EARTHS EVOLUTION THROUGH 22
GEOLOGIC TIME
INTRODUCTION
Earths Evolution Through Geologic Time
CHAPTER OUTLINE
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2.
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3.
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4.
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5.
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6.
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7.
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8.
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Australopithecus
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LEARNING OBJECTIVES/FOCUS ON CONCEPTS
22.2 Outline
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22.4 Explain
22.6 Describe
TEACHING STRATEGIES
Clicker Questions:
Earth Timeline ConceptTest Questions
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History of Earth Quiz Questions
Muddiest Point:
Timing of Earth History Events.
o
Length of Geologic Time / Evidence of Evolution
o
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TEACHER RESOURCES
Web Resources:
Geologic Time
Paleontology
oPaleontological Research Institution
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Dinosaurs
o DinoBuzz: What killed the Dinosaurs?
Specific Fossil Groups
Imagery, Animations, and Videos:
Images
Plate Tectonic Reconstructions
Animations
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Video
ANSWERS TO QUESTIONS IN THE CHAPTER:
CONCEPT CHECKS
22.1 IS EARTH UNIQUE?
2. Earth is the right size to retain an atmosphere of the appropriate size to keep oxygen and
3. The molten core allows for the existence of a magnetic field to protect life from cosmic rays
that would strip away the atmosphere.
22.2 BIRTH OF A PLANET
2. The Big Bang was the cataclysmic event in which an exploding star produced all the elements
in our universe heavier than iron. The Big Bang was a supernova event.
3. The solar nebula was a large, rotating cloud of interstellar dust and gas. As the nebula
contracted, most of its matter collected in the center to form the protosun. The remaining
4. During the Hadean, Earth was mainly covered by a large magma ocean. Within this magma,
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22.3 ORIGIN AND EVOLUTION OF THE ATMOSPHERE AND OCEANS
1. Outgassing is the process through which gasses trapped in the planets interior were released.
2. The most abundant gasses added to Earths early atmosphere through outgassing were
methane, ammonia, carbon dioxide, and water vapor.
3. During photosynthesis, organisms use the Suns energy to produce organic material from
carbon dioxide (CO2) and water (H2O). A by-product of this process is oxygen. Early
4. Early in Earths history, large amounts of sulfur dioxide were present in the atmosphere,
5. Carbon dioxide is readily soluble in seawater, where it often joins other atoms or molecules to
produce various chemical precipitates. The most common compound generated by this
22.4 PRECAMBRIAN HISTORY: THE FORMATION OF EARTHS CONTINENTS
1. The formation of continental crust is a continuation of the gravitational segregation of
Earth materials that began during the final stage of our planets formation when dense
2. Cratons formed through collision and accretion of small crustal fragments into provinces,
and accretion of provinces into large crustal blocks.
4. The supercontinent cycle is the rifting and dispersal of one very large continent
5. When seafloor spreading rates increase, the production of warm oceanic crust is high, and
22.5 GEOLOGIC HISTORY OF THE PHANEROZOIC: THE FORMATION OF EARTHS MODERN CONTINENTS
2. Most Cretaceous age coal is found in western North America due to the widespread formation
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3. Pangaea began to break apart about 185 million years ago.
5. Eastern and western North America were very different from one another during the Cenozoic
because of their relationship to plate boundaries. The eastern portion of North America was
22.6 EARTHS FIRST LIFE
2. Carbonaceous chrondrites are known to contain amino acidlike organic compounds. An
3. Stromatolites are distinctly layered mats composed of the slimy secretions of microscopic
4. Prokaryotes are simple single-celled bacteria that lack nuclei. Eukaryotes are more advanced
22.7 PALEOZOIC ERA: LIFE EXPLODES
2. Cambrian seas were dominated first by cephalopods, and then by fish.
4. Lobe-finned fish were thought to be the first animals to leave the ocean and begin breathing
on land as amphibians.
5. Amphibians are not true land animals because they are not fully adapted to life completely out
6. The development of shell-covered eggs, laid on land, and the formation of evolved lungs,
22.8 MESOZOIC ERA: AGE OF DINOSAURS
1. Gymnosperms, those that produce seeds not enclosed in fruits, became dominant in the
Mesozoic. Modern descendants of these gymnosperms include pines, firs, and junipers.
3. The dominant reptile group on land during the Mesozoic was the dinosaurs.
4. Two reptiles that returned to life in the sea were the fish-eating plesiosaurs and ichthyosaurs.
22.9 CENOZOIC ERA: AGE OF MAMMALS
1. Mammals replaced reptiles as the dominant land animal in the Cenozoic.
2. Prior to this time, mammals were small rodent-like creatures that gathered food at night
4. Humans are separated from other mammals by the presence of a larger brain and longer legs
adapted for upright walking.
EYE ON EARTH
EOE #1 4.4-BILLION–YEAR–OLD ZIRCON
2. The granite in which this zircon first formed was weathered and broken down, and
3. The zircon is older than the metaconglomerate in which it is found. This is because it had
EOE #2 CAMBRIAN STROMATOLITES
1. If these are Cambrian-age, they are 542 to 488 million years old.
3. Modern stromatolites form in warm, shallow oceanic systems, so the environment of this
GIVE IT SOME THOUGHT
1. The Precambrian has fewer divisions than the rest of the time scale because we know much less
2. The Big Bang occurred 13.7 billion years ago, creating hydrogen and helium atoms and formed
our galaxy. Heavy elements synthesized from the supernova explosions, creating a solar nebula
that began contracting about 4.7 billion years ago. The material in the nebula collected and
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3. Iron-rich rocks from the Precambrian suggest that Earths early atmosphere contained much
4. The appearance of oxygen in Earths primitive atmosphere allowed oxygen-dependent life-
5.
a) The most extreme mass extinction was #3 at the end of the Paleozoic.
6. It took several hundred million years for continents to form on Earth and thus rise above sea
level.
7. The eastern portion of North America was tectonically stable (far from a plate boundary),
allowing for abundant marine sedimentation, especially in the Gulf of Mexico. The western
9. Students might agree by describing the chemical and temperature similarities between the two
10.
a) Shallow marine environments would likely diminish in size as the supercontinent formed
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