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Dinosaur Home  A-Z Dinosaurs List Graph
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What is Evolution?
In a nutshell, it is a theory that many different
forms of one species are created, but |
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only the ones
with advantages survive to reproduce, and spread
these advantages.These advantages could include
better camouflage, more strength, better eyesight,
and so forth.Slowly, over many generations, the
simple single-celled life forms, evolved into
more and more complex multiple-celled organisms,
adapting to the changing environment of the earth.
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Past life is often referred
to being a part of a certain era, or a certain
point on the geological timescale. |
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There are 6 eras
on the geological timescale, consisting of the
Hadean, Archaean, Protezoic, Paleozoic, Mesozoic,
and the Cenozoic.
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Hadean:
The Hadean era did not contain life as
we know it, but rather the building blocks
of life, such as amino acid, proteins
and the like, mentioned previously. It
lasted approximately from 3.8 to 4.5 billion
years ago.
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Archaean:
This era took place from about 3.8 to
2.5 billion years ago and also saw the
formation of the first cells, as described
in the ’The First Cell’ section.
Also, it is likely that approximately
70% of the world's landmasses where created
during this era.This era saw the creation
of simple bacteria and plant like algae,
which could actually feed off pure energy
in the form of sunlight. They became the
building blocks for evolution of life,
and the basis of early food chains.
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Protezoic:
This era took place approximately 2.5
billion to 544 million years ago. Many
fossils have been found from this Era,
mostly in the form of Bacterial life and
Archaean life (Archaeans are physically
similar to bacteria, but are biochemically
different so much that they are considered
a separate from bacteria. They are known
for living in very extreme environments)
About 1.8 billion years ago, eukaryotic
cells began to appear (Eukaryotic cells
are ones containing a nucleus, which stores
genetic information. Eukaryotic cells
are contained in many species today, such
as plants, fungi, animals, insects and
so forth.) Another important event in
the Proterozoic era was the first evident
of oxygen buildup in the atmosphere. This
meant death for early bacteria, which
could not survive in oxygen environments,
but allowed eukaryotic cells to thrive.The
end of this era also saw the beginnings
of multi-cellular life forms, such as
certain algae and simple animals.
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Paleozoic:
During the Paleozoic era, many life forms began
to flourish. Many of these life forms we would
not recognize today. These life forms slowly evolved
in the ocean, and began to step out onto land,
originally with amphibious life forms, and eventually
with reptiles.Marking the end of this era, here
was the mass Permian extinction, approximately
245 million years ago, in which many of the life
forms that once flourished died off.
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Mesozoic:
The Mesozoic era has three time periods. The cretaceous
(146-65 mya), the Jurassic (208-146 mya) and the
Triassic (245-208) Mesozoic carries the meaning
of middle animals. The Mesozoic saw the creation
of many different life forms, including the famous
dinosaurs. There where also many new plants, including
early coniferous plants. However, many of these
life forms succumbed to extinction, or evolution,
and are not around today in the form they originally
where.
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Cenozoic.
The Cenozoic is the most current era, taking place
from the last mass extinction of all land-based
dinosaurs (approximately 65 million years ago)
to the present day. This era saw the rise of many
mammals, such as whales, the great hunter cats,
as well as Humans. But it also saw the rise of
the birds, insects, and many new plants, including
flowering plants. Much of life as we know it today
evolved during this era.
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