Transcript Evolution3_Compressed

Evidence from
meteorites and
radioactive isotopes
found in the earth’s
crust
http://universe-review.ca/10-36-Humanevo.jpg
Oldest known hominid
(artistic portrayal), discovered
recently (July 2002) in northern
Chad, Africa with a complete
cranium and dated back to nearly
seven million years ago.
Sahelanthropus tchadensis. It is
generally believed that humankind
had its roots in Africa
http://universe-review.ca/I10-36-oldesthominid.jpg
http://universe-review.ca/I10-36-familytree.jpg
Evolution =
Mutation +
Natural Selection
“Other” Mechanisms:
• Mass Extinctions
• Cambrian Explosion
http://universe-review.ca/I10-70-selection.jpg
From the site http://universe-review.ca
30% of the genera
wiped out! The
suspected causes include
severe volcanism
and global
warming. Plenty of
From the site http://universe-review.ca
groups, including small
predatory dinosaurs, the
early mammals, and
some crocodile relatives
survived into the
Jurassic. Yet large
groups of archosaurs
mysteriously vanished.
It really isn't obvious
why the non-dinosaurs
get hammered the most.
Anyway, the end-Triassic
extinction pruned a
number of dinosaurs,
but the group as a whole
marched on, and
prospered in the Jurassic
period.
From the site http://universe-review.ca
http://universe-review.ca/R10-19-animals.htm
Dinosaurs became dominant, reaching their largest size. The brontosaurus (thunder lizard) was a huge
sauropod with length up to 80 feet and a total weight of 30 to 35 tons. The large size probably helped them to escape
predation by carnivorous dinosaurs. In the same picture, the stegosaur protected itself by the elaborate armour. Its small brain was compensated by
large ganglia (a mass of never cells) between the shoulders and another one above the hips; those are sometimes referred to as the second brain.
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From the site http://universe-review.ca
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Molecular Clocks
Study of DNA variation among different species provides another way to
classify them as shown by the tree of life in the figure above. According to this scheme
the common ancestor at the base of the tree gave rise to three branches: microbes
known as archaea (primitive unicellular organisms that live in most extreme
environments), bacteria (unicellular organisms without nucleus or cell structure), and
eukaryotes (any organism with one or more cells that have visible nucleus and
organelles). The lengths of the branches reflect how much the DNA of each lineage has diverged from
their common ancestor. They demonstrate that most of life's genetic diversity turns out
to be microbial; the entire animal kingdom (shown at the upper right) are just a few twigs
at one end of the tree.
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11-cis-retianal  trans-retinal  rodopsin changes shape  makes opsin sticky to transducin 
GDP from transducin falls off and replaced by GTP  activated opsin binds to phosphodiesterase
which aqcuires the ability to cut cGMP  lower cGMP conc. causes ion channels to close lowering
Na concentration in cell and lowers cell potential  current transmitted down optic nerve to brain
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The Cambrian
“Explosion”
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http://universe-review.ca/F10-multicell.htm#animals
“There is another and allied difficulty, which is much more serious. I allude to the manner in which species
belonging to several of the main divisions of the animal kingdom suddenly appear in the lowest known
fossiliferous rocks. Most of the arguments which have convinced me that all the existing species of the same
group are descended from a single progenitor, apply with equal force to the earliest known species. For instance, it
cannot be doubted that all the Cambrian and Silurian trilobites are descended from some one crustacean, which must
have lived long before the Cambrian age, and which probably differed greatly from any known animal. Some of the
most ancient animals, as the Nautilus, Lingula, etc., do not differ much from living species; and it cannot on our
theory
be supposed, that these old species were the progenitors of all the species belonging to the same groups which have
subsequently appeared, for they are not in any degree intermediate in character. Consequently, if the theory be true, it
is indisputable that before the lowest Cambrian stratum was deposited long periods elapsed, as long as, or probably
far longer than, the whole interval from the Cambrian age to the present day; and that during
these vast periods the
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“To the question why we do not find rich fossiliferous deposits belonging to these assumed earliest periods prior to the
Cambrian system, I can give no satisfactory answer. Several eminent geologists, with Sir R. Murchison at their head, were
until recently convinced that we beheld in the organic remains of the lowest Silurian stratum the first dawn of life. Other
highly competent judges, as Lyell and E. Forbes, have disputed this conclusion. We should not forget that only a small
portion of the world is known with accuracy….. The several difficulties here discussed, namely, that, though we find in
our geological formations many links between the species which now exist and which formerly existed, we do not find
infinitely numerous fine transitional forms closely joining them all together. The sudden manner in which several groups
of species first appear in our European formations, the almost entire absence, as at present known, of formations rich in
fossils beneath the Cambrian strata, are all undoubtedly of the most serious nature…”
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http://universe-review.ca/R10-19-animals.htm
600 mya  rise of Edicarian “fauna”: at various times they have been considered algae, lichens,
giant protozoans, or even a separate kingdom of life unrelated to anything living today. A novel
explanation suggests that the Ediacaran fossils weren't animals at all. Rather, they were probably
lichens.
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… an artist's impression of the Cambrian scenery at the Burgess Shale
halfway up Mt. Field, British Columbia. More than 120 different species of
animal fossils have been found there. Some of those shown in the drawing
are: sponges, cnidarians, worms, trilobites, anomalocaris, marrella,
hallucigenia, sea scorpions, and brachiopods.
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There is still much
controversy over the
significance of the
Burgess and
Chengjiang fossils.
What is certain is
that the
transformation of
life from singlecelled organisms to
multicellular
organisms was swift,
sudden and
widespread.
Another fine bed of early Cambrian fossils exists in Chengjiang, China. This site contains similar type
of fossils to those found in the Burgess Shale, and date to around 530 million years old (about 20
million years older than the Burgess Shale fauna). They are the oldest such fossils ever found and
contain organisms with soft body parts. Paleontologists have extracted over 100 species of trilobites,
worms, sponges and various ancestors of crustaceans, spiders, insects and probable early chordates, as
well as numerous problematical forms that cannot definitely be assigned to well established taxa.
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Unicellular Organisms
Research in 2004 attributed the complexity of multicellular
organism to the use of RNA based regulatory signals.
The Cambrian explosion was related to the abrupt
addition of this genetic regulatory system. The
figure above shows the complexity of eubacteria and archaea
at low levels over the past billion years up to the present.
While the complexity in eukaryote organisms advanced
gradually up to a ceiling and then increased abruptly at the
Cambrian explosion when a new regulatory system became
available.. The proliferation of complex life forms some 20
million years prior to the Cambrian explosion might be just
the initial trials to become multicellular.
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