HONP210 Lecture Topics 11105

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HONP210 Lecture Topics 11/1/05

• Origin and Evolution of Early Life
• Cambrian Explosion, K-T Boundary, Humans

Read Chapter 5 Field trip on Saturday, 11/5 -
meet at 745am at the NJ Transit bus stop near
College Hall
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Important Events in Earth History
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Important Dates in History of Life on Earth
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History of Life on Earth
Prokaryotes
Eukaryotes
Protists
Bacteria
Archaea
Plants
Fungi
Animals
Cenozoic
First humans
Mesozoic
Extinction of dinosaurs
Plants and symbiotic fungi colonize land
Paleozoic
Oldest animal fossils
Origin of multicellular organisms
Oldest eukaryotic fossils
Accumulation of atmospheric oxygen from
photosynthetic cyanobacteria
Precam-brian
Oldest prokaryotic fossils
Earth cool enough for crust to solidify
Origin of Earth
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When Did Life Begin?
Somewhere between 4.0 and 3.5 Ga

• Three lines of fossil evidence
• Stromatolites
• Fossilized cells
• Geochemical evidence

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v
Stromatolites finely laminated structures in
limestones
Oldest are 3.2 to 3.5 Ga
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Modern Stromatolites (W. Australia)
Mats of photosynthetic blue-green algae
mixed with layers of sediment
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Microfossils (?) interpreted as fossilized
cells in 3.2 to 3.5 Ga rocks from at least three
separate localities on Earth.
3.5 Ga fossilized bacteria?
modern bacteria
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Geochemical Evidence
Distinctive 13C/12C in 3.85 Ga metasedimentary
rocks from SW Greenland suggest biological
activity.
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Where did life begin?
Not likely, no ozone to protect from UV radiation
heavy bombardment
1. Land surface?
Not likely, not enough chemical energy heavy
bombardment
2. Shallow ponds?
3. Deep sea vents (black-smokers) or hot springs
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DNA evidence suggests that organism closest to
the branching point of the common ancestor
where EXTREMOPHILES
Adapted to life in hot water (100-400C) and use
chemical energy instead of photosynthesis
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Inorganic compounds
How did life begin?
Abiotic synthesis (Organic Soup)
Simple organics
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Polymerization Self-replication (RNA World)
Complex organics

• Three-Stage Hypothesis for the Origin of Life

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RNA
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Packaging in Pre-Cell
Membrane-enclosed compartment
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Step 1 Synthesis of Simple Organic Molecules
(Production of the Organic Soup)
Miller-Urey Experiment
Lab experiments have synthesized all the basic
organic molecules necessary for life, in
particularly bases used in RNA and DNA
Chemical reactions probably took place in the
atmosphere, or near black-smokers and hot
springs. Also could have been brought in from
meteorites and comets

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Step 2 Synthesis of Complex Organic Molecules
(Production of an RNA World)
Clay minerals may have served as a template
RNA begins to self-replicate
Complementary chain serves as template for
making copy of original gene
Formation of short RNA polymers RNA World
Assembly of a complementary RNA chain
RNA monomers Organic Soup"
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Step 3 Molecular Organization into a Pre-Cell

• Some RNA are trapped in a pre-cell membrane.
  This is advantageous.
• speeds molecular reactions
• facilitates natural selection

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• Laboratory experiments demonstrate that pre-cells
  could have formed spontaneously from abiotically
  produced organic compounds

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Summary of Hypothesis for the Origin of Life
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Early Microbial Evolution
Rapid mutation rates led to many different types
of metabolism
Simple, anaerobic, most were probably
chemoautotrophs
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History of Life on Earth
Prokaryotes
Eukaryotes
Protists
Bacteria
Archaea
Plants
Fungi
Animals
Cenozoic
First humans
Mesozoic
Extinction of dinosaurs
Plants and symbiotic fungi colonize land
Paleozoic
Oldest animal fossils
Origin of multicellular organisms
Oldest eukaryotic fossils
Accumulation of atmospheric oxygen from
photosynthetic cyanobacteria
Precam-brian
2.5 Ga
Oldest prokaryotic fossils
Earth cool enough for crust to solidify
Origin of Earth
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Oxygen in Atmosphere Through Time
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Banded Iron Formations
rusting of the Earth at 2.5 to 2.0 Ga
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History of Life on Earth
Prokaryotes
Eukaryotes
Protists
Bacteria
Archaea
Plants
Fungi
Animals
Cenozoic
First humans
Mesozoic
Extinction of dinosaurs
Plants and symbiotic fungi colonize land
Paleozoic
Oldest animal fossils
Origin of multicellular organisms
Oldest eukaryotic fossils
2 Ga
Accumulation of atmospheric oxygen from
photosynthetic cyanobacteria
Precam-brian
Oldest prokaryotic fossils
Earth cool enough for crust to solidify
Origin of Earth
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Eukaryotic Cell Evolution
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History of Life on Earth
Prokaryotes
Eukaryotes
Protists
Bacteria
Archaea
Plants
Fungi
Animals
Cenozoic
First humans
Mesozoic
Extinction of dinosaurs
Plants and symbiotic fungi colonize land
Paleozoic
Oldest animal fossils
Origin of multicellular organisms
1 Ga
Oldest eukaryotic fossils
Accumulation of atmospheric oxygen from
photosynthetic cyanobacteria
Precam-brian
Oldest prokaryotic fossils
Earth cool enough for crust to solidify
Origin of Earth
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HONP210 Lecture Topics 11/1/05

