The document outlines various theories regarding the extinction of dinosaurs, including asteroid strikes, gradual declines due to climate change, disease, and volcanic activity. It presents evidence supporting each theory, highlighting factors such as habitat destruction, changes in reproductive dynamics, and competition with mammals. Additionally, it discusses the possibility of combined events leading to extinction and the concept of evolution rather than extinction for some dinosaur species.

1. • You are going to be
given a set of cards
with the following
theories on them.
Your task is to arrange
the theories in order of
the most likely cause for
the extinction of
dinosaurs to the least
likely reason.
What Killed the
Dinosaurs?

2. Asteroid Strike.
Scientists believe an Asteroid struck
the Earth and killed the dinosaurs.
Evidence:
Palaeontologists Luis and Walter Alvarez
discovered an unusual layer of clay far
below the Earth’s surface in Italy.
The layer contained Iridium (a rare element) and traces of soot. Iridium is
usually found in outer space and makes up ‘cosmic dust’. Alvarez senior said this
proved an asteroid had struck as the soot was a sign of the huge global fires that
would have resulted.
The size of the asteroid would have produced a lot of energy on impact which
would have killed dinosaurs instantly, any dinosaurs that had survived the impact
would have died from starvation shortly after due to the loss of vegetation
caused by huge global fires. The fires would have posed a problem for dinosaurs
as they would have destroyed their habitats and their food sources.

3. The Palaeocene
Theory.
This theory supports the idea of a
gradual decline in dinosaur numbers
rather than a mass extinction.
Evidence:
The San Juan Basin in the west of America offers evidence for the idea that not
all dinosaurs died at the same time. During a dig in 2001 palaeontologists found
skeletal remains of three species of dinosaur whose bones were believed to have
shown that non-bird species had relocated to other areas of the world (possibly
after a catastrophic event) and continued to live there for many years.
The bone fragments showed no signs of wear and tear, scratches, dents or other
abrasions and were completely smooth which dismissed ideas that bones had been
transported to the region by water.
Pollen was also found close to the bones, this pollen has already been dated to a
later period than the life span of dinosaurs. This helps the argument that the
dinosaurs died out gradually and were not all made extinct at the same time.

4. Climate Change.
Even the dinosaurs couldn’t escape the
effects of climate change!!
Evidence:
Scientists believe that the climate and
atmosphere on Earth has constantly cycled
and changed. Scientists believe the
temperature rose due to excess carbon dioxide in the atmosphere.
This concentration of CO2 would have killed dinosaur embryos, removed much
needed oxygen from the seas so that sea living dinosaurs would have died too. The
increase in temperature would have been caused by the growth of algae due to
CO2 levels.
Dinosaur’s gender was decided on by the temperature during incubation and with
the increase of temperature due to a change in climate, more female dinosaurs
would have been born therefore gradually reducing the population sizes and
decreasing the rate of reproduction between a species.

5. Disease.
A theory to suggest that several ways of
viruses and new diseases appearing or being
spread by the migration of species.
Evidence:
Epidemics of new disease were enough to wipe
out the dinosaur, a lot like mutations in
microbes today these were too powerful for the immune systems to handle.
These diseases may have been the result of bacterial and viral evolution, due to
migration of different species of animal who were carriers of a particular illness.
Scientists also believe that disease may have wiped out vegetation meaning whole
food chains were affected, if plants and trees were no longer available to
herbivores they would begin to starve and as a result so would carnivorous
dinosaurs who fed on them.
With the immune systems unable to adapt quickly enough to combat these
microbes, the dinosaurs would have been wiped out by something a lot smaller
than itself.

6. Gravitational
Change.
Dinosaurs were killed off by the consequences of
Gravity changing on Earth.
Evidence:
The size of gravity changed possibly due to a change
In the orbit of Earth. The change in gravity is similar to the change in energy
needed by electrons to move to another energy level. This change in gravity
meant that dinosaurs were now to heavy to hunt, move and ultimately live.
This change in gravity did not affect other life forms such as birds and
reptiles because they had already undergone evolutionary changes. Birds are
‘designed’ to fly. The change in value for gravity meant that water became
denser and heavier causing pressure changes in the seas. Sharks, fish and
other life who were used to living in deeper areas of the seas were not
affected by this change but it meant they could live in other locations too.

7. Continental Drift.
The effects of the continent Pangaea
splitting were disastrous for dinosaurs.
Evidence:
Pangaea was once a supercontinent that has
split to become the different ones we have
today. The movement of the Earths plates
caused tidal changes, it caused the currents
to change direction and led to rises in sea level in certain areas of the world. These
changes meant whole ecosystems changed and food became scarce. At this
time there was flooding of many areas too, evidence for this floods include
clams and fish fossils being found in mountains and in areas where you would
not expect to find them. Scientists believe they have been found there as a
result of being transported by water and then squashed in sedimentary rocks
that have also been ‘washed up’.

8. Combined Events.
A general theory that suggests more
than one factor caused the dinosaurs to
be extinct.
Evidence:
Fossil records and carbon dating of bones
found all point to the fact that different
species of dinosaur lived at
different times. This favours the idea that several different factors affected
the lives and ultimately the demise of the dinosaurs.
The theory takes into account differences in climate that would force species to
die out as they wouldn’t be able to adapt quick enough to survive in new conditions.
It also allows for factors such as new diseases, less food, volcanic eruptions and
orbital changes to be taken into account.
The combined theory also gives weighting to the Palaeocene Theory.

9. Evolution.
Evolution not extinction!!
Evidence:
Many scientists believe that
many of the dinosaurs simply
evolved into many of the modern animals we have today
rather than becoming extinct.
If you look at the characteristics and anatomy of many
reptiles and lizards, you can see similarities between
prehistoric creatures and these modern day animals.
Looking at the skeletons, bone fragments and fossils of flying dinosaurs and
comparing these with the birds of today there are many structural similarities,
the shape of the beak the joints of the wings etc.
These pieces of evidence back up the arguments that many species of dinosaur
simply moved with the times and adapted!

10. Volcanic Activity.
Eruptions from volcanoes caused
massive atmospheric changes.
Evidence:
Volcanic eruptions caused molten rock
to flow through giant cracks in the
ground in
an area called the Deccan Traps (this
is now India). Land became covered in
layers of lava, destroying habitats and killing life.
Huge clouds of dust, sulphuric acid droplets, and noxious gases from the
eruptions filled the air with poisonous fumes suffocating many life forms. As a
result, the world's weather changed rapidly and the climate continued to be
unpredictable for many years.
Fossils found in the area help to back up this theory as they show evidence of
cooling and soil from the location shows traces of soot. The huge clouds also
meant the sun was blocked this meant vegetation died which would have a huge
impact on food chains at the time.

11. Out competed
and
non-adapting.
Survival of the fittest!
Evidence:
One theory is that at the time of the dinosaurs there were many mammals and
birds living alongside them. The theory suggests that due to atmospheric or
climatic changes dinosaurs were out competed by animals that had furry coats
to keep them warm, they also suggest that herbivores began to outcompete noncarnivorous dinosaurs for trees and plants.
Other ideas include dinosaurs being out competed for territory and eventually
caused a decline in many of the species of dinosaur.