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Questions and Answers
What are the two main categories explaining the Cambrian Explosion?
What are the two main categories explaining the Cambrian Explosion?
Which of the following is an intrinsic factor believed to have impacted the Cambrian Explosion?
Which of the following is an intrinsic factor believed to have impacted the Cambrian Explosion?
How do Hox and Hox-like genes relate to the Cambrian Explosion?
How do Hox and Hox-like genes relate to the Cambrian Explosion?
What extrinsic change might have influenced the Cambrian Explosion?
What extrinsic change might have influenced the Cambrian Explosion?
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If animals had genetic mechanisms for complexity before the Cambrian, what is a reason they may not have exhibited large forms?
If animals had genetic mechanisms for complexity before the Cambrian, what is a reason they may not have exhibited large forms?
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What significant event is characterized by the relatively sudden appearance of diverse animal forms in the fossil record around 450 million years ago?
What significant event is characterized by the relatively sudden appearance of diverse animal forms in the fossil record around 450 million years ago?
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Which type of fossil represents the first fossil evidence of many animal phyla during the early Cambrian period?
Which type of fossil represents the first fossil evidence of many animal phyla during the early Cambrian period?
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What does the term 'Lagerstätten' refer to in the context of fossil preservation?
What does the term 'Lagerstätten' refer to in the context of fossil preservation?
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Which factor primarily explains the diversification of bilaterians during the Cambrian period?
Which factor primarily explains the diversification of bilaterians during the Cambrian period?
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Which of the following animals belongs to the Burgess Shale fauna?
Which of the following animals belongs to the Burgess Shale fauna?
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What is a major reason that the Cambrian Explosion raises questions among scientists?
What is a major reason that the Cambrian Explosion raises questions among scientists?
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When did the origin of bilaterians likely occur according to molecular clock arguments?
When did the origin of bilaterians likely occur according to molecular clock arguments?
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What aspect of early multicellular life was largely absent in pre-Cambrian fossil records?
What aspect of early multicellular life was largely absent in pre-Cambrian fossil records?
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What was a factor that limited the evolution of large active animals during the Ediacaran period?
What was a factor that limited the evolution of large active animals during the Ediacaran period?
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What is one plausible explanation for the diversification of animal forms at the start of the Cambrian?
What is one plausible explanation for the diversification of animal forms at the start of the Cambrian?
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What ecological factor might have contributed to widespread co-evolution during the Cambrian explosion?
What ecological factor might have contributed to widespread co-evolution during the Cambrian explosion?
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Which of the following questions remains unanswered regarding the Cambrian explosion?
Which of the following questions remains unanswered regarding the Cambrian explosion?
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Why is the timing of the rise in oxygen significant in the context of animal diversification?
Why is the timing of the rise in oxygen significant in the context of animal diversification?
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What feature is associated with the 'arms race' in the ecological explanation for Cambrian diversification?
What feature is associated with the 'arms race' in the ecological explanation for Cambrian diversification?
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What aspect of multicellularity is suggested as having evolved due to environmental factors?
What aspect of multicellularity is suggested as having evolved due to environmental factors?
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How did the atmosphere of the Earth during the Ediacaran affect the types of animals that existed?
How did the atmosphere of the Earth during the Ediacaran affect the types of animals that existed?
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Study Notes
The History of Life
- Earth formed approximately 4.6 billion years ago.
- The Hadean Eon (4600-3850 Ma) was a period from the origin of the solar system to approximately 3850 Ma.
- The Hadean Eon had almost no geologic record.
- Key events of the Hadean Eon include: differentiation of earth into crust, mantle & core; origin of the atmosphere; condensation of water; & origin of continental crust.
Geologic Time Scale
- The Phanerozoic Eon is broken down into the Cenozoic, Mesozoic, and Paleozoic Eras, each with periods and epochs.
- The Cenozoic Era includes the Quaternary Period (Holocene & Pleistocene Epochs), Neogene Period (Miocene & Oligocene Epochs), and Paleogene Period (Eocene & Paleocene Epochs).
- The Mesozoic Era includes the Cretaceous, Jurassic, and Triassic Periods.
- The Paleozoic Era includes the Carboniferous, Devonian, Silurian, Ordovician, and Cambrian Periods.
- The Precambrian includes the Proterozoic and Archean Eons and Hadean(earlier).
The Archean (3850-2500 Ma)
- Origin of life (approximately 3800 Ma).
- Early organisms used methane, sulfate, and hydrogen sulfide based metabolisms, producing CO2 and alcohol as byproducts.
- Photosynthetic organisms appeared approximately 3500 Ma.
- An oxygen environment developed between 3,500 and 2,800 Ma.
What is "Life"?
- Attributes of life include autonomous replication (mitosis, meiosis); critical levels of complexity (simpler subunits into multiple complex combinations); and the ability to evolve via natural selection.
- Requirements of life include an energy source, basic chemicals (nucleic acids, proteins, minerals), and an external environment that sustains life.
The Proterozoic (2500-542 Ma)
- Origin of eukaryotes (1500 Ma).
- Rapid diversification of soft-bodied multicellular animals and green algae (1500-600 Ma).
- Eukaryotic cells have a nucleus, DNA storage, RNA transcription, and membrane-bound organelles.
Serial Endosymbiosis Theory (SET)
- Eukaryotic cells evolved when aerobic bacteria infected or were engulfed by a larger host cell and later established a symbiotic relationship.
- Mitochondria are thought to be derived from purple bacteria.
- Chloroplasts are thought to be derived from cyanobacteria.
Cambrian Explosion
- The Cambrian explosion (approximately 542-530 million years ago) saw a relatively sudden appearance of diverse animal forms in the fossil record.
- Explanations include intrinsic changes in animal development and extrinsic changes in the environment.
Challenges of Multicellularity
- Increasing size necessitates greater support, rigidity, and more complex reproduction.
- Surface to volume ratio (S/V) decreases with size leading to exchange limitations (gasses, nutrients). Multicellular organisms develop ways to deal with these limitations using larger surface areas such as in the circulatory system and lungs, or by adjusting the ratio utilizing shape.
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Description
Explore the fascinating history of life on Earth, from the formation of the planet to the major eons and eras that have shaped our geological history. This quiz will guide you through key events of the Hadean Eon, the divisions of the Phanerozoic Eon, and the intricate details of the Cenozoic, Mesozoic, and Paleozoic Eras.
