Tip:
Highlight text to annotate it
X
{\rtf1\ansi\deff0\adeflang1025 {\fonttbl{\f0\froman\fprq2\fcharset0 Times
New Roman;}{\f1\froman\fprq2\fcharset2 Symbol;}{\f2\fswiss\fprq2\fcharset0 Arial;}{\f3\fnil\fprq0\fcharset0 Times New
Roman;}{\f4\fnil\fprq0\fcharset0 Arial;}{\f5\fnil\fprq2\fcharset0 Microsoft YaHei;}{\f6\fnil\fprq2\fcharset0
Mangal;}{\f7\fnil\fprq0\fcharset128 Mangal;}} {\colortbl;\red0\green0\blue0;\red128\green128\blue128;}
{\stylesheet{\s0\snext0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033 Default;}
{\s15\sbasedon0\snext16\sb240\sa120\keepn\hich\af5\dbch\af6\afs28\loch\f2\fs28 Heading;}
{\s16\sbasedon0\snext16\sb0\sa120 Text body;} {\s17\sbasedon16\snext17\sb0\sa120\dbch\af7
List;} {\s18\sbasedon0\snext18\sb120\sa120\noline\i\dbch\af7\afs24\ai\fs24
Caption;} {\s19\sbasedon0\snext19\noline\dbch\af7 Index;}
}{\info{\creatim\yr2013\mo2\dy17\hr15\min33}{\revtim\yr0\mo0\dy0\hr0\min0}{\printim\yr0\mo0\dy0\hr0\min0}{\comment OpenOffice.org}{\vern3400}}\deftab709
{\*\pgdsctbl {\pgdsc0\pgdscuse195\pgwsxn12240\pghsxn15840\marglsxn1134\margrsxn1134\margtsxn1134\margbsxn1134\pgdscnxt0
Default;}} \formshade\paperh15840\paperw12240\margl1134\margr1134\margt1134\margb1134\sectd\sbknone\sectunlocked1\pgndec\pgwsxn12240\pghsxn15840\marglsxn1134\margrsxn1134\margtsxn1134\margbsxn1134\ftnbj\ftnstart1\ftnrstcont\ftnnar\aenddoc\aftnrstcont\aftnstart1\aftnnrlc
\pgndec\pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{{\*\bkmkstart internal-source-marker_0.7805400278884917}{\*\bkmkend
internal-source-marker_0.7805400278884917}\rtlch \ltrch\loch
This is Earth. It is filled with life, ranging from the simplest bacteria to modern humans.
While we do not know exactly how or when life first appeared on earth, we do know that it
was somewhere around 3.8 billion years ago in an era known as the Archean, and that over
the course of those billions of years it evolved to its current state of abundance and complexity.
This was an incredibly slow process, fraught with many twists and turns. The history of
the evolution of life is normally described as gradual and monotonous, with little to
no action occurring on a humanly comprehensible timescale.}
\par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch \ltrch\loch
} \par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch
\ltrch\loch Throughout most of the earth's history, this
is an accurate description of the evolutionary} \par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch
\ltrch\loch process. However, there are several instances
that contradict this notion. Over the eons, numerous mass extinctions and other monumental
events have caused massive upheaval and reform as they shifted the planet towards the world
we know today. However, there was one such transpiration without which the incredible
story of the evolution of life would ever have been told.}
\par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch \ltrch\loch
} \par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch
\ltrch\loch When the earth first formed, it was a hellish
place, with a surface of lava, poisonous air, and no liquid water. Meteorites bombarded
the surface constantly, vaporizing any primeval life forms. Billions of years later, after
the surface cooled and oceans formed, an inanimate soup of organic molecules began to self-organize,
and became the first life on Earth. This life was very simple, lacking almost all of the
structures that characterize modern cells, such as a nucleus and mitochondria. Over billions
of years, life slowly began to change and grow in complexity, but even after 3.3 billion
years of evolution, the Earth\'92s biosphere consisted of only a slew of microbes and a
few sparse and unimpressive invertebrates.} \par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch
\ltrch\loch }
\par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch \ltrch\loch
Life on earth was predicated on self-replicating reactions among\line proteins and RNA.\line
} \par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch
\ltrch\loch While life had lain stagnant for much of the
earth\'92s history, all of that was about to change in a relative blink of an eye. Approximately
540 million years ago, in a time period known as the Cambrian, the diversity and abundance
of life began to skyrocket, transforming an essentially dead planet into a world abounding
with wondrous animal forms. This revolutionary event, known as the Cambrian Explosion, was
solely responsible for the creation of all animal groups that exist today, including
arthropods, mollusks, and chordates, which includes the mammals and humans. Nevertheless,
340 million years ago these creatures looked nothing like their descendants do today. Fish,
reptiles, octopi, and insects all had yet to evolve.}
\par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch \ltrch\loch
} \par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch
\ltrch\loch Instead, there were the trilobites... Pikaia...
