Origin and History of Life
Where it came from and how it
got here
Chapter Outline
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Primitive Earth
Origin of First Cells
Fossils
The Precambrian
The Paleozoic
The Mesozoic
The Cenozoic
Continental Drift
Mass Extinctions
Beginnings
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The Universe (maybe)
Primitive Earth—Not paradise as we know
it—much different than Earth today
Simple to complex
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Question: How could these simple
molecules be made into more complex
ones?
Answer: Abundant energy sources, lots of
time.
Origin of organic molecules
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Alexander Oparin (1938) — a Russian
biochemist with vision
Stanley Miller (1953) – tested the
hypothesis
Miller Apparatus
Other models
 Carbonaceous
 Panspermia
chondrites
Panspermia
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Life brought in on
asteroids and comets
EX. Deinococcus
radiodurans
Abiotic Chemical Evolution
 Synthesis
and accumulation
 Polymerization
 Aggregation
 Origin of heredity
Origin of First Cells
Keep in mind!!!
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Chemical natural selection
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Conditions of primitive earth
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Timescale
Evolution of
Macromolecules
 RNA
first hypothesis
 Protein
 Clay
first hypothesis
hypothesis
RNA first hypothesis
 RNA
contains information like
DNA
 RNA is catalytic-- -- ribozymes.
Protein First Hypothesis
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Most enzymes are proteins
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Proteinoids
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Proteinoid microspheres
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Faithful replication?
Clay hypothesis
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Unique chemical properties of clay.
Combines parts of the RNA first and
protein first ideas.
Protocell Evolves
 Protocells
-- precursors to the first
true cells.
 lipid-protein membrane
 Proteinoid
microspheres
 Coacervates
 Liposomes
Protocell Anatomy
Energy Management
Were the first protocells
heterotrophs or autotrophs?
Origin of First Cells
The Origin of Life 2
Fossils
Fossils are remains and traces of past
life
 Why are they so rare?
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Fossils
Dating Fossils
Relative Dating
Absolute dating
Combination
Strata
The Precambrian Age of microbes
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570 mya - 4.6 bya
The First Cells —3.5-4 billion years ago
What were they like?
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Energy management?
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Aquatic or terrestrial?
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Prokaryote or eukaryote?
Evolution of Autotrophs
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Life as Energy Management
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Chemoautotrophs
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Photoautotrophs
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Atmospheric O2 ~2 BYA
Atmospheric O2—SO WHAT?
O2 is very reactive—Poison.
Cells had to deal with this
Aerobic
Anaerobic
Facultative anaerobes
Changes in atmosphere– O2 and ozone. So?
Consequences for energy acquisition
Circle of Life
Energy
Respiration
Carbon
compounds, O2
CO2, H2O
Photosynthesis
Energy
Eukaryotes evolve
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More complex
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Origin? Endosymbiont hypothesis
nucleoid (DNA)
ribosomes
food granule
prokaryotic
flagellum
plasma membrane
cytoplasm
cell wall
nuclear pore
chromatin (DNA)
nucleus
nucleolus
nuclear envelope
flagellum
rough endoplasmic
reticulum
cytoplasm
intermediate
filaments
plasma
membrane
ribosome
lysosome
microtubules
smooth endoplasmic
reticulum
Golgi
complex
free ribosome
vesicle
mitochondrion
vesicle
1. Anaerobic, predatory
prokaryotic cell engulfs
an aerobic bacterium.
aerobic
bacterium
2. Descendants of engulfed
bacterium evolve into
mitochondria.
3. Mitochondria-containing
cell engulfs a photosynthetic
bacterium.
4. Descendants of photosynthetic
bacterium evolve into chloroplasts.
Multicellularity Evolves
Examples?
Volvox—Simple,
multicellular
Advantages?
Summary of Precambrian
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Earth forms
Prokaryotes evolved
Photosynthesis
Eukaryotes
Multicellularity
Sexual reproduction
Paleozoic
Paleozoic 2
Mass extinction---Disappearance of a
large number of species within a
relatively small time interval.
 opportunities for speciation
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PALEOZOIC- MAJOR EVENTS
What were the major events of the
Paleozoic?
1. three mass extinctions
2. Invertebrates dominated –
exoskeleton
3. Primitive plants invaded land
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PALEOZOIC- MAJOR EVENTS
1.
2.
Vertebrates appeared (jawless
fishes) -- internal skeleton
Insects and amphibians invaded the
land -- -- evolution of flight,
evolution of lungs, evolution of
stronger limbs, strengthened
internal skeleton
PALEOZOIC- MAJOR EVENTS
1.
2.
3.
Reptiles appear
a) Shelled egg
b) Scaly skin
c) Reptiles diversify amphibians
declined
Coal forming forests
Conifers appear
Invasion of Land
 Plants
 Invertebrates
 Vertebrates
Mesozoic
MESOZOIC- MAJOR EVENTS
The age of reptiles
 Angiosperms evolve-insects diversify
 Mammals and birds
 Evolution of endothermy
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QUESTIONS
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From what to did dinosaurs evolve?
From what to do to mammals evolve?
From what did birds evolve?
What caused the mass extinction of
dinosaurs?
Were the dinosaurs endothermic?
Endothermy vs Ectothermy
Endothermy
Warm –blooded
Requires a high use of
energy
High metabolic rate
Disadvantages?
Ectothermy
Cold blooded
Less energy necessary
Regulation?
behavioral
structural
inertial ectothermy
Cretaceous Mass
Extinction
 Bolide
theory -- -- the most
widely accepted theory of the
Cretaceous Mass extinction.
 Bolide -- -- and exploding
asteroid.
Cenozoic
CENOZOIC- MAJOR EVENTS
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Three mass extinctions
Decline of reptiles
Diversification of
 Angiosperms
 Insects
 Birds
 Mammals
Factors That Influence Evolution
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Continental Drift
 Positions of continents and oceans are
not fixed.
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How does this explain the presence of
marsupials and monotremes in
Australia?
Continental Drift
Continental Drift
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Plate Tectonics
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Movements of Earth’s crust which is
fragmented into slablike plates that float on a
lower hot mantle layer.
Plate Tectonics
Mass extinctions
A mass extinction occurs when a large fraction
of all living species becomes rapidly extinct.
The fossil record shows that at least five major
mass extinctions have occurred in the past 500
million years.
Impacts of asteroids on Earth are suspected as a
primary cause of mass extinction.
Mass Extinctions
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Mass extinctions have occurred throughout
history. At the ends of:
 Ordovician
 Continental Drift
 Devonian
 Bolide Event
 Loss of 70% of marine invertebrates
Mass Extinctions
Permian
 Excess carbon dioxide.
 Loss of 90% of ocean species.
 Triassic
 Meteorite Collision
 Cretaceous—probably a bolide.
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Permian Mass Extinction
At the end of the Permian period (about 245
mya), destroyed 90-95% of marine and
70% of land species.
Possibilities?
 The glaciation of Gondwanaland
 the increased fluctuation of global
temperatures
 volcanic eruptions occurring in Siberia
Mass Extinctions
Intrinsic gradualism
Extinction caused
primarily by climate
change or other
gradual processes.
EX. Global warming
Extrinsic catastrophism
Extinction caused by a
catastrophe
Ex. Asteroid collision
with Earth
Review
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Primitive Earth
Origin of First Cells
Fossils
The Precambrian
The Paleozoic
The Mesozoic
The Cenozoic
Continental Drift
Mass Extinctions