Dinosaur Extinction

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Dinosaur Extinction
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Dinosaurs became extinct at the end of the
Cretaceous Period. Experts disagree about what
caused their extinction. Some believe THEORIES
that say extinction happened very quickly, and
others believe a gradual process was responsible.
The extinction event that killed the dinosaurs
affected the entire earth! Some plants and
animals on land and in water became extinct.
Other plant and animals groups did not become
extinct. Fish, turtles, crocodilians, birds and
mammals survived. Scientists use the fossil
record to find reasons for all extinctions. Read
some of the theories. What do you think?
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What Happened to the Dinosaurs?
Explore some EXTINCTION theories.
GIANT IMPACT
VOLCANOES
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DISEASE
MAMMALS
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A giant asteroid strikes Earth. Giant waves
sweep over Earth, fires start all over the world
and huge clouds of dust spread into the
atmosphere. Algae in oceans and plants on land
die with no sunlight. Chemicals from the
asteroid poison rivers, lakes and oceans.
Dinosaurs die quickly from fire, storm, poison
and starvation.
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In this theory, dinosaurs did not become extinct
suddenly. Huge volcanoes erupt, cover the land
with lava and fill the air with huge clouds of
dust. The weather changes between unusually hot
and cold. Plants die over long periods of time.
The plant-eaters died, followed by meat-eaters
like T-Rex. By the time the eruptions stopped,
many plants and animals, including dinosaurs,
were gone.
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One theory suggests that disease caused the
dinosaurs to become extinct. Modern reptiles and
amphibians become infected and get diseases. If
animals dont get the right kind of food, they
suffer diseases. Diseases can be spread by
insects. Could diseases like these have caused
the extinction of dinosaurs?
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Mammals eating dinosaurs' eggs has been
suggested as a cause of dinosaur extinction.
Animals that ate one particular dinosaur's eggs
(more than others) may have prevented any eggs
from that species from hatching. The result would
be that that dinosaur would die out. If every egg
of a species was destroyed, there would be no
more dinosaurs of that species.
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Talk about the problems with each theory. After
you have considered all the theories, decide
which one you think is most likely. Record the
theory on your paper with a picture. Give
reasons for your decision.
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