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Biology
HSC Course
Stage 6
Blueprint of life
Part 1: Evolution
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Contents
Introduction ............................................................................... 2
Environment and evolution........................................................ 5
Earth’s constantly changing environment ...........................................6
Modelling natural selection ..................................................................9
A case study .......................................................................................13
Evidence for evolution ............................................................. 14
Fossils ................................................................................................15
Transitional forms...............................................................................23
Biogeography .....................................................................................25
Comparative anatomy........................................................................29
Comparative embryology ...................................................................30
Biochemistry .......................................................................................32
Other evidence ...................................................................................33
The evolution of evolution ....................................................... 38
Additional resources................................................................ 41
Suggested answers................................................................. 51
Exercises – Part 1 ................................................................... 57
Part 1: Evolution
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Introduction
Popular culture often depicts the process of evolution as a development
of organisms from lower simple forms to higher and more sophisticated
states of organisation. These descriptions often place humans at the top
of the evolutionary ladder. This is a notion as outdated as the Earth
being the centre of the universe.
The famous American evolutionary biologist, Stephen Jay Gould said:
Darwin’s revolution will be completed when we smash the pedestal
of arrogance and own the plain implications of evolution for life’s
non-predictable nondirectionality.
That is, evolution does not necessarily produce more complex and
sophisticated organisms. Rather, it produces different ones.
The evolution of species results from changes in the environment.
Individual members of a species that can survive the pressures of change
have some special features, called adaptations, which enable it to cope
and to reproduce.
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The first part of this unit deals with the nature of these environmental
changes – be they physical, chemical or a result of competition for
scarce resources.
You will be asked to prepare a case study either on the evolution of the
Australian megapods (kangaroos) or the plant Nothofagus, showing how
changes in the Australian environment have led to changes in a species.
Many sciences today describe and explain how present and past species
are related to each other. Evidence that species evolve from a common
ancestor has come from studies such as palaeontology (the study of
fossils), comparative anatomy and embryology.
The sciences of biogeography (the study of the distribution of organisms)
and biochemistry (the study of molecules that make up living matter)
also reinforce what is understood about evolution. This part of the
module will describe, using specific examples, how evolution is
supported by these studies.
To complete an activity in this unit you will need red and green food
colouring, a packet of toothpicks, two small plates, two forks and some
paper towel. Please get them ready before you start this part.
In this part you will have the opportunity to learn to:
•
•
outline the impact on the evolution of plants and animals of:
–
changes in physical conditions in the environment
–
changes in chemical conditions in the environment
–
competition for resources
describe, using specific examples, how the theory of evolution is
supported by the following areas of study:
–
palaeontology, including fossils that have been considered
transitional forms
•
Part 1: Evolution
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biogeography
–
comparative embryology
–
comparative anatomy
–
biochemistry
explain how Darwin/Wallace’s theory of evolution by natural
selection and isolation accounts for divergent evolution and
convergent evolution.
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In this part you will have the opportunity to:
•
plan, choose equipment or resources and perform a first-hand
investigation to model natural selection
•
analyse information from secondary sources to prepare a case study to
show how an environmental change can lead to changes in a species
•
perform a first-hand investigation or gather information from secondary
sources (including photographs/ diagrams/models) to observe, analyse
and compare the structure of a range of vertebrate forelimbs
•
analyse information from secondary sources on the historical
development of theories of evolution and use available evidence to
assess social and political influences on these developments.
Extract from Biology Stage 6 Syllabus © Board of Studies NSW, originally
issued 1999. The most up-to-date version can be found on the Board's website
at http://www.boardofstudies.nsw.edu.au/syllabus_hsc/syllabus2000_lista.html
This version October 2002.
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Environment and
evolution
The fact that species become extinct indicates that its members were not
very successful at coping with changes in their environment. Whether
they were sudden or gradual changes, the fact remains that the members
of the species did not survive the pressures of change and were not able
to thrive and reproduce.
Adaptations to suit environments
Your experiences with nature and living things on Earth have probably
come from reading books, watching television and video, and going out
in the bush or to the beach. You may have had the opportunity to go to
different environments around Australia or even to other parts of the
world. The Preliminary course must have also broadened your ideas
about life on Earth.
Whatever your experiences and observations have been, you would
conclude that living things survive best in the environment that they are
most suited for. What is less obvious is that all living things evolved to
become suited to the environment that they live in. While adaptations
are easily observed and described, the evolution of these adaptive
features is not usually noticed in a human lifetime.
In past times, people thought that species never changed and neither did
the environment. Today we know that the environment is constantly
changing and that species evolve to make the most of conditions in their
background. Species with features most suited to their environment
thrive and live to reproduce.
Environments on Earth are diverse; therefore there is a diverse range of
life on the planet. Some environments change periodically, for example,
seasons. Some environments have regular changes over longer periods
of time. Sometimes environments change gradually over millions of
years; at other times, environments may undergo a sudden
drastic change.
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Whichever way the environment changes, the organisms living there
have pressure put on them to survive. The adaptive features of
individuals give them survival value. Environmental pressure selects
those individuals with the greatest survival value.
Using the information you have just read, write a paragraph to state the link
between the environment and evolution of organisms.
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
Check your answer.
Earth’s constantly changing
environment
Changes to the environment can be grouped into one of the following:
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•
changes in physical conditions
These include any non-living natural conditions such as wind,
temperature and availability of water. Some changes in physical
conditions can occur suddenly or annually.
•
changes in chemical conditions
The concentration of chemicals in the environment that an organism
uses or is adapted to may change. For example, the salt
concentration (salinity) in soil or in water might increase.
•
competition for resources
Changes to the amount of resources available affects the struggle for
survival among the species and within the species. Situations such
as the introduction of a successful competitor change the dynamics
in a community, often causing a strain on resources.
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Think about all the possible changes that can happen in an environment.
For example, the climate may become warmer or a new species may be
introduced into an area.
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List as many features in the environment that you can think of that
change over a period of time.
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
2
Now group these changes into physical, chemical and ones caused
by changes to competition. List these in the table below.
Physical
Part 1: Evolution
Chemical
Changes to competition
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3
A number of scenarios to do with environmental change are listed
below. Describe an adaptive feature of an animal and/or a plant that
will help it to survive the change.
a) An area dries out because of climatic changes.
__________________________________________________
__________________________________________________
__________________________________________________
b) A new species of frog moves in, reproducing and spreading
rapidly. It is poisonous to the predators of the new area.
__________________________________________________
__________________________________________________
__________________________________________________
c) The salinity (amount of salt) of the soil of an area slowly
increases.
