1. Chapter 17 The History of Life
Section 17-1
The Fossil Record

2. Fossils & Ancient Life Paleontologists Scientists Who Study Fossils
Infer What Past Life
Looked Like
What They Ate & What Ate Them
Behavior
Environment They Lived In

3. What They Looked Like

4. What They Ate

5. Behavior & Environment
3.6 MYA

6. Fossils & Ancient Life Fossil Record
Organization Of Fossils From Oldest To Newest Including Supporting Information Of Other Life Forms In Their Environment

7. Fossils & Ancient Life Key Concept
The Fossil Record Provides Evidence About The History Of Life On Earth. It Also Shows How Different Groups of Organisms Have Changed Over Time.

8. Fossils & Ancient Life
Each Fossil Is Found Only In It’s Particular Time Period or Layer
A Kind Of Fossil Clock
Of All The Life Forms That Have Ever Lived On Earth -----
99% Are Extinct
No Longer Alive

9. How Fossils Are Formed Most Form In Sedimentary Rock
Plants & Animals Die In A Water Environment And Are Covered With Silt
Others Covered With Fine Sand or Volcanic Ash
Compressed Into Rock

10. How Fossils Are Formed Organic Materials Are Replaced By Minerals
Quality Of Preservation Varies
Fossils Include:
Bones
Eggs
Footprints
Skin Impressions, etc.

11. Interpreting Fossil Evidence
Fossils Are Released By
Tectonic Forces
Erosion
Mining
Construction

12. Interpreting Fossil Evidence
Most Fossils Disarticulated
Predation
Scavengers
Rot
Catastrophic Events May Bury & Preserve Whole Animals and/or Ecosystems

13. Life On Earth

14. Dating Fossils Two Types of Dating Relative Dating Absolute Dating
Organizes Fossils By Order (1st, 2nd, 3rd, etc.)
Tells You Which Organisms Lived In What Order
Does Not Give You Actual Years
Absolute Dating
Gives You Age In Years Before Present
e.g. 150 Million Years Ago

15. Relative Dating

16. Relative Dating

17. Relative Dating
The Age of a Fossil Is Determined By Comparing Its Placement With Other Fossils In Other Layers Of Sedimentary Rock
Allows Comparison Of Layers World Wide

18. Relative Dating Index Fossils Easily Recognized
Existed For A Short Period
Wide Geographic Distribution
Does Not Give Absolute Age

19. Relative Dating
Key Concept:
Relative Dating Allows Paleontologists To Estimate A Fossils Age Compared With That Of Other Fossils

20. Radioactive Dating Half Life
Uses The Half Lives Of Certain Radioactive Isotopes In Igneous Rocks To Calculate The Age Of A Fossil
Half Life
The Length Of Time Required For Half Of The Radioactive Atoms In A Sample To Decay

21. Radioactive Dating Key Concept:
In Radioactive Dating, Scientists Calculate The Age Of A Sample Based On The Amount Of Remaining Radioactive Isotopes It Contains

22. Different Radioactive Elements Have Different “tick rates”
Radioactive Dating
Different Radioactive Elements Have Different “tick rates”
Carbon-14
Half-life = 5,730 years
Decays to Nitrogen-14
Useful Back 60,000 years

23. Developed By Paleontologists To Classify Geologic And Biologic Events
Geologic Time Scale
Developed By Paleontologists To Classify Geologic And Biologic Events
Rock Layers
Fossils Present

24. Chapter 17 The History of Life
Section Patterns of Evolution

25. Macroevolution
Large Scale Evolutionary Changes That Take Place Over Long Periods of Time

26. Macroevolution Key Concept:
There Are Six Important Patterns of Macroevolution:
Mass Extinctions
Adaptive Radiation
Convergent Evolution
Coevolution
Punctuated Equilibrium
Developmental Gene Changes

27. Mass Extinctions Extinction Mass Extinctions Occurs Constantly
99% Earths Life Forms Extinct
Mass Extinctions
Wipe Out Ecosystems
Disrupt Energy Flow
Collapse Food Webs

28. Mass Extinctions Causes? Effects Asteroids?
Volcanic/Geologic Activity?
Effects
Habitats Left Unoccupied
Ecological Opportunity
Evolution Explosion

29. Adaptive Radiation
Single Species or Small Group of Species Evolve Into Several Different Forms That Live In Different Ways
Darwin’s Finches
Age of Reptiles
Age of Mammals

30. Convergent Evolution Fish - Whales Dolphins - Sharks Seals - Penguins
Unrelated Species That Look And Act Remarkably Similar To Each Other But Are Not Related:
Fish Whales
Dolphins - Sharks
Seals - Penguins

31. Coevolution
The Process By Which Two Species Evolve In Response To Changes In Each Other
Figs & Wasp
Yucca & Bats
Orchids & Moths

32. Punctuated Equilibrium
Evolution Is Sometimes Gradual & Slow (Gradualism, Darwin)
Horseshoe Crabs
Sharks
Cockroaches
BUT When Ecological Equilibrium Is Upset, Evolution Can Become Quite “Rapid

33. Punctuated Equilibrium
Occurs Due To
Small Populations Become Reproductively Isolated
Mass Extinctions

34. Punctuated Equilibrium
Brief Periods of Rapid Evolutionary Change That Interrupt Long Periods of Gradual Evolution
Still Controversial

35. Developmental Genes & Body Plans
Small Changes In Timing of Genetic Control During Embryonic Development, Make Big Changes In The Resulting Organism

36. Click on the links below
Evolution videos:
Fossil article:
Games: