The Fossil Record

1. The Fossil Record Chapter 5

2. objectives • SPI 0807.5.5 Compare fossils found in sedimentary rock to determine their relative age. I can: • Compare fossils found in sedimentary rock to determine their relative age. • Identify types of fossils. • Explain how fossils are used to interpret the past. • Explain the geologic time scale.

3. Geologic History • Uniformitarianism: geologic change happen through slow gradual processes. • Most geologic change • Catastrophism: geologic change occurs suddenly by catastrophes. • Asteroid, comets, earthquakes, volcanoes I can explain how fossils are used to interpret the past.

4. Relative age (#77) • Examines the position within rock layers to estimate the age of an object. • Look for key words such as before, after, older, younger • Examples: • Before the dinosaurs existed • Older than my brother • After the extinction of the dinosaurs • Bottom layers: oldest • Top layers: youngest I can compare fossils found in sedimentary rock to determine their relative age.

5. Absolute age • Precisely measures the age of fossils or rocks in years. • Examples: • 5780 years ago • Born in 1900 • At the beginning of the Triassic period I can compare fossils found in sedimentary rock to determine their relative age.

6. Types of Fossils • Fossil (#36): Remains or physical evidence of an organism preserved by geologic processes. • Fossils in rock: formed when organism dies and quickly covered by sediment. • Hard parts of the organism are preserved • Soft parts decay I can identify types of fossils.

7. Types of fossils • Fossils in amber: entire organisms preserved inside hardened tree sap. • Insect gets caught in sticky sap, and then hardens. • Some of the best fossils. I can identify types of fossils.

8. Types of fossils • Petrification: minerals replace the organism’s tissues. I can identify types of fossils.

9. Types of fossils • Fossils in asphalt • Thick, sticky pools trap and preserve organisms. • The La Brea asphalt deposits in Los Angeles, California have preserved organisms for at least 38,000 years. I can identify types of fossils.

10. Types of fossils • Frozen Fossils • In 1999, scientists removed a 20,000-year-old woolly mammoth that was frozen in the Siberian tundra. • These mammoths became extinct about 10,000 years ago. • Because cold temperatures slow down decay, the mammoth was almost perfectly preserved. I can identify types of fossils.

11. Types of trace fossils Trace fossils: naturally preserved evidence of animal activity. • Tracks • Reveal size and speed of an animal. • Burrows • Preserved shelters. • Coprolite • Preserved animal dung. I can identify types of fossils.

12. Types of trace fossils • Molds: a cavity in rock where an organism was buried • Sunk in/hole • Cast: created when sediment fills a mold and becomes rock. • Raised up I can identify types of fossils.

13. Index fossils • Index fossils (#44): fossils of organisms that lived for a relatively short, well-defined geologic time span. • Ammonites • Marine mollusks similar to modern squid. • Lived b/t 230 million and 208 million years ago I can identify types of fossils.

14. Index fossils • Trilobites • Closest living relative is the horseshoe crab • Lived about 400 million years ago • When scientists find fossils of trilobites anywhere on Earth, they assume the rock layers are also approximately 400 million years old I can identify types of fossils.

15. Using fossils to interpret the past • Gives a rough sketch of the history of life on Earth. • Organisms with hard body parts have left more fossils. • Organisms that lived in areas that favored fossilization have left more fossils. I can explain how fossils are used to interpret the past.

16. Using fossils to interpret the past • Show a history of environmental change. • Marine fossils found on mountaintops in Canada means that these mountains formed at the bottom of the ocean. • Detect the presence of ancient seas • Reconstruct ancient coastlines • Reconstruct past climates • Determine relationships and similarities between fossils I can explain how fossils are used to interpret the past.

17. Geologic time • Earth is about 4.6 billion years old. • The Grand Canyon • Colorado River has cut/eroded away nearly 2 km deep in some places. • Represent almost half, nearly 2 billion years, of Earth’s history. I can explain the geologic time scale.

18. Geologic time scale • Geologists divided Earth’s history into a scale with distinct sections of time. • Eons: largest division of geologic time • Four eons: Hadean, Archean, Proterozoic, Phanerozoic • Eras: 2nd largest division of geologic time • Periods: 3rd largest division of geologic time • Epochs: 4th largest division of geologic time I can explain the geologic time scale.

19. I can explain the geologic time scale.

20. Phanerozoic era • Paleozoic Era (Old Life) • Marine life flourished, few land animals • Land plants appeared • By the end of the era, amphibians and reptiles lived on the land. • Ended with the largest mass extinction(#33) in history • 90% of all species became extinct I can explain the geologic time scale.

21. Mesozoic era • Mesozoic Era (Age of Reptiles) • Dinosaurs dominated the land • Small mammals • Birds • Ended with a mass extinction • 15-20% of all species became extinct • Possibly caused by global climate change I can explain the geologic time scale.

22. Cenozoic era • Cenozoic era (Age of Mammals) • Mammals flourished • Adaptations may have helped them survive the extinction of the dinosaurs caused by environmental changes. • Regulate internal body temperature • Develop young inside the mother I can explain the geologic time scale.