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Bio Ch17 – History of Life on Earth
How long has life been on Earth?
What are the relationships between organisms as time moved forward?
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Fossil Records
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Fossil Records
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Petrified tree sap = “amber”(Basis for Jurassic Park movies)
Fossil Evidence
In 2004, scientists digging in the Canadian Arctic unearthed fossils of a half-fish, half-
amphibian that all but confirmed paleontologists' theories about how land-dwelling tetrapods–four-limbed animals,
including us–evolved from fish. It is a classic example of a transitional form,
one that bridges a so-called evolutionary gap between different types of animal. Let’s examine five important cases.
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Age-determining Techniques
• Biological – tree rings• Geologic – sedimentary layers• Geochemical – Sea salt concentration• Geophysical – Relative cooling of earth’s crust• Chemical – Weathering• Relative dating – Fossil relations• Radioactive dating – Comparative amount of
elements
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Relative Dating
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Radioactive dating
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Radioactive decay
in everyday life
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Geologic Time Scale
Evidence used to construct “timeline” of development of life on Earth
• Fossil records• Relative Dating• Radioactive dating
LEADS TO
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Early Earth Atmosphere
•Hydrogen Cyanide
•Carbon Dioxide
•Carbon Monoxide
•Nitrogen
•Hydrogen Sulfide
•Water
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Patterns of Evolution (Macroevolution)
• Extinction
• Adaptive Radiation
• Convergent Evolution
• Coevolution
• Punctuated Equilibrium
• Changes in developmental genes
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Extinction
• Mass extinctions– Causes– Impact on life
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Adaptive Radiation
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Convergent Evolution
Similar torpedo-shape body & fluke/tail.
Mammals were initially land-based with four walking limbs.
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Coevolution
• Evolution of separate species in response to each other (not abiotic response)
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Punctuated Equilibrium
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Changes in Developmental Genes
• Genetic change can produce major evolutionary transformation
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