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Chapter 17: The History of Life
Fossils & DatingFossils are preserved remains of ancient organisms. The Fossil Record provides paleontologists with a way to discern exactly how old the preserved remains are.
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Scientists useRadioactive and Relative
Dating to determine fossil age.
Ziyad Abdelfattah
Geological Time Scale QuickTime™ and aTIFF (Uncompressed) decompressor
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The geologic time scale represents the eras and periods since Precambrian Time, which was about 650 million years ago.
Currently it is the Cenozoic Era (“the age of mammals”), which is represented by a very small portion of the entire geologic time scale.
Joseph Ernst
Formation of the EarthThe formation of the Earth occurred over about 100 million years. Elements were arranged according to density and the least dense elements formed the early atmosphere.
The early atmosphere was made up of hydrogen cyanide, carbon dioxide, carbon monoxide, nitrogen, hydrogen sulfide, and water.
Ziyad Abdelfattah
Early LifeThe organic compounds needed for life derived from compounds that were in Earth’s atmosphere billions of years ago.
Billions of years ago, photosynthetic bacteria in the ocean were busy producing oxygen. This rise of oxygen made some life forms become extinct and made other life forms evolve.
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Joseph Ernst
Summary of Eras and Periods• Precambrian time: Almost 90% of
Earth’s history.• Paleozoic Era: During this era,
marine life flourished, animals began to invade the land, and reptiles evolved.
• Mesozoic Era: The Mesozoic Era was dominated by dinosaurs, who occupied most niches.
• Cenozoic Era: The Cenozoic Era allowed mammals to occupy the niches left empty by the now-extinct dinosaurs.
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Patterns of MacroevolutionMacroevolution is important evolutionary changes that occur over long periods of time
Examples of these macroevolutionary patterns include: mass extinctions, adaptive radiation, convergent evolution, coevolution, punctuated equilibrium, and changes in developmental genes.
Joseph Ernst
Review• The Fossil Record provides evidence of
ancient life on Earth.• The first organic compounds arose from
materials present on primitive Earth.• After Precambrian Time, organisms flourished
in water, invaded the land, and after the extinction of dinosaurs, mammals filled the available niches.
• Macroevolution is evolutionary changes that occur over long periods of time.
Ziyad Abdelfattah
Credits
• Us• Our knowledge• Our expertise• Our skillz• Google Images• “Prentice Hall Biology,” by Miller &
Levine, Copyright 2002, Pearson Education
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Joseph Ernst Ziyad Abdelfattah
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