__________________________________________________
__________________________________________________
__________________________________________________
Check all your answers.
Most biologists today agree that major evolutionary changes have been
associated with dramatic changes to the Earth’s environment. These
changes have mostly been brought about by the drifting continents,
causing ocean currents to change as well as affecting volcanic activity
and mountain building.
More recently, scientists have shown direct links between mass
extinctions (where most species on Earth become extinct over a short
period of time) and collisions with extraterrestrial objects such as comets
and meteoroids.
Do Exercise 1.1 now.
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Modelling natural selection
In the module called Evolution of Australian biota, you learnt that
changes in a population are due to selection pressures. Perhaps the best
example of this is the classic study of the peppered moth.
An example of natural selection
This is a historically interesting example of natural selection. The
original experiment has been criticised because there is some doubt as to
whether the moths are found on tree trunks. The moths are usually found
under leaves and branches. Further discredit has come because the
original published photographs of the moths were achieved by gluing the
moths to the trunk of a tree. However it still serves as an example of
how natural selection may occur.
There are two forms (light and dark) of the moth occurring naturally in
the population. In industrial areas the trees were blackened by soot from
the factory chimneys. When the dark moths rested on tree trunks during
the day, they were less obvious to the birds that fed on them, while the
light variation was easily seen and more often taken by these predators.
In these areas, light coloured moths became less and less common.
In the non-industrial areas the opposite was the case – the light coloured
variation was harder to see against the light backgrounds of the trees so
fewer were taken by predators. These were then able to reproduce and
form the next generation. It was the dark coloured moths that
disappeared.
The light variation is easily seen on the dark background and the dark variation
is easily seen on the light background.
Biologists attempt to explain the evolution of camouflage by using the
principles of natural selection. If individuals of a population are obvious
to their natural predators, then their numbers would be fewer than those
that blend into their environment.
Part 1: Evolution
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An open-ended investigation of natural selection
In this experiment you are going to model natural selection by observing
which colours are most easily selected against different backgrounds.
Plan and perform your own activity if you can, or follow the instructions
provided on the following pages.
Aim
To demonstrate the process of natural selection
Equipment
You will need:
•
small bottles of red and green food colouring from the supermarket
•
a packet of about 100–200 toothpicks
•
two small plates and two forks
•
paper towel.
Method–preparation
1
Place 50 toothpicks in each plate. Colour one plate red and the other
green by pouring enough food colouring over the toothpicks so that
they are immersed in the colouring liquid.
fork
toothpicks
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plate
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Leave the toothpicks in the liquid for at least half an hour. Make
sure the toothpicks are stained all over by stirring them around with
the fork.
3
Using the fork, scrape the toothpicks out of the plate and onto some
paper towels to dry.
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Once they are dry you should have a bunch of 100
toothpicks – 50 red, 50 green.
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Shuffle these around in your hand so that they are randomly mixed.
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Now you are going to model natural selection by observing which
colours are selected against different backgrounds.
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You should choose either a member of your family or a friend to act
as the predator. You will do if you are unable to get anyone else.
The toothpicks act as the prey and the background colour will be the
environment.
Steps
1
Sprinkle the random bunch of toothpicks over an area of green
surface, such as a lawn or a green blanket.
2
Get the predator to stand about 5 metres away. When you signal, the
predator must run up to the area and randomly pick 10 toothpicks in
less than 10 seconds. The predator then runs back, puts down what
has been collected, and runs back to do it again. In total, the predator
picks up five bunches of 10 toothpicks (50 toothpicks all together).
3
Sort the toothpicks using their colour, count them and record the
information in the table below.
4
Do at least 5 trials.
5
Repeat the entire experiment on a neutral coloured background such
as a concrete surface or wooden floor. Record these results in the
table below.
Results
Record your results in the table on the following page.
Part 1: Evolution
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On green background
Trial
Red
Green
On neutral background
Red
Green
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2
3
4
5
Average
Write a statement comparing the results for the green background and the
neutral background.
_________________________________________________________
_________________________________________________________
_________________________________________________________
Conclusion
You must account for the difference between the results obtained with
the green background compared with the neutral background. Answer
the following questions.
1
Predict the results you would obtain if the experiment were repeated
on a reddish pink background.
______________________________________________________
______________________________________________________
______________________________________________________
2
Assume that the predator is always present in this environment.
If the toothpicks were able to breed, what could be the most frequent
colour found in a few generations when:
a) the background is reddish-pink
__________________________________________________
__________________________________________________
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b) the background is green.
_________________________________________________
_________________________________________________
3
Write an explanation for selection by camouflage.
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
Do Exercise 1.2 now.
A case study
Your task in this case study is to show how changes in physical or
chemical conditions or increased competition for resources have led to
changes in an Australian species.
Use resources such as the Internet and books, as well as the information
given in the Additional resources section of this part.
Here are two possible case studies that you may choose for this activity.
Case study 1: The evolution of kangaroos
Australia has undergone changes in its climate over time. The kangaroo
is a good example of a species that has evolved over a long period of
time in response to these climatic changes.
Case study 2: The distribution of the Southern Antarctic beech
This tree had a wide distribution in previous times. Now it is restricted
to small pockets in rainforests.
Prepare a short case study and present your report in Exercise 1.3.
Part 1: Evolution
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Evidence for evolution
For any real links between changes in the environment and the evolution
of life, scientists have to make observations that span many millions of
years. This can only be done by indirect methods.
Since Charles Darwin’s book, On the origin of species, was first
published in 18 9, overwhelming support for evolution has came from all
areas of science.
The science of palaeontology (the study of fossils) has provided evidence
for the evolution and history of life on Earth. Palaeontologists have been
documenting details of past life forms (the fossil records) and working
out when they existed and how they may have evolved.
The science of anatomy shows similarities between closely related
species by describing features of their body structure that they have in
common. Comparisons between the embryos of related species is further
support for the idea that species have common ancestors.
Advances in technology, especially in biochemical and DNA analysis,
have given biochemists the best tools yet to accurately describe the
relationships between species. This further supports the theory of
evolution.
In summary, evidence for evolution comes from:
•
palaeontology
•
biogeography
•
comparative anatomy
•
comparative embryology
•
biochemistry.
You will investigate some of this evidence in more detail on the
following pages.
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Fossils
A palaeontologist is a scientist who studies fossils. Since the movie,
Jurassic Park, palaeontology has become very glamorous but in reality
only a few scientists get to study exciting dinosaur fossils.
Reconstructed Tyrannosaurus Rex skeleton at the American Museum of
Natural History, New York (Photo: R Caddy)
Most palaeontologists are busy trying to fill in missing details of the life
histories of less spectacular organisms.
