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Lecture 10

Lecture 10

Biological Sciences
Course Code
Herbert Kronzucker

of 8
Lecture 10
November 17 2008
The important recognition that some 99% of all the species that have existed on the planet over
history have vanished. The number of species today estimated to be alive is 32 to 100 and some
put it about 100 million and nobody argues that there is more than that. E.O. Wilson is in the
biodiversity field and has done work on insect biodiversity in particular but he exaggerates a
little. Never before in history have there been that many species alive and this is not surprising.
The ongoing forces to diversify would have to bring about larger and larger diversity of species.
It is not a continual process. When life first took root on the planet went from Ediacaran from
multi-cellular life divergence followed by a bigger explosion in the Cambrian (Darwin wrote
about this). Bacteria organisms have been around much longer from Achaean period which is
under debate (roughly 3.5 billion years old). There are other fossils now from S. Africa,
Greenland, and Canada but we are pretty sure that 2.5 billion years ago there was life. From that
stretch of time onwards the diversity of life has increased. It of course has not been continuous
there have been bursts of species disappearances. There have been 5 mass extinction events that
are well documented in fossil beds. They all happened after the blue line (signifies about the
Cambrian explosion (600 million years ago) and that is the beginning of multi-cellular life. The
Burgess Shale’s in the Rocky Mountains come from this time (505 to 530 million years old).
The Ediacaran life forms were in the oceans and were animals and they didn’t predate on each
other. They absorbed nutrients from the environment. Before Cambrian life there was at least 1
other major life extinction that brought these life forms to their knees. It is now the tooth and
claw. Prior to the Ediacaran there were extinctions during that time as well but they are poorly
documented, microbes are difficult to pin down in beds. They decompose and maybe leave a
footprint behind.
These disappearances prior to the Ediacaran did experience several massive climate change
episodes throughout the planet that much have brought the organisms to their knees. A time
period that was fairly lengthy. It was known asSnowball Earth’. This concept is fairly recent
and came into our consciousness when you were in high school. It was almost as long as the
reign of the dinosaurs and many believe most of the planet was covered in ice. The last major
ice age ended 10,000 years ago and peaked at around 18,000 and 15,000 years ago. That was the
last major ice age in these parts of the world and Toronto was covered by 1.6 km of ice and near
Hudsons Bay it could have been about 3 km deep. This was when humans were already in this
part of the world. Snowball Earth was 790 to 630 million years ago. Most experts believe that
the majority if not all was covered just like Toronto at the peak of the last ice age.
An ice age as long as 160 million years or so that life forms that existed in the tropics for
example would have been brought to their knees and also unicellular life forms. All adapted to
reasonable climate conditions. There is no question that a majority of life has been brought to its
knees and certainly during Snowball Earth. Life after earth melted in parts of the world
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rebounded and was never completely vanquished. None of the extinctions eliminated life on the
planet and this is important to point out now when people try to convince you that life is going
extinct on the planet. That is not going to happen and it never will.
The largest extinction was here in the Permian-Triassic period. This period ended roughly
around 251 million years ago and it ended with a bang. Not a bang that happened in a few
seconds or days but in bursts that took several million years. (Picture) This was a pig-like
animal and it was the most abundant animal when this extinction was just around the corner.
You wouldn’t have found many dinosaurs because they begin after the Permian-Triassic period
was over. The Mesozoic was the dinosaur time. The big bang event (KT boundary) is the event
of mass distinction but this one was larger. It made room for the dinosaurs but prior there were
things that were more mammal-like (therapsus?). This was similar to modern day mammals than
most dinosaurs. In the end they didn’t last. Mammals had to wait many more millions of years
to take over in terms of dominance on the planet.
This is a fossil that shows how complex multi-cellular life was (picture). This is a sea lily but it
wasn’t a plant. It would belong to the econodermata. This is what Robert Payne studied and is
related to the massive sea stars. The oceanic life was most interesting. We had the pigs running
around on land but in the ocean we had body shapes and sizes that would blow you away! 96%
of all marine dwelling species vanished during the Permian-Triassic and on land around 70%
disappeared. In the ocean they believe there was a major event basically like the black smokers
today that emitted toxic gasses (methane, carbon dioxide, and hydrogen sulphide). The theory
said that when the continents started to move it was a mass release of hydrogen sulphide in the