Wiwaxia... the 5-eyed Opabinia, and many other strange and wondrous creatures. The top predator
of this ancient sea was the deadly Anomalocaris.} \par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch
\ltrch\loch }
\par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch \ltrch\loch
These creatures were the product of an incredible event. Within a mere 30 million years, life
diversified more it had during all of the aeons since it first appeared. .. Despite
much debate over the specific causes, enough is known to conclusively say that without
the Cambrian Explosion, or another similar revolution, none of the Earth\'92s modern
animals would have come into existence.} \par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch
\ltrch\loch }
\par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch \ltrch\loch
One of the most well known and prevalent classes of animals during the Cambrian were the trilobites:
primitive arthropods that that were one of the most successful and widespread organisms
of all time. They were important not only because of }{{\*\bkmkstart __DdeLink__97_1180081595}{\*\bkmkend
__DdeLink__97_1180081595}\rtlch \ltrch\loch their success as a species, but how they interacted
with other species. Trilobites were the weavers of the Earth\'92s first food web, in which
predator, producer and prey all struggled for survival for the first time. Battles were
fought by a simple code: eat or be eaten. Competition among all of these new animals
further accelerated the evolutionary process, and laid the groundwork for how life on Earth
would progress for the next half a billion years.}
\par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch \ltrch\loch
} \par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch
\ltrch\loch In this new world , the top predator was a
strange creature called Anomalocaris Canadensis.} \par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch
\par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch \ltrch\loch
Anomalocaris is thought to be a vicious predator. They might have gotten to be up to a meter
long, so they'd be big, and they'd be able to crunch on things, And there are a lot of
trilobites, similar to this one, that have a bite mark taken out of them that matches
the mouth of Anomalocaris, so you can match those up and think, "The animal bit the trilobite,
and left the bite mark."} \par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch
\ltrch\loch }
\par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch \ltrch\loch
A lesser-known, and yet equally important species, was Pikaia gracilens, the oldest
known ancestor of modern vertebrates, and by extension, humans. It was also the first
animal to have a head-like structure, including various sensory organs and a spinal cord.
While Pikaia was not of incredible importance to the ecosystems of the Cambrian, its vertebrate
descendants would later come to dominate the entire world during the rest of the Phanerozoic
The Cambrian Explosion caused massive reforms in the paleontological sciences. Animal fossils
from the Cambrian had been discovered as early as the 1830\'92s by Adam Sedgwick and Roderick
Murchison in a series of rocky outcrops in Cambria, from which the Cambrian period derives
its name.} \par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch
\ltrch\loch }
\par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch \ltrch\loch
These fossils did not receive much attention until 1909, when Charles Walcott discovered
massive fossil beds of Cambrian animals in the Burgess shale formation in the Rocky Mountains.
He collected some 65,000 fossils over the course of twenty years, and within a few decades,
the huge deposits of exceptionally well-preserved fossils made the significance of the Cambrian
fauna undeniable.} \par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch
\ltrch\loch }
\par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch \ltrch\loch
The apparent rate of evolution shown by the Burgess shale fossils was quite a shock to
the scientific community. Scientists thought evolution only occurred at incredibly slow
rates over immense timescales, but this new evidence contradicted their ideas. Charles
Darwin, founder of the theories of Evolution and Natural Selection, went as far as to consider
the explosion a possible counterargument to his theories. In recent years, more accurate
methods of geological dating and the discovery of Precambrian microfossils have reduced the
apparent rate of evolution to more reasonable levels, but the Cambrian Explosion\'92s impact
both on the planet and the sciences remains enormous.}
\par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch \ltrch\loch
} \par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch
\ltrch\loch The Cambrian explosion is really a time that
allows us to mark when fossils were solid and heavily built, and therefore could leave
an external fossil skeleton. And so the reasons for that could be a change in ocean chemistry;
a change in water chemistry. It could also be the release of methane from a methane ice
that was deep in the ocean. Even though we do not know why the Cambrian Explosion happened,
we do know that it did happen, and we'd like to strive for an explanation for that as well.}
\par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch \ltrch\loch
} \par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch
\ltrch\loch While the Cambrian Explosion created untold
multitudes of new forms of life, it produced a reaction that brought its fair share of
death as well. Before the Cambrian, in the Proterozoic aeon, most life consisted of large
mats of microbes living in symbiotic colonies. These structures were originally responsible
for oxygenating our atmosphere, as they absorb carbon dioxide and emit molecular oxygen,
which is poisonous to them. Since their first appearance more than 3.5 billion years ago,
the scarcity of macroscopic, mobile organisms meant that there was little to disturb these
fragile colonies. However, once the advanced fauna of the Cambrian started spreading throughout
the seas, these microbial mats were often damaged by the increased bioturbation from
all of the organisms walking and swimming overhead, as well as the holes produced by
burrowing organisms such as Ottoia. This not only damaged the colonies physically, but
saturated the ocean floor with oxygen-rich sea water which killed off the oxygen-intolerant
microbes. As complex organisms invaded the seas, they created a reaction that transformed
the planet into the place we know today. } \par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch
\ltrch\loch }
\par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch \ltrch\loch
While microbial mats still flourish, most of those living in shallow, seas were trampled,
burrowed, and choked to death, in what became known as the Cambrian Substrate Revolution.}
\par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch \ltrch\loch
} \par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch
\ltrch\loch Once the complexity had increased to a certain
extent, it was a matter of finding niches, and the niches are manifold, and as long as
life can evolve and change, niches will be filled. So, here we are, looking at chemicals...
we\'92re looking at the boundary, in time, between life and no life.}
\par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch \ltrch\loch
} \par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch
\ltrch\loch As our epic journey through the past draws
to a close, we can truly come to appreciate exactly how profoundly our world has been
affected by ancient revolutions. Every macroscopic organism that exists today, including us,
owes their life to the events of the Cambrian. Now, pause a while, and think about the incredible
changes that occurred in this ancient era. Think of the trilobites, swimming and crawling
through the water; of Anomalocaris, the terrifying apex predator; and of Pikaia, ancestor of
all modern vertebrates. Think of Wiwaxia, Opabinia, Ottoia, and all of the other extraordinary
creatures that once shaped our world. We all owe our existence to the life of ages past,
but above all, we must acknowledge the eminence of this fundamental revolution that we call
the Cambrian Explosion.} \par \pard\plain \s0\nowidctlpar{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\cf0\kerning1\hich\af8\langfe2052\dbch\af6\afs24\lang1081\loch\f0\fs24\lang1033{\rtlch
\par }