Fossilised worm burrows (Photo: T Reid)
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The fossil records have revealed a few interesting facts about the history
and evolution of life on Earth.
•
All the species of living organisms on the Earth today represent only
a minute number of the species that have ever lived here over the
past three and a half billion years.
•
The species that exist on Earth today have similarities to some of the
pre-existing life forms found in the fossil records.
•
New fossils are constantly being discovered and their clues are
giving scientists a clearer picture of the relationships between past
and present life.
The work of a palaeontologist involves more than hunting for fossils,
digging them out and preparing them for exhibition in museums.
Palaeontologists are also concerned with trying to work out what changes
took place in organisms over geological time, and what relationships the
various fossils bear to one another. This requires careful study of large
numbers of fossils (often mere fragments) and detailed comparisons
between the fossil material available.
Fossilised leaf of an extinct plant called Glossopteris (Photo: M Khun)
Palaeontologists, like most other scientists, usually record both their data
and their comparisons as measurements. Much of this work is done in
the laboratory.
To better understand the information available from fossils, you are
going to study some of the fossil record of a group of organisms – horses.
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The fossil record of horses
Some groups of organisms are very well represented in the fossil record.
One of these groups is the horse family, for which large numbers of
fossils have been found in North America, Europe and Asia. Their
skeletal remains, particularly those of the teeth and toes, have given
important clues to the relationships between them. It has been possible
to suggest the early history of the horse family from this evidence.
Background Information
Horses have their grinding teeth at the back of the mouth, separated from
the front teeth by a toothless space. Their grinding teeth (cheek teeth)
consist of three premolars and three molars on either side of the jaw.
The skeletal characteristic to be used in this exercise is the distance
spanned by the cheek teeth.
span of cheek teeth
premolars
molars
Horse skull showing how the span of cheek teeth is measured.
Optional
This activity is designed to give you an idea about the way that
palaeontologists work out the changes that took place in organisms
over millions of years. (It is adapted from material by H Messel in
Science for High School Students.)
Aim
To infer likely relationships between various horses of the past, using
some of the methods of the palaeontologist
Part 1: Evolution
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Procedure
The span of the cheek teeth has been measured in many fossil specimens
of horses. The data for seventeen of the twenty or so known genera are
presented in the table on the following page.
Genera of equidae
Time of existence
Span of cheek teeth (cm)
1
Early Eocene
4.3
2 Orohippus
Middle Eocene
4.3
3 Epihippus
Late Eocene
4.7
4 Mesohippus
Early Oligocene
7.2
Middle Oligocene
7.3
Late Oligocene
8.4
Early Miocene
8.3
6 Parahippus
Early Miocene
10.0
7 Anchitherium
Early Miocene
11.3
8 Archaeoshippus
Middle Miocene
6.5
9 Merychippus
Middle Miocene
10 2
Late Miocene
12.5
10 Hypohippus
Late Miocene
14.2
11 Megahippus
Early Pliocene
21.5
12 Pliohippus
Early Pliocene
15.5
Middle Pliocene
15.6
Early Pliocene
11.0
Late Pliocene
10.7
14 Calippus
Early Pliocene
9.3
15 Neohipparion
Middle Pliocene
13.1
16 Astrohippus
Middle Pliocene
11.8
Late Pliocene
11.8
Late Pliocene
18.8
Pleistocene
17.6
Hyracotherium
5 Miohippus
13 Nannippus
17 Equus
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Each measurement has been plotted as short bars on the graph grid below.
Beside each bar plotted, write the number from the table of the genus it
represents. The first one is done for you.
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S pa n o f c h e e k t e e t h ( i n c m )
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12
8
1
4
0
Middle
EOCENE
60
Late
Early Middle Late
40
OLIGOCENE
Early
30
Middle
MIOCENE
Late
Early Middle Late
10
PLIOCENE
Millions of years ago
PLEISTOCENE
Early
1 0
Check your answer before proceeding.
How have the spans of cheek teeth changed between genera living at
different times? Find out by following the instructions and answering the
questions that follow.
Start at the oldest genus (Hyracotherium) and work towards the younger
fossils. Draw pencil lines between the bar representing each genus and
the bar representing another younger genus.
Connect the points representing the genera Hyracotherium, Orohippus,
Epihippus, Mesohippus, and Miohippus.
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1
Why can’t you join two or three genera that occurred at the same
time?
______________________________________________________
______________________________________________________
______________________________________________________
______________________________________________________
______________________________________________________
2
Determine what appears to have happened to the span of the cheek
teeth in horses up to late Oligocene times.
______________________________________________________
______________________________________________________
3
Continue the graph by showing the relationship between late
Oligocene and early Miocene genera. The change in span of cheek
teeth can be shown by a single line up to the late Oligocene. What
happens from that time to the early Miocene?
______________________________________________________
______________________________________________________
______________________________________________________
4
What does this suggest about the origin of Parahippus and
Anchitherium?
______________________________________________________
______________________________________________________
5
Working with your pencil, complete the graph to the Pleistocene by
indicating what you consider to be the relationships between the
various genera. What problem are you confronted with?
______________________________________________________
______________________________________________________
______________________________________________________
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6
When you have completed your graph, compare it with the graphs
drawn in the suggested answers. What could you do to help decide
which graph was best?
_____________________________________________________
_____________________________________________________
_____________________________________________________
Since the fossil material is abundant, particularly in western North
America, palaeontologists are able to consider a great many structural
characteristics when working out relationships between these horse-like
animals. The relationships based on any single characteristic like the span
of cheek teeth may conflict with relationships worked out from other
characteristics. The most widely accepted hypothesis of relationships,
based on all available data to date, is shown in the figure following.
Equus
Pliohippus
Calippus
Nannippus
Neohipparion
Merychippus
Astrohippus
Megahippus
Hypohippus
Anchitherium
Parahippus
Miohippus
Archaeohippus
Mesohippus
Epihippus
Orohippus
Hyracatherium
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Are all the relationships proposed by your graph the same as the
relationships proposed in the figure you have just studied? Consider any
similarities or differences then answer the questions below.
Conclusion
7
What was the approximate average change in cheek teeth span per
million years from Hyracotherium to Miohippus?
______________________________________________________
______________________________________________________
8
What was the approximate average change in cheek teeth span per
million years from Miohippus to Equus?
______________________________________________________
______________________________________________________
9
From these results, what generalisation can be made about the rate of
evolution of horses? (This may serve as an indication of the rates of
evolution one might find in other organisms.)
