________- are the remains or traces of prehistoric life.
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Angiosperms
________- flowering plants with covered seeds- replaced gymnosperms as the dominant land plants.
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Carbonization
________ is particularly effective in preserving leaves and delicate animals.
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Earth
________ is much older than anyone had previously imagined and that its surface and interior have been changed by the same geological processes that continue today.
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Laurasia
________- is the continental mass that formed the northern portion of Pangaea, consisting of present- day North America and Eurasia.
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Radioactivity
________- is the spontaneous decay of certain unstable atomic nuclei.
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population of organism
○ It refers to the cumulative change in a(n) ________ over time.
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columns of calcium
They are distinctively layered mounds or ________ carbonate.
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Gymnosperms
________ are seed- bearing plants that do not depend on free- standing water for fertilization.
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Trace fossils
________ are indirect evidence of prehistoric life.
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Oxygen
________ began to accumulate in the atmosphere about 2.5 billion years ago.
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Eons
________- represent the greatest expanses of time.
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Uniformitarianism
________- the forces and processes that we observe today have been at work for a very long time.
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Molds
________ and casts are another common type of fossil.
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Correlation
________- is establishing the equivalence of rocks of similar age in different areas.
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Mammals
________- animals that bear live young and maintain a steady body temperature- replaced reptiles as the dominant land animals in the Cenozoic era.
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fine sediment
It occurs when an organism is buried under ________.
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Shields
________ are large, relatively flat expanses of ancient metamorphic rock within the stable continental interior.
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geological change
Revived Hutton's principle of slow ________, and presented a classic explanation of development over millions of years.
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water dwelling
The elimination of a(n) ________ stage (like the tadpole stage in frogs) was an important evolutionary step.
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Radiocarbon Dating
________- is the method for determining age by comparing the amount of carbon- 14 to the amount of carbon- 12 in a sample.
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◆ Dinosaurs
________ were land- dwelling reptiles that thrived during the Mesozoic era.
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Earths original atmosphere
________ was made up of gases similar to those released in volcanic eruptions today- water vapor, carbon dioxide, nitrogen, and several trace gases, but no oxygen.
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Radiometric dating
________ has supported the ideas of James Hutton, Charles Darwin, and others who inferred that geologic time must be immense.
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Law of superposition
________- states that in an undeformed sequence of sedimentary rocks, each bed is older than the one above it and younger than the one below it.
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negative electrical charges
◆ Orbiting the nucleus are electrons, which are ________.
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accurate radiometric date
A(n) ________ can be obtained only if the mineral remained in a closed system during the entire period since its formation.
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angular unconformity
A(n) ________ indicates that during the pause in deposition, a period of deformation (folding or tilting) and erosion occurred.
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radioactive isotope
Each ________ has been decaying at a constant rate since the formation of the rocks in which it occurs.
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Inclusions
________ are rocks contained within other rocks.
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Cenozoic era
◆ The ________ is divided into two periods of very unequal duration, the Tertiary period and the Quaternary period.
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Half life
________- is the amount of time necessary for one- half of the nuclei in a sample to decay to a stable isotope.
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geological events
Rocks record ________ and changing life forms of the past.
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important components of sediment
They are ________ and sedimentary rocks.
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gymnosperms
The ________ quickly became the dominant plants of the Mesozoic era.
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Relative dating
tells us the sequence in which events occurred, not how long ago they occurred
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Law of superposition
states that in an undeformed sequence of sedimentary rocks, each bed is older than the one above it and younger than the one below it
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Principle of Original Horizontality
means that layers of sediment are generally deposited in a horizontal position
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Principle of Cross-Cutting Relationships
states that when a fault cuts through rock layers, or when magma intrudes other rocks and crystallizes, we can assume that the fault or intrusion is younger than the rocks affected
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Correlation
is establishing the equivalence of rocks of similar age in different areas
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Fossils
are the remains or traces of prehistoric life
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Unaltered Remains
Some remains of organisms-such as teeth, bones, and shells-may not have been altered, or may have changed hardly at all over time
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Two conditions are important for preservation
rapid burial and the possession of hard parts
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The principle of fossil succession
states that fossil organisms succeed one another in a definite and determinable order
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Index Fossils
are widespread geographically, are limited to a short span of geologic time, and occur in large numbers
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Interpreting Environments
Fossils can also be used to interpret and describe ancient environments
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Radioactivity
is the spontaneous decay of certain unstable atomic nuclei
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Half-life
is the amount of time necessary for one-half of the nuclei in a sample to decay to a stable isotope
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Radiocarbon Dating
is the method for determining age by comparing the amount of carbon-14 to the amount of carbon-12 in a sample
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◆ There are three eras within the Phanerozoic eon
the Paleozoic, which means "ancient life," the Mesozoic, which means "middle life," and the Cenozoic, which means "recent life."
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Stromatolites
The most common fossils
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Following the long Precambrian, the most recent 540 million years of Earths history are divided into three eras
Paleozoic, Mesozoic, and Cenozoic
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Laurasia
is the continental mass that formed the northern portion of Pangaea, consisting of present-day North America and Eurasia
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Angiosperms
flowering plants with covered seeds-replaced gymnosperms as the dominant land plants