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

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

What They Looked Like

What They Ate

Behavior & Environment 3.6 MYA

Fossils & Ancient Life Fossil Record Fossil Record Organization Of Fossils From Oldest To Newest Including Supporting Information Of Other Life Forms In Their Environment 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 Each Fossil Is Found Only In It’s Particular Time Period or Layer A Kind Of Fossil Clock A Kind Of Fossil Clock Of All The Life Forms That Have Ever Lived On Earth Of All The Life Forms That Have Ever Lived On Earth % Are Extinct 99% Are Extinct No Longer Alive No Longer Alive

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

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

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

Interpreting Fossil Evidence Most Fossils Disarticulated Most Fossils Disarticulated Predation Predation Scavengers Scavengers Rot Rot Catastrophic Events May Bury & Preserve Whole Animals and/or Ecosystems 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 (1 st, 2 nd, 3 rd, 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

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

Relative Dating Index Fossils Index Fossils Easily Recognized Easily Recognized Existed For A Short Period Existed For A Short Period Wide Geographic Distribution Wide Geographic Distribution Does Not Give Absolute Age 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 Patterns of Evolution

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

Macroevolution Key Concept: There Are Six Important Patterns of Macroevolution: 1. Mass Extinctions 2. Adaptive Radiation 3. Convergent Evolution 4. Coevolution 5. Punctuated Equilibrium 6. Developmental Gene Changes

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

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

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

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

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

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

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

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

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

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