______________________________________________________
______________________________________________________
______________________________________________________
______________________________________________________
______________________________________________________
10 There are countless millions of fossils in sedimentary rocks
throughout the world. Yet the history of life on Earth is still very
incompletely known. List as many reasons as you can why this
is so.
______________________________________________________
______________________________________________________
______________________________________________________
______________________________________________________
______________________________________________________
______________________________________________________
Check all your answers.
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Transitional forms
The example you have just examined of the evolution of the horse is well
studied because there is an abundance of fossil material.
Palaeontologists have been able to describe the relationships between
these fossils because the links between one form and another have been
found. The ancestral tree of 60 million years of horse evolution shows a
gradual development from one genera to the next while giving rise to
other groups.
However most fossil records tracing the ancestors of groups of organisms
are not as complete as the horse. With no fossils showing features
intermediate between two forms that are believed to be linked, scientists
have a hard time explaining natural selection.
You may have seen newspaper headlines like:
Scientists find fossil believed to be the missing link!
These refer to the discovery of human fossils believed to show our
knowledge of human evolution. Intermediate forms or links are called
transitional forms.
Transitional fossils
A transitional fossil is the fossil of a transitional form. A transitional
form, as traditionally used, meant an organism halfway between two
classes or kinds of organisms. Archaeopteryx is often used as an
example of an intermediate form between a reptile and bird.
Archaeopteryx was once believed to be an intermediate form between reptile
and bird.
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However, this view of evolution is outdated. Archaeopteryx is not a
transitional form between reptile and bird. It is both reptile and bird or a
class of its own. (Remember that a classification system is something
invented by humans and imposed on nature.)
One of the problems Darwin had explaining natural selection was the big
difference in features between the classes. Transitional fossils were
supposed to bridge the gap or be the missing link in the fossil record.
Modern biologists explain these differences by saying there is a gap in
the fossil record. As more fossils are found, these gaps will be filled and
the gradual progression of change will be shown.
Why do palaeontologists continue to look for transitional forms in the
fossil record?
_________________________________________________________
_________________________________________________________
_________________________________________________________
Check your answer.
Equilibrium
In 1972, after studying many fossil observations, Eldredge and Gould
claimed that most species appear suddenly and their history shows little
evidence of change. Individual populations might change both
genetically and structurally due to adaptation but overall a species
exhibits a net equilibrium. That is, it tends to stay much the same.
To explain why transitional fossils are not found, Niles Eldredge and
Stephen Jay Gould (1972) came up with the punctuated equilibrium
model of evolution.
Punctuated equilibrium
This view suggests that species originate suddenly whenever rapid
changes in the environment occur. This abrupt appearance of new
species is a random event and is usually associated with a large number
of extinctions called mass extinction.
You will learn more about this concept when you do part 4 of this
module.
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Biogeography
Biogeography (sometimes called zoogeography) is the study of the
distribution of organisms. It is a science that describes where plant and
animal families are found on the Earth today and tries to explain how
they came to be where they are. Biogeography explains these
distributions by bringing together concepts from biology, geology,
palaeontology and chemistry.
The science of biogeography had its beginnings in the early part of the
last century and depends heavily on the work of Charles Darwin and
Alfred Russel Wallace, among others. Notice that these same individuals
were prominent in developing the theory of evolution by
natural selection.
Biogeography as evidence for evolution
Each region has similar species occupying similar niches within its
borders. However, the species are clearly different from those in
adjacent areas.
The boundaries between biogeographic zones are drawn according to the
distribution of vertebrate groups (in particular, families). The regions are
based on the relationships of birds; but the same regional limits work
well enough for fish, amphibians, reptiles and mammals.
There are six biogeographical zones (or provinces), each with distinct
flora and fauna. They are:
•
Palaearctic – North Africa, North Europe and Northern Asia
•
Ethiopian – Africa below the Sahara desert
•
Australian – Australia
•
Nearctic – North America
•
Neotropical – South America
•
Oriental – Southeast Asia and India.
These zones are shown on the map of the world following.
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N
3
3
2
3
Palaearctic
Nearctic
Oriental
Neotropical
Ethiopian
Australian
Biogeographic zones of the world.
Look at the map of biogeographic zones above.
With what physical features of the Earth do the borders coincide?
_________________________________________________________
_________________________________________________________
Check your answer.
Populations that become geographically isolated by means of a barrier
will tend to change. These barriers include seaways, rivers, mountain
ranges, deserts and other hostile environments. They put a wedge
between whole groups of organisms, eventually causing related
organisms – species, genera, families and so on – to diverge.
Wallace’s line
Alfred Russel Wallace, the so-called father of animal geography,
formulated his ideas on evolution by natural selection while observing
and collecting wildlife in the islands of Southeast Asia. He was
particularly impressed by the sudden difference in bird families he
encountered when he sailed some twenty miles east of the island of Bali
and landed on Lombok.
On Bali the birds were clearly related to those of the larger islands of
Java and Sumatra and mainland Malaysia. On Lombok the birds were
clearly related to those of New Guinea and Australia. He marked the
channel between Bali and Lombok as the divide between the Oriental
and Australian biogeographic zones.
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In his honour this dividing line, which extends northward between
Borneo and Sulawesi, is still referred to today as Wallace’s Line.
Philippines
Thailand
South China Sea
M a l a y s i a
Brunei
Pacific Ocean
Sabah
Celebes
Sea
Borneo
Singapore
Halmahera
Papua
New Guinea
Kalimantan
Sumatra
Sulawesi
Irian Jaya
Java Sea
Banda Sea
Java
Flores
Timor
Bali
Lombok
Arafura Sea
Timor Sea
Indian Ocean
0
100 200 300 400 500
Gulf of
Carpentaria
Kms
Wallace’s Line
Australia
Map of South-East Asia showing Wallace’s line.
To the west, the Asian animal community includes such mammals as the
rhinoceros, orangutan, tapir, tiger and elephant. To the east are found
animals related to Australian fauna. They include birds such as
cockatoos, bowerbirds and birds of paradise as well as marsupials such as
bandicoots and cuscus.
The core areas of the Oriental and Australian provinces are clearly
distinct but overlaps exist on the edges of the boarders. Thus some
biogeographers recognise the region of islands between Java and New
Guinea as a mixing zone of Oriental and Australian fauna.
Rather than try to fix where the line between these two realms should lie,
most modern biologists recognise that the whole Indonesian archipelago
region represents a zone of changeover. Within this zone, the two faunas
progressively replace one another.
This changeover zone exists because, as the Asian and Australian
landmasses drifted closer together, organisms were able to move out of
the places where they originated into new territories.
