17-1 the fossil record. fossils remains of once-living things appear in a particular order provide...
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17-1 The fossil record
Fossils
• Remains of once-living things
• Appear in a particular order
• Provide evidence for evolution.
Types of fossils
Leaf imprint
Shell casting
• archaeopteryx
Fossils may be bones or impressions in soft earth that hardened into stone.
Human: 20,000 yrs old Australia
Dinosaur Nat’l Monument, Utah
T Rex footprint
Relative dating
• Fossils are dated by the fossils + rocks around them.
• Gives an estimate of its age.
The Grand Canyon of the Colorado
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Layers contain marine fossils from a shallow sea. Where are the oldest fossils found?
Radioactive dating
• Uses radioactive elements in rock to find absolute age of fossils.
• Carbon-14 used for fossils ‘younger’ than 60,000 yrs.
Geologic time scale
• Precambrian: 88% of Earth’s history: unicellular life
• Paleozoic: invertebrates, vertebrates
• Mesozoic: dinosaurs• Cenozoic: Mammals,
birds
• Clock Model of Earth’s History
Copyright Pearson Prentice Hall
First humans
Firstprokaryotes
Cenozoic Era
Mesozoic Era
Paleozoic Era
Precambrian Time
First land plants
First multicellular organisms
Firsteukaryotes
Radiation of mammals
Accumulation of atmospheric oxygen
Human fossil record
The most complete fossilevidence of a biped primate. 3 million yrs old, stood 3 ft tall
Reconstructed skull
“Lucy”
Facial recreation from fossilremains