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25 Evolution
E 25.1 Is there evidence for the theory of evolution?
(Book 3, p.254)
(1)
Evolution
(演化)
is the process by which new organisms develop from pre-existing
organisms over a long period of time.
 Evolution of organisms (only some main types are shown)
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Formation of fossil (Book 3, p.254)
(1)
Fossils
(化石)
are the preserved remains or traces of organisms from the past.
mud and sand
from river
1
The (2)
skeleton
of a fish is
buried by the mud and sand on the
fish skeleton
bottom of a lake.
bottom of
a lake
more recent
mud and sand
2
After millions of years, the mud and
sand become (3)
fish skeleton
becomes fossil
rock
due to great pressure from the upper
rock
layers of mud and sand.
younger rock layer
3
older rock layer
(4)
Earth
movement
raises the rocks above the water.
fossil skeleton exposed
4
Further earth movement or
(5)
weathering
exposes the
fossil skeleton and makes it easier to
find.
 Formation of fossils
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111
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Uses of fossil records (Book 3, p.254)

Fossils are usually preserved in (1)
sedimentary
rocks
(沉積岩)
which
are formed by depositing one layer of mud and sand over the top of another.

The lowest layer contains the (2)
the (3)
latest
earliest
fossils while the highest layer contains
fossils.

A sequence of fossils is called a (4)

Fossil records suggest organisms evolve from (5)
fossil
record
simple
(化石紀錄).
to (6)
complex
life forms over millions of years.
 Shell fossil
 Trilobite (三葉蟲) fossil
 Dinosaur fossil
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Practical 25.1 Examination of fossil records
(Student’s Book 3 p.256; Activity Book 3 p.135)
STS connection 25.1 Extinct organisms (Student’s Book 3 p.257; Activity Book 3 p.138)
Section concept diagram (Student’s Book 3 p.257)
E 25.2 How can evolution be explained? (Book 3, p.260)

The process of evolution can be explained by the theory of (7)
selection

Natural selection is the (8)
(9)

(自然選擇)
elimination
natural
which was proposed by Charles Darwin (達爾文) (18091882).
preservation
of favourable variations and the
of unfavourable variations.
Natural selection allows those organisms with favourable variations to (10)
(‘survival of the fittest’ 適者生存) and (11)
reproduce
survive
. On the other hand, those
individuals with unfavourable variations will compete less well and will be less likely to
breed.
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Darwin illustrated the evolution of the neck of giraffes by his theory of natural selection:
1
In a population of giraffes, some have long necks and some have short necks. When the
(1)
food
supply
is enough, neck length is not important for the
survival of the giraffes.
2
When the weather becomes dry for a long time, no grass grows on the ground.
Short-necked giraffes will die. A (2)
long
neck becomes a favourable
variation for survival. It allows giraffes to get leaves from tree tops.
3
(3)
Long-necked
(4)
offspring
giraffes survive and pass this characteristic on to their
.
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Significance of variation (Book 3, p.261)

Variations provide the (1)

Variations cause some individuals to be better (2)
raw
material
others and reduce the chances of (3)
for evolution.
adapted
extinction
to the environment than
of the entire species when there is a
change in the environment.
An example of natural selection (Book 3, p.261)

The case of (4)
peppered
moths
(斑點蛾)
in England is a good example of
natural selection.

The peppered moths normally have light-coloured body and wings.

After the Industrial Revolution (工業革命), the (5)
mutant
(突變型)
form, which has a
dark-coloured body and wings, has greatly increased in number.

Explanation of the increased occurrence of the mutant form:
1
Before industrialization, the (6)
normal
form
of moths on the light-coloured tree trunks was hard to
see. The mutant moths were easily seen and eaten
by birds.
2
During industrialization, the tree trunks were
(7)
darkened
by the smoke and soot released
from the factories. The normal form became easier for
birds to see and eat. The (8)
mutant
form was
left to survive and reproduce.
3
Therefore, much greater numbers of mutant moths are
present in polluted areas.
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STS connection 25.2 The work of Darwin and Wallace
(Student’s Book 3 p.261; Activity Book 3 p.141)
STS connection 25.3 Misuse of antibiotics and evolution of resistant bacteria
(Student’s Book 3 p.262; Activity Book 3 p.143)
Quick check (Student’s Book 3 p.262)
Section concept diagram (Student’s Book 3 p.263)
Review (Student’s Book 3 p.263)
Summary concept diagram (Student’s Book 3 p.264)
Note:
Misuse of antibiotics often leads to evolution of resistance in bacteria. Whenever bacteria are exposed to an antibiotic,
only the resistant forms are selected to survive and reproduce. Therefore, the offspring become resistant to that type of
antibiotic and may cause deadly diseases. To limit the evolution of antibiotic-resistant bacteria, the use of antibiotics
should be reduced and the treatment course must be completed when one is taking antibiotics.
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 Practice question
There are two varieties of moths, light form and dark form. The light form has light-coloured wings
whereas the dark form has dark-coloured wings. After marking the undersides of the wings of a
number of each variety with a spot of paint, a biologist released the marked moths to a forest
polluted by smoke and soot, and an unpolluted forest. The table below shows the percentage of
marked moths caught in the two forests after a few days.
Variety
Percentage of marked moths caught
Polluted forest
Unpolluted forest
Light form
13%
13.7%
Dark form
27.5%
4.7%
E a
The light form and the dark form belong to the same species of moths. Explain one genetic
cause that may lead to this variation in their wing colour.
(2 marks)
Random fertilization (1m). The random fertilization of gametes, each having a different
genetic make-up, produces different combinations of alleles, leading to variation (1m).
E b
Why were the undersides of the wings marked, but not the upper sides?
(1 mark)
To keep the camouflage provided by the wings (1m).
E c
In both forests, only a small percentage of marked moths were caught. Suggest one reason
for this.
(1 mark)
Moved to other areas / eaten by predators. (1m)
E d
i
Which of the varieties of moths could survive better in the polluted forest and the
unpolluted forest respectively?
(2 marks)
Dark form and light form respectively (2m).
ii
Explain the difference in d i in relation to predation by insect-eating birds.
(4 marks)
In the polluted forest, the tree trunks are darkened by the pollutants (1m). Light
form becomes easier for birds to see and eat while the dark form are able to
survive and reproduce (1m). In the unpolluted forest, the tree trunks are
light-coloured (1m). The dark form becomes easier for birds to see and eat while
the light form can survive and reproduce (1m).
Total: 10 marks
－ END －
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