process by which organisms make genetic copies of themselves
asexual reproduction
2) sexual reproduction

16. X. Origin of Heredity A) many different types of protobionts
B) those best able to accumulate organic molecules, grow, and divide become most common
C) but “competition” is useless unless traits can be passed on/inherited
D) need polymers that can replicate themselves: DNA and RNA

17. XI. Nucleic acid reproduction
A) RNA can assemble on its own (Zn catalyst)
B) Can replicate (make more copies)
C) Can pass on genetic info when cell divides
D) RNA world Hypothesis

18. XII. Earliest Life Forms 3.5 bya
3.4 byo, South Africa
A) prokaryotic bacteria
B) anaerobic: live without O2
C) fermenters:
use organic molecules for energy
modern

19. XIII. The First Energy Crunch
A) organic molecules become scarce
B) competitive advantage goes to –
C) organisms that can make their own food
Photosynthesis
D) done by primitive cyanobacteria

20. Photosynthesis
1) light-absorbing pigments (like chlorophyll) already present
2) chlorophyll rings form
spontaneously
3) mutation causes e- to jump out
4) leads to Anaerobic cyclic psyn
Makes only a little ATP (no glucose)

21. Aerobic Non-cyclic Photosynthesis
some cyanobacteria evolved to use H2O as e- source
O2 released as a by-product
Advantage: glucose produced = storable energy
Problem: O2 toxic to anaerobic cells
6CO H2O
carbon
dioxide
water
C6H12O O2
sugar
oxygen
energy from sunlight

22. Indirect (non-fossil) evidence
Build up of oxygen
Indirect (non-fossil) evidence
for the presence of
cyanobacteria ~ 3.5 bya

23. BIFs (Banded Iron Formations)
Indirect evidence for the presence of
cyanobacteria ~ 3.5 bya
Precambrian,
Australia

24. Banded Iron Formations Created
iron dissolves in anaerobic water
when iron bonds to O2 it becomes solid
Iron oxide deposited in red layers
When dissolved iron used up :
1) cyanobacteria die
2) dark, un-oxidized layers build up

25. Why are BIFs Banded? When runoff added more Fe to the water the entire process stared over again.

26. What Likely Happened O2 made by cyanobacteria at ocean surface
O2 toxic to them
but not if the O2 was removed by bonding with iron (Fe)
Oceans contained dissolved iron

27. BIFs began forming 3.5 bya = 1st free O2
ended about 1.8 bya = constant free O2

28. Earliest (Undisputed) Fossils = Stromatolites
2.2 byo Michigan

29. Stromatolites dome-shaped, layered structures Up to 3.5 byo
consist of layers of bacteria
upper layers aerobic, photosynthetic
lower layers anaerobic
produce abundant oxygen
how do we know?

30. They are still alive today in special environments, notably Shark Bay, Australia
Tide In
Tide Out

31. Formation of Stromatolites
Cyanobacteria form a mat
on top of sediment
A new layer of sediment
is deposited on top
1 cm
Bacteria grow up
through new layer

32. Stromatolites provide evidence for the
occurrence of cyanobacteria in the fossil record.
Modern
Ancient

33. Aerobic Bacteria some bacteria evolved antioxidants
allowed them to survive rising O2 levels by 1.8 bya
some evolved to use O2…
= aerobic respiration
Obligate anaerobe bacteria restricted to refuges or go extinct

34. The rise of cyanobacteria & build up of oxygen in atmosphere had three significant effects:
Aerobic photoautotrophs became producers that fuel the food chains of surface world
The first mass extinction
oxygen-rich atmosphere set stage for the multicellular life (aerobic respiration)

35. Eukaryotic Cells First well established fossils 1.7 bya
Mid-Proterozoic eon
Early protists
unicellular
with nucleus
100x larger
than bacteria

37. Origin of Nucleus & E. R. In-folding of cell membrane
Similar to bacterial psyn membrane
Surrounded DNA
Formed ER

38. Endomembrane system and nuclear envelope are continuous

39. ‘In eukaryotes the organelles of the endomembrane system include: the nuclear membrane, the endoplasmic reticulum, the Golgi apparatus, lysosomes, vesicles, endosomes and the cell membrane. The system is defined more accurately as the set of membranes that form a single functional and developmental unit, either being connected directly, or exchanging material through vesicle transport.’

40. Origin of Mitochondria & Chloroplasts
Endosymbiotic theory
Eukaryotic cells take in bacteria as endosymbionts
Aerobic Bacteria become mitochondria
Cyanobacteria become chloroplasts

41. Evidence for Endosymbiotic T
1) Two membrane layers of
A) Outer membrane like host cell
B) Inner membrane like a bacteria

43. 2) Mito. & chloro. have their own DNA
Circular Chromosome
Different genes than nucleus

44. 3) Mito. & Chloro have own ribosomes &
Make own proteins
Ribosomes like bacteria

45. 4) Mito & Chloro grow and reproduce on own