ocean. Methane can kill very quickly and it smells like rotten eggs. The theory says that this
emission was gigantic (251 million years ago). The other theory is around methane gas and then
another around carbon dioxide. Whichever gas you believe in poisoned oceanic life and this
impacts what goes on on land as well.
Pangaea: (200 x 106 yrs ago). All major land masses were joined together. Every major land
mass huddled next to each other and there were no separate continents that centered on/around
the equator. Life forms on land had a chance to travel around the entire land mass at the time.
The pig was everywhere throughout Pangaea. No doubt the populations would have been
different in each location but they were the same species. Also because it was close to the
equator a vast majority of Pangaea was a tropical or sub-tropical climate.
The supercontinents split up and major rattling in the earth’s crust occurred and this could have
caused the release of the gasses. They built up enough and cracked open violently. We still have
formations that go through Africa that go back to this time i.e. Lake Victoria. It didn’t just
separate but it split in the middle and the process is still ongoing today. These continental land
masses still progress away from each other and it began when the Pangaea broke up. There
comes a point where they must collide on the other side of the world and there will be crumple
zones and mountains. The tallest mountain chain on earth is a good example i.e. Himalayans.
They are still rising because India is still pushing into the continent. If you memorize the height
of Mount Everest you will have to keep changing it year to year as it is still rising. As far as
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Canada is concerned we had the Grenville Mountains and they were the tallest during this time.
They were formed during this time but they have eroded to the ground. It was very tropical as
well so there would not have been snow on the mountains.
In addition and combined with the 1st was the formation of glaciers and their melting. This is
how extensive the ice coverage was seen from the North Pole and now we are down to this. You
see this on the news all the time. I have to chuckle when I hear this because this process of
breaking away and melting at the edges has been ongoing since the Wisconsin Ice Age. At that
time all of Canada was under ice and since then it melted away. If Al Gore was around then he
would have been very alarmed at the speed that the glaciers were disappearing. What is going on
in manmade CO2 is more serious because it happens so quickly and I will show you how quickly
The composition of biomes is also different. This shows what the composition was when the ice
age prevailed. There was a large diversity of eco system types on the planet. Don’t think of the
last ice age as ‘Snowball Earth’. The vast majority of the planet was thriving and there were
rainforest, temperate grasslands, etc. In N. America a large part was ice free. The Laurentide ice
sheet went right over to Greenland and the Cordilleran ice sheet covered the Rocky Mountains.
The Rocky Mountains are around 80 million years old which isn’t that old. The rise of the
Rockies and extinction of the dinosaurs is why on the eastern flank of the mountains we have
beautiful fossil finds of dinosaur skeletons that used to live in those days. Snowball Earth is
different in how long it lasted and its extent. Life persisted and after the snowball melted it
rebounded and from a geological perspective such a major deep freeze could find its ending and
it couldn’t have lasted. The tilt of earth at that time was very different about 60 degrees and
today it is 23.5 degrees. Those are the 2 major ice sheets but notice how they are not going that
far down south. Where they were they had a major influence on the other climates of N.
America. Florida would not have been the place to go to for a semi-tropical vacation as it
snowed a lot. After the ice age and it began to retreat (10,000 years ago) species started to
migrate north. Why did species retract so far south? The climate was pushing a lot further
Continental glacier the peak about 11,500 BP. There was actually a connection between
South America, Middle America, and North America up to Alaska. Alaska was one of the few
areas that were ice free almost entirely during the last ice age. How could that be? It was like
the Mongolian dessert and there was not enough moisture there to have ice. The wind patterns
were changed and there was a major vortex on top of the 2 ice sheets that sucked in moisture.
We have the Arctic and Antarctic now that sucks in things like moisture and also pollutants
(CFCs) and that is why over the Antarctic we have a larger depletion of the ozone layer than
anywhere else. Once enough ice was over top of Canada and parts of the U.S. it developed a
vortex and sucked in the moisture around it at the time and left Alaska bone dry. Parts of
Vancouver and Queen Charlotte Islands were left dry as well. There were parts along the fringes
along the east coast that were not ice covered either because of the vortex. Where the coast lines
are now are not the same as they were then because so much moisture was drawn on the ice the
oceanic levels were lower.
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