Download ENVI 30 Environmental Issues

I.
Origin of Life on Earth
C.
Characteristics of Early Life
1.
Self-Replication
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2.
Proteins aren’t self-replicating
RNA may carry out catalytic functions
Ribozyme – Autocatalytic RNA
RNA may have been first informational molecule
DNA more stable; may have arisen from RNA
Nutrition
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First cells likely heterotrophic
No free oxygen in atmosphere of early earth
First heterotrophs probably used anaerobic fermentation
(less efficient than aerobic metabolism)
First autotrophs may have used hydrogen sulfide (H2S) as
hydrogen source (modern purple & green sulfur bacteria still
get H from H2S)
First autotrophs to split water for H probably ancestors of
modern cyanobacteria (3.1 – 3.5 bya)
Production of O2 had profound effects
I.
Origin of Life on Earth
C.
Characteristics of Early Life
3.
Aerobes
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4.
O2 abundant by 2.5 bya
Replaced obligate anaerobes in most areas
Aerobic metabolism much more efficient than anaerobic
metabolism
Stabilized concentrations of O2 and CO2 in atmosphere
Development of ozone (O3) layer
Eukaryotes
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Appeared ~2.1-2.2 bya
How might eukaryotes have arisen from prokaryotes?
Organelles (mitochondria, chloroplasts) may have originated
from symbiotic relationships between prokaryote species
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Chloroplasts closely related to cyanobacteria
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Mitochondria closely related to alpha proteobacteria
Serial endosymbiosis
Fig. 25.8
I.
Origin of Life on Earth
C.
Characteristics of Early Life
3.
Aerobes
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4.
O2 abundant by 2.5 bya
Replaced obligate anaerobes in most areas
Aerobic metabolism much more efficient than anaerobic
metabolism
Stabilized concentrations of O2 and CO2 in atmosphere
Development of ozone (O3) layer
Eukaryotes
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Appeared ~2.1-2.2 bya
How might eukaryotes have arisen from prokaryotes?
Organelles (mitochondria, chloroplasts) may have originated
from symbiotic relationships between prokaryote species
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Chloroplasts closely related to cyanobacteria
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Mitochondria closely related to alpha proteobacteria
Serial endosymbiosis
Fig. 25.9
Fig. 25.9
Fig. 25.9
I.
Origin of Life on Earth
C.
Characteristics of Early Life
4.
Eukaryotes
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a.
b.
c.
d.
Evidence for serial endosymbiosis
Inner membranes of plastids & mitochondria have
enzymes and transport systems similar to those of
plasma membranes in modern bacteria
Plastids & mitochondria replicate by binary fission
process similar to that of bacteria
Plastids & mitochondria each contain single, circular
DNA molecule without histones or other proteins
(similar to bacteria)
Plastids & mitochondria have ribosomes that resemble
prokaryotic more than cytoplasmic ribosomes (size,
sequence, sensitivity to antibiotics)
II.
Geological Record
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Rocks, sediments, fossils – Occur in
layers (strata)
Oldest fossils – Stromatolites from 3.5
bya
II.
Geological Record
A.
Dating
1.
Index Fossils
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2.
Based on common species
Useful for establishing relative ages
Used by petroleum industry
Radiometric Dating
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Technique for absolute dating
Based on decay of radioactive elements in rocks
Fig. 25.5
II.
Geological Record
A.
Dating
1.
2.
Index Fossils
Radiometric Dating
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Half-life unaffected by temperature, pressure, etc.
Ex: 40K  40Ar with t0.5 = 1.3 billion years
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Initial rock has 100% 40K and no 40Ar
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Rock with 40K:40Ar = 1:1 is 1.3 billion years old
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Rock with 40K:40Ar = 1:3 is 2.6 billion years old
Commonly used radioisotopes
40K with t
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0.5 = 1.3 billion years
235U with t
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0.5 = 704 million years
14C with t
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0.5 = 5730 years
II.
Geological Record
B.
Geological Time Scale
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Earth’s history divided into periods based on
major geological, climatic, & biological changes
Mass Extinction (K-T)
First Bird (150 mya) ?
Mass Extinction (96% of
marine spp.)
First Amniote Egg ?
”Age of Fishes”
First Land Plants/Animals ?
First Fishes
- Siberian Volcanism
- Increased CO2
- Altered Ocean Mixing
Fig. 25.15
Cretaceous Mass Extinction
Fig. 25.16
Time Scale:
One Year
Homo appears:
Dec 31 @ 5 pm
Fig.
25.7
Global Plate Tectonics
Jurassic to Present Day
By
L.A. Lawver, M.F. Coffin, I.W.D. Dalziel
L.M. Gahagan, D.A. Campbell, and R.M. Schmitz
2001, University of Texas Institute for
Geophysics
February 9, 2001
Earth – Future Drift