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The origin of birds has long been debated.
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• The fossil of the earliest known bird,
Archeaopteryx, was discovered in 1861
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Fossils of feathered dinosaurs have been
discovered.
fossil of
Caudipteryx (尾羽龍)
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They provide evidence to support that
birds evolved from
fossil of
dinosaurs.
Caudipteryx (尾羽龍)
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They provide evidence to support that
birds evolved from
reconstructed
dinosaurs.
Caudipteryx
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How did life originate on earth
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Why are there so many different kinds
of organisms on earth today
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What are fossils What is their
importance in the study of evolution
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30.1 The origins of life
How did life originate?
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Theories on the origin of life on
Earth
1. Special creation
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Theories on the origin of life on
Earth
2. Spontaneous generation
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Experiments that disapprove
spontaneous generation of life
Francesco Redi (1626-1697)
•One of the men to dispute
"Spontaneous Generation"
Did experiment with meat and
flies, if flies were prevented
from landing on meat, it did not13
produce maggots
Theories on the origin of life on
Earth
4. Cosmic theory
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Theories on the origin of life on
Earth
3. Primodial soup – chemical evolution
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30.1 The origins of life
Maybe simple organic molecules
were formed from inorganic
substances present in early
earth’s atmosphere by the action
of UV radiation and lightning.
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30.1 The origins of life
The organic molecules then joined
to form the first organism.
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30.1 The origins of life
Let me do an
experiment to test
this hypothesis.
Stanley Miller
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30.1
The origins of life
electric
spark
gas mixture
of H2, H2O,
NH3, CH4
boiling
water
heat
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30.1
The origins of life
simulated
lightning
condenser
boiling
water
heat
gas mixture
of H2, H2O,
NH3, CH4
water out
water in
liquid containing
organic molecules20
30.1
The origins of life
This supports the idea
that organic molecules
can be made from
inorganic substances
under the conditions of
early earth.
Stanley Miller
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30.1
The origins of life
No one knows the exact origins of
life. Scientists believe that the first
organisms are formed by joining
organic molecules together. The
organic molecules are produced
from simple inorganic substances
present in early earth’s atmosphere.
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30.2 Biological Evolution
What is the origin of the
diversified life forms on
earth today?
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Life evolves and our Earth has been changing
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30.2 Evolution
Evolution is defined as
the development of complex
•
organisms from pre-existing simple
organisms over the course of time.
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30.2 Evolution
• scientists generally accept the
theory of evolution (進化論)
- life on earth started from a
common ancestor (共同祖先)
- this ancestor developed into all
the different species today over
a long period of time
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Biological evolution
Biological
evolution focuses
mainly on the
relationship
between species
and major phyla
rather than the
origin of life
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Common ancestor of all living
things
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30.2
Evolution
Evidence for evolution: fossils
• preserved remains or traces of
organisms
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30.2
Evolution
Evidence for evolution: fossils
• most are formed from the hard parts
of organisms
bones
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30.2
Evolution
Evidence for evolution: fossils
• most are formed from the hard parts
of organisms
bones
shells
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30.2
Evolution
Evidence for evolution: fossils
• most are formed from the hard parts
of organisms
bones
shells
teeth
wood of trees
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30.2
Evolution
Evidence for evolution: fossils
• eggs, footprints, dung and pollen can
also become fossils
dinosaur egg fossil
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30.2
Evolution
Evidence for evolution: fossils
• eggs, footprints, dung and pollen can
also become fossils
dinosaur footprint
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30.2
Evolution
Evidence for evolution: fossils
• eggs, footprints, dung and pollen can
also become fossils
dung fossil
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30.2
Evolution
Formation of fossils
mud and sand
fish
skeleton
bottom of a lake
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30.2
Evolution
Formation of fossils
upper
layer
mud and sand
of sediment
great pressure
fish
skeleton
bottom of a lake
mud and sand become rock
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30.2
Evolution
Formation of fossils
deposition of
mineral salts
mud and sand become rock
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30.2
Evolution
Formation of fossils
skeleton
becomes fossil
mud and sand become rock
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30.2
Evolution
Formation of fossils
skeleton
becomes fossil
mud and sand become rock
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30.2
Evolution
Formation of fossils
rocks rise
above water
younger rock layer
older rock layer
earth movement
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30.2
Evolution
Formation of fossils
younger rock layer
older rock layer
further earth movement or weathering
