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Objective: Examine evidence to support the age of the
Earth and the history of life.
1. Chapter 17
◦ Study your notes every day
◦ Stop in for extra help if you need it before tests
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2. Chapter 15 and 16 Tests
◦ All Grades in Genesis
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3. Review and Homework
Chapter 17
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Paleontologists study fossils.
Fossil Record provides evidence of the history life on Earth.
◦ Infer structure of organisms
◦ What they ate
◦ Environments they lived in
Fossils appear in a particular order.
◦ Some only present in older rocks
◦ Some only in newer rocks
Recall that fossils form in sedimentary rock.
 Weather breaks down rock into small particles.
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◦ Particles carried by water where they settle to the bottom.
◦ Pressure and chemical processes preserve remains into
rock.
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Why is the fossil record an incomplete record of life on
Earth?
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Identify and compare anatomical structures between fossils
and living organisms.
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Age of a fossil is determine by two techniques.
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1. Relative Dating
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2. Radioactive Dating
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Determines age of fossil by comparing its placement with other
fossils in various layers of rock.
◦ Oldest layers on bottom
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Index fossils are easily recognizable for comparison.
◦ Existed for a short period of time
◦ Wide geographic range
◦ Found in specific layers of rock in different locations.
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Use of radioactive decay to assign ages to fossils.
◦ Some elements are radioactive
◦ Decay is measured as HALF-LIFE or the time for half of the
radioactive atoms in a sample to decay
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Age of a fossil based upon amount of remaining radioactive
isotope it contains.
Different radioactive elements have different half-lives.
Carbon 12  most common and does not decay
Carbon 14  radioactive and decays into N-14
◦ Has half-life of 5730 Years
◦ More C-12 compared to C-14 = older fossil
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Which of the following cannot be determined through fossils?
A. the approximate age of the organism
B. other organisms closely related to the fossilized organism
C. anatomical structure of an organism
D. physiological processes of the organism
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Objectives: Investigate factors that led to the formation of
Earth and early forms of life.
1.
2.
3.
4.
5.
Question of the Day
Continue Chapter 17 Notes
Complete the Guided Reading Packet
Chapter 16 Tests
Review and Homework
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Represents evolutionary time.
Precambrian Time 
 Eras 
 Periods
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Cenozoic – Age of
Mammals
65 mya to present
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Precambrian Time
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Paleozoic, Mesozoic, and Cenozoic Eras
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Eras are further subdivided into Periods
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Periods range from 10s of millions of years to 2 million years
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Birth of planet took place over 100 million years
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Collisions with other large objects
◦ Produced tremendous amount of heat
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Most dense elements formed Earth’s core
◦ Decay created a molten rock core
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Moderately dense elements cooled into Earth’s crust.
Least dense formed first atmosphere
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NOTES are in the Guided Reading Packet.
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Answer Key is posted on my webpage.
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Miller and Urey’s Experiment – 1950s
Atoms do not assemble themselves into complex molecules
or living cells today.
◦ Oxygen is very reactive
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See FIGURE 17-8 PAGE 424
Suggested how mixtures of organic compounds necessary for
life could have been formed from simpler compounds
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Radioactive Uranium-232 has a half-life of approximately 70
years. The Chernobyl Nuclear Power Plant Disaster in 1986
released high levels of radiation into nearby surrounding
areas including the town of Pripyat.
What year would see a reduction in radiation to 20% of the
original level of uranium-232?
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Briefly describe how Miller and Urey simulated Earth’s early
atmosphere.
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Mixed hydrogen, methane, and ammonia with water vapor.
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Charged the mixture with electric sparks.
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Cooled the mixture of gases.
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Found the formation of amino acids and other organic
compounds.
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Objectives: Investigate factors that led to the formation of
Earth and early forms of life.
1. Question of the Day
2. Complete the Guided Reading Packet
3. Discuss 17-2 Guided Reading Questions
◦ Packet DUE TOMORROW – THURSDAY March 27
◦ Answer Key will be posted on my webpage
◦ Any late work will receive a 50% penalty.
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4. Review and Homework
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What event was necessary for the first cells to appear on the
planet?
