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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Fossil Formation

“Lucy”

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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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