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Time Exhibit
Life Through Time Exhibit
Richard Paselk*
The development of life over the last 3,700 million years of the Earth's
history is one of the great stories told by modern science. During most
of this time living things left only traces to indicate their existence.
Then, about 544 million years ago, during what is referred to as the Cambrian
explosion, animals learned how to make hard, mineralized body parts. Suddenly
rocks resulting from sand and mud deposits become laden with fossil remains,
and our picture of ancient life grows enormously in scope and detail.
PRECAMBRIAN (ARCHEAN and PROTEROZOIC EONS):
4,570 to 542.0 Million years ago
The Precambrian encompasses nearly 90% of Earth's history, and almost
a third of the history of the Universe. It begins with the formation of
the Earth from the dust and gas of the solar nebula, includes the origin
and early evolution of life, the beginning of plate tectonics, and the
development of an oxygen atmosphere. It ends with one of Earth's great
extinction events, making way for the development of modern plants and
animals. Case #1. View
case index
PHANEROZOIC EON (542.0 Million years ago
to present):
Paleozoic Era (542.0 to 251.0 Million
years ago)
542.0 to 488.3 Million years ago
Sudden appearance of fossil remains referred to as the Cambrian explosion.
Marine animals with skeletons make their first appearance in shallow
seas. The domination of trilobites is reflected by the large number
in our exhibit, which also includes early brachiopods and burrows.
Case #2. View
case index
488.3 to 443.7 Million years ago
More complex shelled animals lived in seas during this period, which
ended in a mass extinction. Case #3. View
case index
443.7 to 416.0 Million years ago
A warm climate and high sea level gave rise to large reefs, while
on land simple land plants emerged. Case #4. View
case index
416.0 to 359.2 Million years ago
New predators such as sharks, bony fishes and ammonoids ruled the
oceans. On land, scorpions, spiders, wingless insects and the first
amphibians were starting to thrive. Case #5. View
case index
Carboniferous Period
359.2 to 299.0 Million years ago
359.2 to 318.1 Million years ago
During this period, sea lilies dominated the limestone seas and
reptiles began to appear along with ferns. Case #6. View
case index
318.1 to 299.0 Million years ago
Coal swamp forests thrived during this period. A dragonfly ancestor
lived then with a 29-inch wing inch. Case #7. View
case index
299.0 to 251.0 Million years ago
Reptiles started to thrive in water and on land and conifer forests
appear in this period. The Permian ended with greatest mass extinction
event known in Earth's history. Case #8. View
case index
Mesozoic Era (251.0 to 65.5 Million years ago)
251.0 to 199.6 Million years ago
The Permian extinction event was so severe that entirely new fauna
and flora appear in the Triassic. Mammals and dinosaurs started to
appear in this period. Case #9. View
case index
199.6 to 145.5 Million years ago
Ammonites and dinosaurs made a huge comeback after near extinction
at the end of the Triassic. The first bird fossils and flying pterosaurs
showed up in the fossil record. Case #10. View
case index
145.5 to 65.5 Million years ago
The first flowering plants appeared at the end of the Mesozoic era,
along with the extinction of dinosaurs, pterosaurs, mesosaurs and
ammonoids, to name a few. Case #11. View
case index
Cenozoic Era (65.5 Million years ago to present)
65.5 to 23.03 Million years ago
Primitive mammals and birds began to flourish. The Paleogene includes
what used to be the first part of the Tertiary. The Paleogene has
three divisions:
- Paleocene Epoch (65.5 to 55.8 Million years ago).
- Eocene Epoch (55.8 to 33.9 Million years ago)
- Oligocene Epoch (33.9 to 23.03 Million years ago).
Case #12. View
case index
23.03 Million years ago to present
Mammals evolved in oceans and on land. The Neogene now includes Geologic
time up to the present, covering what used to be the later Tertiary
and the Quaternary. The Neogene has four divisions:
- Miocene Epoch (23.03 to 5.332 Million years ago)
- Pliocene epoch (5.332 to 1.806 Million years ago)
- Pleistocene Epoch (1.806 to 0.0115 Million years ago)
- Holocene Epoch (11.5 thousand years ago to the present). The Holocene
may actually simply be the latest interglacial of the Pleistocene.
Case #13. View
case index
65.5 Million years ago to present
Six cases highlight major mammal groups found in North America over the entire Cenozoic.
Other Ways to Navigate the Life Through Time Exhibit
1. You can also explore the Museum's Life
Through Time Mural. The organisms on this mural are linked
to images of fossils of these organisms. The time line at the bottom of
the mural will lead to illustrated essays for each geological period.
2. View an interactive Geological
Timeline that serves as a key to the Life Through Time cases
in the museum.
Life Through Time Mural |
Geological Timeline |
*The Life Through Time exhibit web pages were researched, written and designed by Richard Paselk, associate curator.
Last modified 24 July 2008
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