Download 17-1 The Fossil Record - Mrs. Wahe`s Life Science Class

Chapter 17
The History of Life
Section 17-1
The Fossil Record
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

What They Looked Like
What They Ate
Behavior & Environment
3.6 MYA
Fossils & Ancient Life

Fossil Record

Organization Of Fossils
From Oldest To Newest
Including Supporting
Information Of Other Life
Forms In Their
Environment
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.
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
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
How Fossils Are Formed



Organic Materials Are Replaced By
Minerals
Quality Of Preservation Varies
Fossils Include:




Bones
Eggs
Footprints
Skin Impressions, etc.
Interpreting Fossil Evidence

Fossils Are Released By
Tectonic Forces
 Erosion
 Mining
 Construction

Interpreting Fossil Evidence

Most Fossils Disarticulated
Predation
 Scavengers
 Rot


Catastrophic Events May Bury &
Preserve Whole Animals and/or
Ecosystems
Life On Earth
Dating Fossils
Two Types of Dating
1.
Relative Dating
Organizes Fossils By Order (1st, 2nd, 3rd, etc.)
Tells You Which Organisms Lived In What Order
Does Not Give You Actual Years
2.
Absolute Dating
Gives You Age In Years Before Present
e.g. 150 Million Years Ago
Relative Dating
Relative Dating
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
Relative Dating

Index Fossils
Easily Recognized
 Existed For A Short
Period
 Wide Geographic
Distribution
 Does Not Give Absolute
Age

Relative Dating
Key Concept:
Relative Dating Allows
Paleontologists To Estimate A
Fossils Age Compared With
That Of Other Fossils
Radioactive Dating
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
Radioactive Dating
Key Concept:
In Radioactive Dating, Scientists
Calculate The Age Of A Sample
Based On The Amount Of
Remaining Radioactive Isotopes It
Contains
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
Geologic Time Scale
Developed By Paleontologists To Classify
Geologic And Biologic Events
Rock Layers
Fossils Present
Chapter 17
The History of Life
Section 17- 4
Patterns of Evolution
Macroevolution

Large Scale Evolutionary Changes That
Take Place Over Long Periods of Time
Macroevolution
Key Concept:
There Are Six Important Patterns of
Macroevolution:
1.
2.
3.
4.
5.
6.
Mass Extinctions
Adaptive Radiation
Convergent Evolution
Coevolution
Punctuated Equilibrium
Developmental Gene Changes
Mass Extinctions

Extinction



Occurs Constantly
99% Earths Life Forms Extinct
Mass Extinctions



Wipe Out Ecosystems
Disrupt Energy Flow
Collapse Food Webs
Mass Extinctions

Causes?
Asteroids?
 Volcanic/Geologic Activity?


Effects
Habitats Left Unoccupied
 Ecological Opportunity
 Evolution Explosion

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

Convergent Evolution

Unrelated Species That Look And Act
Remarkably Similar To Each Other But
Are Not Related:
Fish
 Dolphins
 Seals

- Whales
- Sharks
- Penguins
Coevolution

The Process By Which Two Species
Evolve In Response To Changes In
Each Other
Figs & Wasp
 Yucca & Bats
 Orchids & Moths

Punctuated Equilibrium

Evolution Is Sometimes Gradual & Slow
(Gradualism, Darwin)




Horseshoe Crabs
Sharks
Cockroaches
BUT When Ecological Equilibrium Is
Upset, Evolution Can Become Quite “Rapid
Punctuated Equilibrium

Occurs Due To
Small Populations Become
Reproductively Isolated
 Mass Extinctions

Punctuated Equilibrium

Brief Periods of Rapid
Evolutionary Change That
Interrupt Long Periods of Gradual
Evolution

Still Controversial
Developmental Genes & Body Plans
Small Changes In Timing
of Genetic Control
During Embryonic
Development, Make
Big Changes In The
Resulting Organism
Click on the links below

Evolution videos:
http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html

Fossil article:
http://news.bbc.co.uk/2/hi/science/nature/4879672.stm

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Games:
http://www.abc.net.au/beasts/fossilfun/
http://www.ucmp.berkeley.edu/education/expl
orations/tours/fossil/index.html
http://www.abc.net.au/beasts/fossilfun/making
fossils/default.htm