• Origin and Evolution of Early Life
• Cambrian Explosion, K-T Boundary, Humans

Read Chapter 5 Field trip on Saturday, 11/5 -
meet at 745am at the NJ Transit bus stop near
College Hall
27
History of Life on Earth
Prokaryotes
Eukaryotes
Protists
Bacteria
Archaea
Plants
Fungi
Animals
Cenozoic
First humans
Mesozoic
Extinction of dinosaurs
Plants and symbiotic fungi colonize land
Paleozoic
Oldest animal fossils
600 Ma
Origin of multicellular organisms
Oldest eukaryotic fossils
Accumulation of atmospheric oxygen from
photosynthetic cyanobacteria
Precam-brian
Oldest prokaryotic fossils
Earth cool enough for crust to solidify
Origin of Earth
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The Cambrian Explosion
All 30 different phyla in the animal kingdom
appeared within 40 million years (lt1 of geologic
time) at 545 Ma.
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Trilobite
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Cambrian Animal Community
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The Cambrian Explosion

• Possible Reasons
• Atmospheric O2 reached critical level (50 of
  todays level).
• Genetic complexity reached a critical level for
  rapid evolution.
• Climate change - Earth just came out of severe
  cold period (Snowball Earth).
• No predators.

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History of Life on Earth
Prokaryotes
Eukaryotes
Protists
Bacteria
Archaea
Plants
Fungi
Animals
Cenozoic
First humans
475-360 Ma
Mesozoic
Extinction of dinosaurs
Plants and symbiotic fungi colonize land
Paleozoic
Oldest animal fossils
Origin of multicellular organisms
Oldest eukaryotic fossils
Accumulation of atmospheric oxygen from
photosynthetic cyanobacteria
Precam-brian
Oldest prokaryotic fossils
Earth cool enough for crust to solidify
Origin of Earth
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The Colonization of Land
475 Ma - Plants
400 Ma - Animals
Carboniferous Forest (360 Ma)
Development Ozone Layer (O3) ??
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Important Events in Earth History
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Impacts and Mass Extinctions on Earth
We know that larger objects have impacted Earth

• Meteor Crater in northern Arizona
• caused by a 50-meter asteroid
• impact occurred 50,000 years ago

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Impacts and Mass Extinctions on Earth

• 65 million years ago, many species, including
  dinosaurs, disappeared from earth
• Sedimentary rock layer from that time shows
• Iridium, Osmium, Platinum
• grains of shocked quartz
• spherical rock droplets
• soot from forest fires

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K-T Boundary Layer (65 Ma)
Sediment layer rich in Ir (Iridium).
Tertiary Rocks
Cretaceous Rocks
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• In 1991, a 65 million year old impact crater was
  found on the coast of Mexico.
• 200 km in diameter implies an asteroid size of
  about 10 km across

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• debris in atmosphere blocks sunlight plant
  dieanimals starve
• poisonous gases form in atmosphere

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Mass Extinctions on Earth
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Mass Extinctions on Earth

• Other Possible Causes
• Unusually Active Volcanism
• Climate Change
• Thinning of Ozone Layer
• Magnetic Reversals
• Nearby Supernova

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Where do we come from?
Common ancestor 5- 8 Ma
Primate Evolutionary Tree
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Hominid Evolution
Oldest Homo sapien fossil skulls are 100,000
years old
Common Ancestor (?, 5 Ma)
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Important Events in Earth History