1. Origin of Life

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

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

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

5. III. Macromolecules chains of molecules proteins carbohydrates lipids
nucleic acids

6. IV. Requirements for macromolecules to form on their own
A. energy source:
1. lightning 2. geothermal vents
B. concentration: to bring materials together
1. tide pools/evaporation
2. clay

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

8. V. Cell membrane formation
each phospholipid has a hydrophobic end and a hydrophilic end
when surrounded by water, phospholipids form a sphere
hydrophobic ends protected on the inside

9. Protobionts fatty acid spheres that form naturally
Macromolecules & enzymes inside
reactions occur inside
Grow
divide
selectively absorb &
release compounds
digest starch
store & release energy

10. 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

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

12. VI. Nucleic acid reproduction
RNA can assemble on its own
Can replicate (make more copies)
Can pass on genetic info when cell divides

13. VII. Earliest Life Forms 3.5 bya
3.4 byo, South Africa
1) prokaryotic bacteria
2) anaerobic: live without O2
4) heterotrophs
3) fermenters:
use organic molecules for energy
modern

14. VIII. The First Energy Crunch
organic molecules become scarce
competitive advantage goes to –
organisms that can make their own food
photosynthesis

15. Photosynthesis
light-absorbing pigments (like chlorophyll) already present
chlorophyll form spontaneously

16. First Cyanobacteria 3.5 bya
O2 released as a by-product
problem: O2 breaks bonds of organic molecules
(i.e. - it’s toxic)
6CO H2O
carbon
dioxide
water
C6H12O O2
sugar
oxygen
energy from sunlight

17. Living
Precambrian
Cyanobacteria
Ancient vs. Modern

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

19. 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?

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

21. 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

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

23. Aerobic Bacteria some bacteria evolved antioxidants
allowed those bacteria to survive rising O2 levels by 1.8 bya
some bacteria even evolved to use O2…
By doing aerobic respiration

24. Origin of Nucleus & E. R.

25. Nucleus formation = First Eukaryotes
Mid-Proterozoic Eon
Fossils 1.5 – 2 bya

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

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

29. Evidence for Endosymbiotic T
2) Mito. & chloro. have their own DNA
Circular Chromosome like bacteria
Different genes than are in the host nucleus

30. Evidence for Endosymbiotic T
3) Mito. & Chloro have own ribosomes &
Make their own proteins different from host
Ribosomes like bacteria

31. Evidence for Endosymbiotic T
4) Mito & Chloro grow and reproduce on own