1. The History of Life
Ch. 17

2. Fossils and Ancient Life
Paleontologist are scientists who study fossils.
Fossil Record provides evidence about the history of life on Earth . It also shows how different groups of organisms, including species, have changed over time.
More than 99% of all species that have ever lived on Earth have become extinct.

3. How Fossils Form Most fossils form in sedimentary rock.
Sedimentary rock is formed from small particles of sand, silt, and clay.
Soft parts of organisms are typically not preserved but hard parts like bones or wood are.

4. Things that can form fossils
Eggs
Footprints
Body Parts

5. Fossil Evidence
Relative dating – use of Carbon Dating can provide a relative age for a fossil.
Relative dating allows paleontologist to estimate a fossil’s age compared with that of other fossils.
Index Fossils – organisms that must have existed for a short period over a wide geographic range.
Half-Life – length of time required for half of the radioactive atoms in a sample to decay

6. Geologic Time Scale
The basic divisions of time from larger to smaller is eras and periods.

7. Eras Precambrian – Characterized by small multicellular life forms
Paleozoic – diversity of marine life
Meozoic – marked by appearance of flowering plant life
Cenozoic – mammals become predominant life forms. Most recent Era

8. Paleozoic Era Major Point:
Cambrian Explosion – the massive diversification of life during the early Cambrian Period
Major Mass Extinction:
The mass extinction at the end of the Paleozoic Era affected both plants and animals on land and in the seas. As much as 95% of the complex life in the oceans disappeared.
Ex. Trilobites and many amphibians became extinct.

9. Mesozoic Era
Major Characteristic: This is when dinosaurs became the predominate life forms and when flowering plants appeared.

10. MacroEvolution

11. Macroevolution Extinction Adaptive radiation Convergent evolution
Coevolution
Punctuated equilibrium
Changes in developmental genes

12. Extinction
Mass extinctions made rapid evolution of surviving species possible because it made new habitats available to them.

13. Adaptive Radiation One common ancestor.
Different environmental stressors (needs) encourage the success of organisms with specific traits.

14. Convergent Evolution Different ancestors SAME environmental stressors.
Causes different species to have similar physical traits.

15. Coevolution
Two species that interact closely together change over time so that both species benefit the most.

16. Punctuated Equilibrium
Common ancestor but sudden changes in each organism.

17. Changes in Developmental Genes
Over time, changes in genes cause organisms to look much different than their ancestors.

18. Punctuated Equilibrium
Convergent Evolution
Coevolution
Adaptive Radiation