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30.2
Evolution
Formation of fossils
Video
fossil exposed
further earth movement or weathering
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30.2
Evolution
Fossil record
• fossils are
usually
preserved in
sedimentary
rocks (沉積
岩)
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30.2
Evolution
Fossil record
• fossils are usually preserved in
sedimentary rocks (沉積岩)
uppermost
layer
lowest
layer
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30.2
Evolution
Fossil record
• fossils are usually preserved in
sedimentary rocks (沉積岩)
youngest
rock
most recent
fossil
oldest
rock
earliest
fossil
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30.2
Evolution
Fossil record
• a sequence of fossils
• from it, the evolutionary history can
be traced
• shows a developmental change from
simple prokaryotic organisms to
complex eukaryotic organisms
agree with modern classification system
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30.2
Evolution
Fungi
Animalia
Plantae
eukaryotes
Protista
prokaryotes Archaebacteria
Eubacteria
common ancestor
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30.2
Evolution
Fossil record
• estimate age of fossils by radioisotope
dating (放射性同位素定年法)
 time of existence of organisms
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30.2
Evolution
Fossil record
• first appearance of different groups of
organisms:
land
plants
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humans
reptiles mammals
birds
420
440
350
250
200
fish amphibians
dinosaurs
0.2
time (million
of years ago)
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30.2
Evolution
Evolution of horse
60 million
years ago
today
forelimb
0.4 m
1m
1.6 m
body size
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30.2
Evolution
Evolution of horse
• from the comparison of their structures:
horses became larger in size
forelimb
0.4 m
1m
1.6 m
body size
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30.2
Evolution
Evolution of horse
• from the comparison of their structures:
legs became longer
forelimb
0.4 m
1m
1.6 m
body size
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30.2
Evolution
Evolution of horse
• from the comparison of their structures:
number of toes reduced
forelimb
0.4 m
1m
1.6 m
body size
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Reconstruction of the evolution
of horse from fossil record
horses became larger
legs became longer
number of toes reduced
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30.2
Evolution
Limitations of fossil record
• a continuous fossil record is seldom found
 gaps or missing links (缺少的環節)
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30.2
Evolution
Limitations of fossil record
i) Unable to form fossils
• dead bodies may be eaten by other
organisms or may decay
before fossilization occurs
• conditions may not be suitable for
fossilization
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30.2
Evolution
Limitations of fossil record
i) Unable to form fossils
• some organisms may not be fossilized
e.g. soft-bodied organisms
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30.2
Evolution
Limitations of fossil record
ii) Unable to find a complete set of fossils
• some fossils are located in
inaccessible areas
• most fossils are incomplete
and may be damaged
• chance of discovery
is low
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Evidence for evolution:
comparative anatomy
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Evidence for evolution:
comparative anatomy – vestigial structure
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Pelvis and hind limb bones in whale
cormorant
Erector muscle in human skin
Flightless cormorant
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Evidence for evolution:
artificial selection
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• Artificial selection has produced dramatic
change in domesticated species
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Evidence
for
evolution:
comparing key
proteins
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30.2
Evolution
Evidence for evolution:
genetic similarities
• body characteristics are determined by
the base sequence of DNA
G A C G T A A G C G
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30.2
Evolution
Evidence for evolution:
genetic similarities
• organisms with closer evolutionary
relationship would have accumulated
less genetic differences
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30.2
Evolution
Evidence for evolution:
genetic similarities
• the more similar the base sequence,
the closer the evolutionary relationship
98%
85%
similarity in base sequence
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Homology of molecules
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30.2
Evolution
Evidence for evolution:
genetic similarities
• the more similar the base sequence,
the closer the evolutionary relationship
more closely related
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1
How did life originate on earth?
The origins of life is still unknown
today. It is generally believed that
organic molecules were first formed
from simple inorganic substances
present in early earth’s atmosphere.
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1
How did life originate on earth?
The organic molecules then joined to
form the first organisms.
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2
Why are there so many different kinds
of organisms on earth today?
Most biologists believe that the
different kinds of organisms on earth
today evolved from a common ancestor
over a long period of time.
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3
What are fossils? What is their
importance in the study of evolution?
Fossils are the preserved remains or
traces of organisms. They provide
evidence for evolution.
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Evolution
can explain
diversified
life forms
come from a
common
ancestor
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Evolution
supported by
evidence like
genetic
similarities
fossil
record
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fossil record
found in
sedimentary
rock
lower layers
contain
simpler life
forms
upper layers
contain
more complex
life forms
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