When the world is divided into zones using the distribution of flowering
plant groups, the resulting zones do not coincide with biogeographic zones
based on vertebrates. What factors could account for the differences in the
distribution patterns of vertebrates and flowering plants?
_________________________________________________________
_________________________________________________________
Check your answer.
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Biogeographic distributions
There are three important principles used to determine a biogeographic
zone.
•
Environment cannot account for either similarity or dissimilarity,
since similar environments can harbour entirely different species
groups.
•
Affinity or similarity of groups on the same continent (or sea) is
closer than between continents (or seas).
•
Geographical barriers, such as seas, oceans and mountain chains,
usually divide these different groups. The degree of difference
between families relates to the rate of migration or ability to disperse
across the barriers.
Look back at the world map that shows the biogeographic zones of the
world. Think about the different kinds of plants and animals in each
zone. Think about the different environmental conditions in each zone.
Try to think of some examples to illustrate each of the principles above.
For example, environmental conditions in parts of the Ethiopian zone are
similar to conditions in the Australian zone. Some organisms in these
zones, such as arid area plants, are very similar. However, some
organisms, such as gazelle and kangaroos, are very different. Within the
Australian zone, species of kangaroo and wallaby are much more similar
to each other than they are to organisms in other zones. And notice the
positions of the lines separating zones – oceans separate the Australian
zone from other zones, whereas the Oriental and Palaearctic zones are
separated from each other by the Himalayas.
Six degrees of separation
Remember that the degree of separation is the amount of difference
between similar groups of organisms. Three criteria of mammalian
families and their distribution patterns are used to delineate the six
regions known as biogeographic zones, or provinces. These are:
•
the total number of families
•
the number of families originating from (endemic to) this province.
This is a measure of uniqueness of the mammalian fauna
•
the number and location of other regions with which mammalian
families are shared.
Rank the biogeographic zones by dividing the number of endemic families
by the number of shared families. (Hint: Australia would be first because
it only has eight endemic families and only one shared family.
The calculations have been done in the first row as an example.)
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Biogeographic
zone
Total number of
families
Ethiopian
Number of
endemic families
38
Number of
shared families
12
2
Endemic families
shared families
12
2
Neotropical
32
16
3
Oriental
30
4
3
Palaearctic
28
2
3
Nearctic
24
4
3
9
8
1
Australian
=6
Check your answers.
The comparison of endemic to shared families is used as a measure of
how much biological separation exists between mammals of the
biogeographic zones.
Now complete Exercise 1.4.
Comparative anatomy
Different groups of organisms often have similar structural features.
This observation is also used as evidence that species can evolve from a
common ancestor.
Comparing the mouthparts of insects
The mouthparts of insects are an example of a similar structure modified
for its function. In various insects, the same basic plan has been
functionally modified for biting, piercing, chewing or sucking.
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Vestigial structures
Those structures that functioned in ancestral organisms but are reduced
(in structure and function) in the descendant are called vestigial
structures. Some examples in humans include vertebrae of coccyx
(tailbone) and the appendix on the intestines. In some other mammals,
the appendix is a larger organ with a function in digestion.
Comparing vertebrate forelimbs
The skeletons of vertebrates provide a clear example of structural
similarities. The five fingered limbs (called pentadactyl limbs) of
vertebrates are considered to be similar structures. The hand of a human,
the forefoot of a horse, the flipper of a dolphin and the wing of a bat all
have the five-fingered plan. The same basic plan is modified to serve a
different function for each type of vertebrate.
In your next exercise you will need to observe, analyse and compare the
structure of a range of vertebrate forelimbs. You can do this by looking
at some in a museum, looking them up on the Internet and/or using
information in the diagram in Exercise 1.5.
You will find some helpful starting points on the Science online webpage at:
http://www.lmpc.edu.au/science
Now complete the tasks in Exercise 1.5.
Comparative embryology
Embryology is the study of embryos and their development.
Embryologists have discovered that all vertebrate embryos look alike
during their early development. It is almost impossible to distinguish
between the early embryos of fish, chickens and humans. They become
recognisable later in their development.
The common features of embryo development
found throughout the vertebrate group include:
•
30
gill slits appear even in embryos of fully
terrestrial organisms with no sign of gills
as adults.
•
tail
•
notochord develops into vertebrae in
all vertebrates.
gill slits
notochord
tail
A vertebrate embryo.
(Adapted from Messel, Science for
High School Students)
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Study the following diagram showing the stages of development of four
vertebrate groups and determine which row shows the most similarity.
man
pig
salamander
fowl
Stages of development of four vertebrate groups.
(Adapted from Messel, Science for High School Students)
Check your answer.
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Biochemistry
The building blocks of life are fundamentally the same for all living
things and they use the same basic biological molecules for similar
functions. For example, the amino acid building block molecules are the
same in all known species. Biochemists can analyse the sequence of
amino acids of a protein common to many species, match the similarities
and then compare them with other species.
The table below shows the number of amino acids for a common protein
called cytochrome c that are different in humans and another species.
Species compared
Number of different amino acids
human/chimpanzee
0
human/horse
7
human/snake
11
human/fly
13
human/cauliflower
19
human/yeast
26
1
Based on the similarities between amino acid sequences for
cytochrome c:
a) which species is the most similar to humans? _____________
b) which is the least similar to humans? ____________________
2
What can you infer from this information?
______________________________________________________
______________________________________________________
______________________________________________________
Check your answers.
There are many more techniques used by biochemists and molecular
biologists for showing similarities between species. A good example is
DNA sequencing. These techniques are better explained further on in the
module after you have learnt about DNA and biotechnology in Part 4.
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Other evidence
There are two other ways to organise evidence that are used to support
the theory of evolution. These use observations from the areas you
have already considered (comparative anatomy and so on).
These other ways are:
•
divergent evolution
•
convergent evolution.
Divergent evolution
When a new area, such as an island, appears or something causes an area
to become vacant, colonising organisms move in. Those with features
best suited to the new environment will function more efficiently, thrive
and produce offspring because there will be little competition for
resources. Adaptations make it possible for these colonising organisms
to cope with the new (changed) environmental conditions.
Because organisms in a population are slightly different from each other,
groups within the population will be able to thrive and reproduce best in
different parts of the new environment, so the groups will gradually
become different from each other. Or, different species could become
more alike to better use the same environment. This is divergent radiation.
Divergent radiation commonly occurs immediately following an
evolutionary breakthrough. This means a population with an innovative,
better adapted feature colonises a vacant ecosystem, speciates (forms
species) and radiates to occupy the available space. (Speciation can also
occur in the same environment.)