What types of organisms did these first cells resemble?
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Which of the following statements is true?
A. Anaerobic organisms require oxygen to survive.
B. Aerobic organisms can survive in environments with or
without oxygen.
C. Aerobic organisms do not require oxygen for cellular
processes.
D. Anaerobic organisms will die in an oxygen-rich
environment.
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What are the three pieces of evidence that support the
Endosymbiotic Theory?
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1. Mitos and Chloros contain DNA similar to bacterial DNA.
2. Have ribosomes whose size and structure closely resemble
those found in bacteria.
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3. Reproduce by binary fission like bacteria.
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How do cells reproduce?
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Objectives: Investigate factors that led to the formation of
Earth and early forms of life.
1. Question of the Day and DO NOW
2. 17-2 Homework Check
3. 17-3 Evolution of Multicellular Life
◦ Answer Key will be posted on my webpage TOMORROW
◦ Any late work will receive a 50% penalty.
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4. Review and Homework
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http://www.bing.com/videos/search?q=Miller+and+Urey+Ex
periment+Animation&Form=VQFRVP#view=detail&mid=CDF2
71175991A1838660CDF271175991A1838660
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Precambrian Time- 90% of Earth’s history
◦ Life only existed in the seas
◦ Simple anaerobic life  photosynthetic forms  aerobic
life
◦ Eukaryotes  Multicellular organisms
◦ Why do very few fossils exist from this time?
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Cambrian Period – Cambrian Explosion
◦ Invertebrates, brachiopods, arthropods (trilobites)
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Devonian Period – Plants adapt to drier areas
◦ Insects
◦ Age of Fishes – jaws, bony skeletons, scaled bodies
SHARKS!!!
First land animals – amphibians
Carboniferous Period – reptiles and giant insects
plant remains  coal
Mass Extinction – 95% of life extinct
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Dominance of dinosaurs and flowering plants
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Triassic Period – Age of Reptiles
◦ 225 mya  first dinosaurs
◦ First mammals very small
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Jurassic Period – Dinosaurs ruled Earth
◦ Archaeopteryx appeared – first birds
◦ Fossils show skulls/teeth of dinos but body and feathers of birds
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Cretaceous Period – T. rex and flying reptiles
◦ Flowering plants produced seeds enclosed in fruit
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EXTINCTION EVENT
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Age of Mammals
Mammals evolve to live in different environments
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Tertiary Period – Earth warm and mild
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◦ Whales and dolphins evolve
◦ Grasses provide food source for grazing mammals
Quaternary Period – Ice Ages
Ocean levels drop 100 meters
20,000 years ago – climate warms
Mammals such as bats, cattle, mammoths common
200,000 years ago – first fossils of Homo sapiens in Africa
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What is macroevolution?
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1. Extinction
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Most researchers look for a single massive event – Asteroid
striking Earth at Chicxulub Crater, Mexico
◦ Extinction of dinosaurs
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Ecosystems collapse due to natural factors (earthquakes,
volcanoes)
◦ Organisms still able to compete
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Food webs destroyed
Disrupts energy flow
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adaptive radiation: multiple species evolve from a
single species
◦ also known as divergent evolution
◦ Darwin’s Finches
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convergent evolution: different species evolve to have
similar appearances and behaviors
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Different groups of mammals or dinosaurs
Different locations
Different times
Similar environments
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Process in which two species evolve in response to changes in
each other over time
◦ An evolutionary change in one organism 
◦ A corresponding change in another organism
◦ Plant defense vs. fedding insect
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punctuated equilibrium:
involves long periods of
stability that are interrupted
by episodes of rapid change
gradualism: evolution occurs
slow and steady over a long
period of time
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Recall the function of HOX Genes.
Changes in genes can produce changes in growth and
differentiation during embryonic stages of life.
◦ Turning genes OFF
◦ Changing timing of cell differentiation and gene expression
◦ Long vs short legs
◦ Single winged vs double winged
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punctuated equilibrium:
involves long periods of
stability that are
interrupted by episodes of
rapid change
gradualism: evolution
occurs slow and steady
over a long period of time