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Influence of Catastrophes on Earth’s
History
Earliest life forms were influenced by:
The forming atmosphere and oceans
Volcanic activity
Mountain building
Life on land developed and flourished in
tropical climates, but many life-forms
became extinct at the end of the
Paleozoic era (fish and reptiles still
survived
Mesozoic Era events:
Reptiles, birds, mammals thrived
Ended with a mass extinction (dinosaurs
became extinct)
Extinction theories include impact
catastrophe with climate change
Cenozoic Era events:
Climatic changes- Ice Ages
Species still thrived
Geologic Time Scale Divisions: Era, Periods, Epochs
Geologic Time Scale divides Earth’s long history into units
of time.
Eras Periods Epochs
OLDEST TO RECENT
Eras
Periods
Precambrian
Cambrian1st period
Epochs
Description
Earliest era
Paleozoic
Mesozoic
Cenozoic
Quaternary
Holocene
Present Day
Illustrate the vast diversity of life
that has been present on Earth
over time by using the geologic
time scale.
Geologic Time Scale- is a
record of the major events
and diversity of life forms
present in Earth’s history.
At the end of each era, a
mass extinction occurred
Paleozoic Era:
Mass extinction killed most invertebrates and
amphibians
Examples of Invertebrates: Trilobites, Brachiopods
Trilobites are an extinct group
of arthropods with hard,
jointed external skeletons,
distantly related to crabs,
scorpions, and insects. They
are among the most familiar
fossils of the Paleozoic Era,
about 545-250 million years
ago. "The majority of trilobites
were between three and ten
centimetres long," notes Dave
Rudkin, assistant curator of
paleobiology at the Royal
Ontario Museum in Toronto.
"Their fossil remains are
eagerly sought by amateur and
professional paleontologists
alike."
Brachiopods are marine animals
that, upon first glance, look like
clams. They are actually quite
different from clams in their
anatomy, and they are not closely
related to the molluscs. They are
lophophorates, and so are related
to the Bryozoa and Phoronida.
Although they seem rare in today's
seas, they are actually fairly
common. However, they often
make their homes in very cold
water, either in polar regions or at
great depths in the ocean, and thus
are not often encountered. There
are about 300 living species of
brachiopods.
Mesozoic Era:
The mass extinction
at the end of the era
caused the dinosaurs
to become extinct
Cenozoic Era:
New mammals appear while other
mammals became extinct
Diversity of life forms increased
Flowering plants became most common
Humans are part of the most recent
period in this era