Transcript Cyclicity in Extinction

Cyclic extinctions
in the fossil record
Alex Cook
Thoughts
 Evolutionary progression seems to be clearly
demonstrated in that certain kinds of creatures in the
upper layers of the fossil record are rarely if ever seen
in lower layers. Many layers also show specialized
environments. Some layers contain mostly fish and
invertebrate fossils while other layers show animals
indicative of land. Since each of these layers seems so
specialized it is easy to conclude that one type of
creature gave rise to the next type of creature over the
course of whatever time that it took to form the various
layers between them
Reasons for extinction
 The most common reason we see that a
species go extinct is the Darwinian
thought that they could not cope with
their surroundings, but actually
paleontologists do not know real reasons
for thousands of extinction events in the
fossil record whether they were large or
small events.
Types of cyclic extinction
 Raup and Sepkoski’s study of marine
invertebrates over the last 600 million
years found that 2 to 5 families
disappeared each million years,
background extinctions.
 They also found that 5 intervals in that
time period where 10 to 20 families
became extinct, these were called “mass
extinctions.”
The “Red Queen” theory
 Species must consistently improve to
avoid extinction.
 They must compete for resources while
natural selection is constantly changing
species to keep up.
 “You must keep running and running to
stay in the same place.” (Alice through
the looking glass)
Asteroid Impact
 This very popular theory says that
extinctions are due to large asteroids
hitting the earth and causing immense
climate change due to tidal waves, and
blackouts associated with debris from the
impact.
Tectonic activity
 Another theory put forth by
paleontologists is that volcanoes and
plate tectonics could cause extinctions,
this would be done by again coating the
earth in ash and blowing thousands of
tons of ash into the atmosphere causing
a dark earth, which leads to a cold earth.
This would also hurt photosynthetic
activity in ocean and land plants.
Ice Age
 Still another idea for mass extinctions is
that shift in climate or another process
stated earlier could trigger an ice age,
cooling the planet tremendously, newer
studies show that this type of climate
change can occur very quickly and with
out too much warning. This type of
catastrophe is very real
My ideas
 I would like to propose that the reason for
many background extinctions. The
environment changes due temperature,
or other processes, this makes some
species less suitable to live in the new
surroundings and they die out.
 The mass extinctions, I think are due to
catastrophic events like impacts, tectonic
activity, or ice ages.
Conclusions
 Cyclic extinctions could be caused by
many processes. These events are still
major mysteries in today’s geology,
extinctions are some of the most studied
events in all of geology. With continued
study and research scientists can
hopefully understand these amazing
events.