An example of divergent radiation – dinosaurs and mammals
At the beginning of the Triassic period, some 250 million years ago,
the terrestrial surface of Earth had many environments unoccupied by
vertebrates. The only vertebrates living on land were amphibians
and these were restricted to wet areas close to rivers, lakes and the coast.
1
Why didn’t the amphibians venture inland?
_____________________________________________________
_____________________________________________________
_____________________________________________________
2
Which group of animals would have lived inland?
_____________________________________________________
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By the middle and toward the end of the Triassic period, a variety of
egg-laying vertebrates evolved and diversified to occupy every
environment on Earth, including the seas. They were, of course, the
dinosaurs. They are well documented in books, museums, videos and
movies. Their dominance on the planet was to span the Jurassic period
and last some 200 million years.
3
What feature did dinosaurs possess that enabled them to venture
away from water?
______________________________________________________
______________________________________________________
Mammals evolved during the Triassic period but had to be content with
occupying the nooks and crannies of a planet dominated by dinosaurs.
Fossils of mammals from around these times show them to be small
rat-like creatures with little variation among them. They remained this
way for 100 million years.
A mass extinction event, believed to be due to a collision with an asteroid,
caused the dinosaurs to rapidly disappear from their dominant position.
Only one variety is thought to have survived to become the ancestor of birds.
Around 60 million years ago, with the dinosaurs out of the way, the
mammals began to occupy environments and niches left vacant by their
previous occupants. The fossil record shows a sudden increase in
diversity of mammal forms. Eventually millions of mammals ended up
dominating almost every environment on Earth. Some varieties
occupying the seas and oceans gradually changed to become the whales
and dolphins of today.
4
What factors lead to the sudden increase in mammal’s diversity?
______________________________________________________
______________________________________________________
______________________________________________________
5
Explain what divergent radiation means in your own words.
______________________________________________________
______________________________________________________
______________________________________________________
Check your answers.
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Darwin’s finches
The finches of the Galapagos Islands are examples of many species
evolving from one, to take advantage of the available environments.
Diversity in a species may eventually result in speciation, which is the
creation of new species, when an area or environment has not reached its
potential or been fully colonised. The kind of adaptive radiation that
leads to the evolution of many divergent forms from one species is called
divergent evolution.
It is believed that one species of finch may have arrived on a Galapagos
island and then divergent evolution lead to the many different species of
finch found on the Galapagos Islands today.
Different beak structures in finches found on different islands in the
Galapogas.This illustrates how the species has diverged from the original form .
Charles Darwin explained divergent radiation by using the finches of the
Galapagos Islands as an example. Look up this work in a biology book at
your local library or on the Internet (use the words Galapagos, finches and
Darwin in a search engine). Then complete Exercise 1.6.
Convergent evolution
Today there is a staggering array of life forms on the Earth and each
reflects diverse ways of life. There are probably as many ways of life as
there are species.
Many organisms that have evolved independently now live in very
similar ways. Organisms that live in similar environments have the same
selective pressures applied to them. In the example below there are three
different vertebrates groups, all showing a similar body structure. This is
called convergent evolution.
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35
mammal
reptile
fish
The diagrams above show major vertebrate groups that occupied the seas.
1
What physical features do all these animals have in common?
_____________________________________________________
_____________________________________________________
_____________________________________________________
2
Although each sea creature represents a completely different
vertebrate group, they all look very similar. How would the theory
of natural selection (by Darwin and Wallace) explain what caused
each of these vertebrate groups to have the same body shape?
______________________________________________________
______________________________________________________
______________________________________________________
Check your answers.
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Another example of convergent evolution can be seen in the shape of
wings for flying. The diagram below illustrates this example.
bat
bird
pterosaur
Adaptation to flight is an example of convergent evolution.
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The evolution of evolution
A requirement for this part of the course is that you
assess the social and political influences on the historical development
of theories of evolution.
What does this mean? You can find out by reading the information below
and answering the questions. Then you will have a clearer understanding
of how and why theories of evolution develop.
Introducing the idea of evolution
It is one thing to discover and explain the workings of nature but the rest
of society has to understand and accept it. Developing an understanding
of how species evolve has been one of the greatest human intellectual
endeavours throughout history.
This long journey of discovery took humans from considering
themselves as the most magnificent of God’s creations to just another
species of animal and a very recent arrival at that. The problem with the
scientific explanation for evolution is that it challenged the foundations
upon which western culture is based.
Western societies were governed by religious institutions that controlled
not only politics but also the way people viewed nature. The idea that
God made ‘man’ in his image to rule over all other living things was
indisputable. Therefore any challenge to this idea was seen as a threat to
the establishment.
What restrictions were there in society to alternative explanations for the
nature of life on Earth?
_________________________________________________________
_________________________________________________________
Check your answer.
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A variation in viewpoint
The two statements below contrast the way ‘variations among individuals
in a population’ was viewed during ancient Greek times in comparison
with modern biology today.
Ancient Greek – Plato’s view from ‘The Republic’
Each species is a fixed entity that never changes. All individual
variations in a population are unimportant imperfections of the ideal
form. The perfect ‘essence of form’ is made up of the best parts of the
various individuals.
Nineteenth century – Darwin’s view from ‘On the origin of species’
Species have always been changing and always will. Variations among
individuals of a population are necessary for natural selection – the chief
agent of change. It is these very differences between individuals that
make evolution possible and inevitable.
The current view
Since Darwin/Wallace’s explanations for evolution were first proposed,
the science of modern biology was born. Today, biologists use the
principles of evolution by natural selection in their everyday work.
In the Additional resources section, there is a summary of the major
scientific thinkers who have contributed to the modern theory of
evolution. Read these now.
Then complete Exercise 1.7.
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Additional resources
Case study 1: The evolution of kangaroos
Based upon research in Kangaroos: 15 Million years of Australian
bounders by Tim Flannery
“The kangaroos offer a unique opportunity to study evolutionary
changes within a group of Australian mammals”. This is because they
have “the best known fossil record and are the most extensively
studied of all Australian mammals”. Also because they have
undergone rapid evolutionary change and are “commonly good
indicators of restricted environments”.
Tim Flannery
The earliest record of kangaroos is found among the fossils of the
Etadunna formation in central Australia. These deposits were formed
during the late Oligocene to early Miocene epoch, some 25–15 million
years ago.
This region, now a hot dry desert, was cool to temperate and the rainfall
was consistently moderate, with many freshwater lakes and rivers.
It was heavily forested and supported a wide variety of faunas
including many types of marsupials, crocodiles, flamingoes and even
freshwater dolphins.
