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Questions and Answers
Which of the following is most closely associated with the diversification of life forms, including invertebrates and the first land plants?
What major event is characterized by a rapid increase in the diversity of marine life and the emergence of many major animal groups?
The Proterozoic Eon is known as the age of what?
Which of the following eons is currently ongoing?
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What geological event marks the end of the Paleozoic Era?
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Which of these organisms evolved during the Archean Eon?
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The Phanerozoic Eon is divided into three eras. Which of the following is NOT one of these eras?
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Which life form is attributed to being one of the first oxygen-dependent animals during the Proterozoic Eon?
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What significant change occurred due to the collision of continents during the formation of Pangaea?
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During which period did the first vertebrate herbivores appear on land?
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What is the most significant extinction event known for the disappearance of nearly 90% of species?
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During which era did dinosaurs dominate the Earth?
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Which group of plants first appeared during the Jurassic Period?
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What major geographical change began in the early Jurassic period?
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What notable event is associated with the beginning of the Cenozoic Era?
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Which major extinction event occurred at the end of the Permian Period?
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What significant event is known as the Cambrian Explosion?
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Which landmass was formed by the collision of Laurentia and Gondwana during the Paleozoic Era?
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During which period did jawed fish, such as Placoderm, first appear?
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What type of organisms dominated the marine life during the Devonian period?
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What major event marked the end of the Ordovician period?
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Which of the following is not a characteristic of the Carboniferous period?
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Which type of land plants first appeared during the Ordovician period?
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What was the dominant form of marine life during the Cambrian period?
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Study Notes
Geological Time Scale
- A chronology of Earth's history based on geological records and life forms
- Organized into eons, eras, periods, and epochs
Eons
- Largest division of the geological time scale
- Two divisions, Precambrian and Phanerozoic
Precambrian Eon
- Earliest portion of Earth's history
- Three subdivisions: Hadean, Archean, Proterozoic
Hadean Eon
- 4.6 – 4 billion years ago
- The solar system formed within a cloud of dust and gas
- Earth cooled and solidified from molten lava to a solid crust
- Oceans formed
Archean Eon
- 4 – 2.5 billion years ago
- The first life forms evolved in the oceans
- Cyanobacteria evolved during this eon
- Cyanobacteria were the first photosynthetic organisms, using water and sunlight for energy, releasing oxygen as a byproduct
Proterozoic Eon
- "Age of Hidden Life"
- Started 2.5 billion years ago
- Shield rock formed, allowing recognizable geological processes like plate tectonics
- Fossil remains of bacteria and blue-green algae
Phanerozoic Eon
- Covers 541 million years to the present.
- Subdivided into three eras: Paleozoic, Mesozoic, Cenozoic
Paleozoic Era
- 542 – 251 million years ago
- "Ancient Life"
- Characterized by the diversification of life - major animal groups including invertebrates, fish, amphibians, reptiles, and the first land plants emerged
Paleozoic Tectonic Events
- Rodinia supercontinent broke into Laurentia and Gondwana land.
- Gondwana moved towards the south pole.
- Laurentia moved towards the equator and continued moving.
- The continents collided at the end of the Carboniferous period to form Pangaea
Cambrian Period
- 541-485 million years ago
- Cambrian Explosion - rapid diversification of life
- Major Events:
- Predation became common amongst species
- Hard-shelled organisms emerged
- Trilobites, arthropods with hard exoskeletons
- Brachiopods, filter-feeding marine animals with two shells
- Crinoids, sea lilies related to starfish, sea urchins, and sea cucumbers
Ordovician Period
- 485 – 444 million years ago
- Diversity of marine invertebrates, including, mollusks, coelenterate, graptolites, trilobites, Eurypterid.
- Earliest vertebrates, ostracoderms, appeared
- First non-vascular plants appeared such as mosses and liverworts
- A major extinction event wiped out 60% of marine species, ending the Ordovician period.
Silurian Period
- 443 – 416 million years ago
- First jawed fish, Placoderm, evolved
- The first plants appeared on land
- The first terrestrial arthropods evolved
- Laurentia, Siberia, and Baltica moved towards each other at the equator forming Eurasia
- Early Silurian glaciers melted and sea level rose due to the greenhouse effect
Devonian Period
- 416 – 359 million years ago
- "Age of Fish" due to diverse fish
- The first ferns and tree-like plants appeared on land
- Bony fish became abundant
- First seed-bearing plants appeared
- The first ammonite appeared
Carboniferous Period
- 359– 299 million years ago
- Forests and swamps with seed plants on land
- Winged insects emerged
- Early amphibians lived on land
- Fish expanded in oceans, many mollusks and corals, but few trilobites
Permian Period
- Inland Seas were reduced due to the beginning of the collision of continents to form Pangaea.
- Land dried due to changes in glaciation and Pangaea
- Episodes of mountain building occurred
- Life in oceans diminished
- First vertebrate herbivores evolved on land (Eocasea)
- Many gymnosperm plants appeared
- 90% of marine species extinct at the end of the period
- Warming climate and dry interior of continents
Major Extinction Events
- Late Ordovician
- Late Devonian
- Late Permian and early Triassic
- The most notable event: Permian-Triassic Extinction, where almost 90% of species were lost, leaving only a few existing on land
Mesozoic Era
- "Middle Life"
- 252 – 66 million years ago
- "Age of Reptiles/Dinosaurs"
- Life diversified rapidly, giant reptiles, dinosaurs, and other large creatures roamed the Earth
Triassic Period
- 252 – 200 million years ago
- The rise of reptiles
- The first dinosaurs walked on land
- Late Triassic – early mammals first appeared
- The first dinosaur Nyasasaurus parringtoni appeared
Jurassic Period
- 200 – 145 million years ago
- Dinosaurs dominated the land
- The first birds appeared
- Pangaea began to break apart in the early Jurassic period
- Formation of the Atlantic Ocean began
- The first flowering plants, angiosperms, appeared
- The first bird, Archaeopteryx, appeared
Cretaceous Period
- 145– 66 million years ago
- Known for the dominance of iconic dinosaurs such as:
- Triceratops
- Tyrannosaurus Rex
- Pterosaurs
- Angiosperm dominance
- Marine reptile diversity
- Mammalian diversification
Cenozoic Era
- Divided into 3 periods: Paleogene, Neogene, Quaternary
- Present location of the continents and modern-day inhabitants, including humans, can be traced to this period.
Cenozoic Era
- 65 million years ago – present
- "Age of Mammals"
- Due to the extinction of many giant mammal groups, smaller species thrived and diversified because their predators were gone
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Description
Test your knowledge of Earth's history through the geological time scale! This quiz covers major eons including Hadean, Archean, and Proterozoic, along with key geological events and life forms from each period. Challenge yourself and learn more about the timeline of our planet.
