Download Evolution (Fossils/Geologic Time) Review PO4 – Describe how rock

Evolution (Fossils/Geologic Time) Review
PO4 – Describe how rock and fossil record show that environmental conditions
changed over geologic and recent time.
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Geologic time = the summary of earth’s history, divided into intervals of time
defined by major events or changes on Earth; measured in thousands, millions,
and billions of years
PO5 – Describe the conditions necessary for fossils to form.
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The organism or trace of the organism must be preserved before it decomposes
or disappears so it must be covered or buried in sediment rather quickly and then
as the layers of sediment harden together over time creating sedimentary rock
PO6 – Distinguish among the different types of fossils.
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Fossil = a trace or the remains of a once-living thing from long ago
Index fossil = a fossil of an organism that was common, lived in many areas, and
existed only during a certain span of time; used to determine the age of rock
layers
Trace fossil = evidence of an animal’s presence in a given location such as
footprints, trails, holes, and feces
Body fossil = a fossil of an actual body part such as teeth or bones
Cast fossil = a solid model in the shape of an organism made when a mold
becomes filled with minerals
Mold fossil = a visible shape left after an animal or plant was buried in sediment
and then decayed away
PO7 – Name some common types of organisms from each era of geologic time.
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Paleozoic = means ‘ancient life’; fish, reptiles, insects, ferns
Mesozoic = means ‘middle life’; dinosaurs, mammals, birds, flowering plants
Cenozoic = means ‘recent life’; called the Age of Mammals because mammals
became a main category of life on Earth
PO8 – Explain why Precambrian Era has a poor fossil record.
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Precambrian time = the Hadean, Archaen, and Proterozoic eons together and
make up almost 90% of Earth’s history
 Very few plants or animals existed and most that did were single-celled and
microscopic; many had soft bodies that rarely form fossils; the planet was
dominated by volcanoes (igneous rock) which never contain fossils; fossils form in
sedimentary rock
PO9 – Explain how scientists determine the age of fossils.
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Relative Age = the age of an event or object in relation to other events or objects
Absolute Age = the actual age of an event or object
Radioactive or radiometric dating = a technique used to date materials such as
rocks comparing amounts of radioactive isotopes and decay products using
known decay rates
 Half life = the length of time it takes for half of the atoms in a sample of
radioactive element to change from an unstable form into another form
Other Vocabulary
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Evolution = the process through which species change over time
Extinction = the permanent disappearance of a species
Mass Extinction = one of several periods in Earth’s history when large numbers
of species became extinct at nearly the same time
Natural selection = the process through which members of a species that are
best suited to their environment survive and reproduce at a higher rate than
other members of the species
Adaptation = a characteristic, a behavior, or any inherited trait that makes a
species able to survive and reproduce in a particular environment
Eon = the largest unit of geologic time; Earth’s history is divided into 4 eons
(Hadean, Archean, Protozoic, Phanerozoic)
Era = Eons are divided into Eras such as the Phanerozoic Eon is divided into the
Paleozoic, Mesozoic, and Cenozoic Eras
Period = each Era is subdivided into a number of Periods such as the Mesozoic
Era is divided into the Triassic, Jurassic, and Cretaceous periods
Epoch = the periods of the Cenozoic Era are divided into Epochs