These early kangaroos were tiny (about the size of a rabbit) and are
believed to have descended from arboreal (tree dwelling) ancestors.
The Musky-rat kangaroo, which lives in the rainforests of north
Queensland, still retains this way of life.
By the middle of the Miocene some 10-12 million years ago, Australia
began to warm up. As time progressed and Australia moved further
north, aridity (dryness) increased and rainfall became seasonal. Forests
began to change and were dominated by eucalypts with some pockets of
open forests and grasslands thriving in the drier conditions. Kangaroos
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41
became abundant, evolving to take advantage of the variety of new
environments emerging from these changes.
They dominated these emerging grassland areas, increasing in size and
rapidly diversifying. The kangaroo fossils of this age show some
evidence of hopping. The fifth toe, which is an adaptation to an arboreal
way of life, has been lost. This can be seen in the diagram of the fossils
showing the paw and toes of a middle Miocene kangaroo.
3
cm
0
A
B
Kangaroo fossils of the middle Miocene showing the paw on the left and
toes adapted for hopping on the right (A, B).
These and other fossils from this period show adaptations to a grazing
mode of life. Among some of these habitats, the modern types of
kangaroo developed.
During the Pliocene period, 5–2 million years ago, the continent
continued to dry out at a faster rate. Rainforests became restricted to the
coastal regions of Victoria, NSW and Queensland. In central
Australia and some coastal areas, woodlands and grasslands had replaced
the rainforests.
The following drawing of a fossil shows the side and top view of
kangaroo molars. Scientists say that they are an adaptation to grazing.
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A
molar
0
molarmolar
3
cm
B
Top and side view of Pliocene fossil, showing molars adapted to grazing.
By the end of the Pliocene and early Pleistocene times, conditions were
even drier than today. Kangaroos evolved bounding strides to take
advantage of the vast grassland plains that had taken over in the arid
areas. This adaptation was to become more important as grasslands
emerged.
The Pleistocene, 1.6 million years ago to the present, saw the evolution
of vegetation that gave rise to the flora that dominates the continent
today. Ice ages were a feature of this period of time. Effects on the
Australian environment were not as dramatic as in the Northern
Hemisphere but they did influence sea levels, which may have fluctuated
some 200 metres. This is significant when considering land bridges,
especially to the north.
This was the time when the well known marsupial megafauna had
evolved. Kangaroos were at their most diverse. They varied from the
giant kangaroos to small types, being adapted to a variety of
environments. As the drying continued, adaptations to overcome long
periods of drought evolved.
Giant kangaroos, wallabies and wombats and the huge Diprotodon would
have been quite a familiar sight among the first humans when they
arrived some 40 000 to 60 000 years ago. Their presence is believed to
have influenced the demise of the megafauna. The Aboriginal practice of
burning further changed the vegetation and favoured grazing species.
European settlers have been responsible for further extinctions, both
because of hunting and through habitat destruction.
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Case study 2: Southern Antarctic Beech
Forests dominated by southern Antarctic Beech, Nothofagus fusca,
persisted in coastal regions of the Antarctic continent until the late
Oligocene. They co-existed with the emerging glaciers (similar to the way
they exist today in southern Chile) until Antarctica froze over completely.
90
0
0
India
Africa
South
America
New Guinea
0
S Antarctica
Australia
New Zealand
Distribution of Nothofagus during the Oligocene.
The diagram following shows the distribution pattern of the Southern
Antarctic Beech (Nothofagus) as it is today. It is found in rainforests in
Tasmania and in the south-eastern Australian mainland. There are also
populations in New Zealand, New Caladonia and New Guinea and also
on the southern tip of western South America.
New Guinea
Australia
New Caledonia
New Zealand
Antarctica
South America
tor
Present day distribution of Nothofagus.
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Fossil records and the modern distribution pattern of the Southern Beech
(Nothofagus) show that it originated on the outer edge of Gondwana
during the late Cretaceous period, around 70 million years ago.
Theories about evolution
For thousands of years, people accepted that living things never change.
There was no need to explain evolution until the evidence that creatures
have changed became overwhelming.
Leonardo Da Vinci (1452–1519)
Leonardo made geological and palaeontologic observations of rocks and
fossils found in north Italy. The fossils were mostly of Cenozoic
molluscs found on the tops of mountains.
Leonardo hypothesised these shell fossils had once been living things and
that they had been buried at a time before the mountains were raised.
It must be presumed that in those places there were sea coasts, where
all the shell were thrown up, broken and divided.
Leonardo’s contribution to our understanding of life was to suggest that
fossils indicated the history of the Earth far beyond human records.
Robert Hooke (1635–1703)
Robert Hooke observed fossils with a microscope and concluded that
shell-like fossils really were ‘the shells of certain shell-fishes.’ He also
observed that many fossils represented extinct organisms. Palaeontology
had become the science that can be used to help understand the history of
life on Earth.
George-Louis Buffon (1707–1778)
George-Louis Buffon published Les Epoques de Ja Nature (1788), where
he suggested that life was much older than 6 000 years as suggested by
the Bible. In his 44 volume publication, Histome Naturelle, Buffon
questioned the Church’s doctrines by proposing that organisms changed.
He did not suggest how but noted that the environment acted directly
on organisms. Buffon goes down in history as having paved the way
for others.
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Carolus Linnaeus (1707–1778)
A Swedish botanist who was the founder of the binomial (two name)
system contributed to evolution by suggesting that species in a genus
have arisen through hybridisation. This is where two different
individuals produce a new kind of offspring.
He originally fought the idea that species had changed and believed they
were all created in the beginning and none had become extinct. Later in
life, he showed that his ideas were changing.
Erasmus Darwin (1731–1802)
A leading eighteenth century intellectual and naturalist, Erasmus Darwin
formulated the first modern theory of evolution in his book, The laws of
organic life.
Describing how one species could evolve into another, he suggested that
sexual selection and competition could cause changes in species.
He wrote:
the final course of this contest among males seems to be that the
strongest and most active animal should propagate the species which
should thus be improved.
He also helped to introduce the concept of adaptation by saying that
organisms are fit for the environment in which they live and that their
structure reflects the functions they perform throughout their lives.
Jean-Baptiste de Lamarck (1744–1829)
Lamarck is always associated with the discredited theory of evolution
where features ‘acquired’ throughout an individual lifetime are inherited
by offspring. Lamarck proposed that an organism develops features by
use or disuse throughout its lifetime. For example, a giraffe develops a
long neck by stretching to eat the leaves of tall trees. This acquired
feature is then passed on to its offspring.
