Transcript Origins of Life & Fossil Evidence B2 6.1 & 6.2

Fossils form in different ways
Hard parts of
an organism
get replaced
by other
minerals..
…most
common.
Hard parts
that do not
decay easily
such as teeth
and bones.
Traces of
plants or
animals are
left behind.
Whole
organism
preserved
in ice.
http://www.classzone.com/books/earth_science/terc/content/visualizations/e
s2901/es2901page01.cfm?chapter_no=visualization
Why do some organisms die out
completely?
• Living things themselves can cause the extinction of each other.
• New predators to an environment.
The Brown Tree Snake was
taken from Australia to Guam
after WWII. It caused
extinction of many bird species.
• New diseases (microorganisms).
A highly infectious cancer is
killing many Tasmanian
Devils. Extinction on islands
are common where animals
live closely together. This
disease is spread easily,
attacks and kills them quickly.
• Competition between species and mutations that give
one species an advantage over another.
24 European rabbits were
released into the wild in
Australia by an Englishman,
Thomas Austin.
They bred so fast and ate so
much that they quickly took
over. Native animals died out
quickly.
Summary
• New predators
• New diseases
• Competition or mutations that give an
advantage to one species over another.
• Remember many other things can cause
CHANGES… a current problem is CLIMATE CHANGE
North Uist
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Hedgehogs introduced
to solve the problem of
slugs.
Hedgehogs bred
rapidly.
They began eating
eggs and chicks of rare
sea birds.
Who will become
extinct?
EXAM TIP! If you give
a reason for an
extinction… tell the
examiner what
change caused it!
Why are fossils useful?
They give us information and evidence
about organisms that lived millions of years
ago.
• Most scientists now believe the Earth is 3
to 4 billion years old.
• Incomplete fossil record is a problem.
• Rocks are constantly melting and moving.
• Have we found all the fossils out there?
Some evidence…
• Fossil records of the horse is good evidence for how this
animal has changed over 55 million years.
• Eohippus had 4 toes and lived on swampy
ground 55 million years ago!
Problems with the fossil record.
• Incomplete record.
• Not enough fossils to show intermediate
species existed.
• Soft bodied organisms.
• Rock cycle.
A wonderfully celebrated
fossil!
Archaeopteryx
Thought to have lived 150 million
years ago
Unearthed 1860/1 in Germany.
Other specimens have since been
found.