Although wrong, Lamarck’s ideas did pave the way for natural selection
and made a major contribution to the development of evolutionary
thought.
Sadly his theories were ignored and Lamarck died a poor man.
His colleagues even used the eulogy at his funeral to discredit him.
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Alfred Russel Wallace (1823–1913)
Just north of Australia, through the middle of Indonesia and between the
islands of Borneo and Sulawesi, is an imaginary line. This line separates
the islands of Bali and Lombok and is called the Wallace line.
Biologists use this line to describe the separation of Australia flora and
fauna from Asian flora and fauna. It was named after Wallace because of
the observations he did in this region. It was in Indonesia that Alfred
Wallace concluded that species evolved by a process called natural
selection. He wrote to Charles Darwin.
Charles Darwin had independently arrived at the same conclusion after
his extensive observations and work at the Galapagos Islands. The
theory of natural selection was actually proposed by Wallace but has
historically become known as the Darwin/Wallace theory of natural
selection to incorporate the work done by Charles Darwin.
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Charles Darwin (1809–1882)
Charles Darwin was a founder of modern biology and author of the
famous book, On the origin of species. He suggested that plants and
animals in nature produce far more offspring than can survive. Each
individual has its own variety of features. There is a continual struggle
for existence. Those individuals with variations that increase their
chance of survival (the fittest) reproduce more. Hence, this interaction
between a variety of individuals and the harsh environment is the direct
cause of change in species and explains evolution.
Charles Darwin was aware of the social and political upheaval his ideas
may cause. He did not publish his famous book about evolution for
almost 25 years, until Wallace suggested the theory, and Darwin felt
more confident about presenting his observations and thoughts.
Viewpoints about evolution
From the time that the theory of evolution was first presented, it has met
with opposition and misunderstanding. People have tended to react to it
emotionally and philosophically, rather than assessing it as a scientific
explanation that seeks to best explain available evidence.
The theory of evolution does not attempt to undermine religious beliefs
or ideas about the worth of people. Instead, these are non-scientific
arguments that are separate from the debate about whether the theory of
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evolution is supported by sufficient scientific evidence and whether it is,
indeed, the best explanation of that evidence.
The theory of evolution has continued to develop and be refined
throughout the twentieth century, as more and more evidence has been
collected. The theory will continued to be used and examined into the
twenty first century because it remains, to date, the best scientific
explanation of many observations of changes in living things, both past
and present.
Here are some examples of social and political thinking about evolution
for you to evaluate.
Example 1: Cartoons
Cartoons are a common way that social comment is made in newspapers
and magazines. There have been many cartoons drawn about evolution.
Some show organisms slowly changing form over time. For example,
look back at the cartoon in the introduction to this part.
Other cartoons were drawn to ridicule evolutionists. (And some have
been drawn to ridicule people who oppose evolution too.) A famous
cartoon from the 1800s shows Charles Darwin looking like an ape.
From "Darwin as an Ape." Cartoon. 1871.
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Example 2: A view of a nineteenth century scientist
What is man? A profound thinker, Cardinal de Bonald, has said,
‘Man is an intelligence assisted by organs.’ We would fain adopt this
definition, which brings into relief the true attribute of man,
intelligence, were it not defective in drawing no sufficient distinction
between man and the brute. It is a fact that animals are intelligent,
and that their intelligence is assisted by organs; but their intelligence
is infinitely inferior to that of man.
…whence comes man? Wherefore does he exist? …the problem is
beyond the reach of human thought. …but it will be sufficient for our
present purpose to say that it can be shown that man is not derived, by
a process of organic transformation, from any animal, and that he
includes the ape not more than the whale among his ancestry; but that
he is the product of a special creation.
…Let us say that the creation of the human species was an act of God,
that man is one of the children of the great Arbiter of the universe, and
we shall have given to this question the only response which can
content at once our feelings and our reason.
Louis Figuier in his nineteenth century book, The human race.
Example 3: A modern view
You may be able to borrow a book by Stephen J Gould that includes
information about some of these social and political influences.
You could also look at some of the many Internet sites on this subject.
You’ll find plenty of information in favour of and opposed to the theory of
evolution. You will find some helpful starting points on the Science online
webpage at: http://www.lmpc.edu.au/science
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Suggested answers
Adaptations to suit environments
Changes in the environment put pressure on the species living there.
Species with features that enable them to survive will thrive and
reproduce while those without the adaptations for survival become
extinct.
Earth’s constantly changing environment
1
2
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Features of the environment that may change include:
•
available water – wetter or drier
•
temperature – hotter or colder
•
pH – more acidic or more alkaline
•
available space - less space or more space
•
concentration of dissolved minerals
•
introduction of a new more competitive species
•
competition from members of the same species.
Some other features are also included in the following table.
Physical
Chemical
Changes to competition
•
changes in
temperature
•
•
predatory competition introduction
of prey/predator
•
changes in
pressure
availability of
gases such as
oxygen or
carbon dioxide
•
lack of space
changes in
light
•
changes to pH
•
•
competition from members of the
same species
•
changes to
salinity
•
disease
51
3
a) Adaptations for an area drying out include: a skin coating or
cover to prevent desiccation, more concentrated urine and less
surface area of leaves in plants.
b) Adaptations for a new species of poisonous frog include:
resistance to the poison and seeking alternative food sources.
c) Adaptations for increased salinity include: the ability to absorb
water by active transport and the ability to excrete salt as a
waste.
The fossil record of horses
24
11
20
17
17
12
S pa n o f c h e e k t e e t h ( i n c m )
16
12
10
15
9
12
7
13
6
5
8
4
1
2
16
16
13
9
14
5
4
8
3
4
0
60
Middle
EOCENE
Late
Early Middle Late
40
OLIGOCENE
Early
30
Middle
MIOCENE
Late
Early Middle Late
10
PLIOCENE
1 0
Millions of years ago
52
PLEISTOCENE
Early
1
They have descended from a common ancestor and did not give rise
to one another at the same time.
2
The span is becoming longer in length.
3
There is diversity in the teeth span: some less, some more.
4
They may have originated from the same ancestor as Miohippus.
5
There are many valid interpretations.
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6
Here are two possible alternative answers.
24
11
20
17
S pa n o f c h e e k t e e t h ( i n c m )
17
12
16
12
10
15
9
12
8
4
1
2
13
9
6
5
16
16
7
13
14
5
4
8
3
4
0
Middle
Late
EOCENE
60
Early Middle Late
40
OLIGOCENE
Early
Middle
Late
MIOCENE
30
Early Middle Late
PLIOCENE
10
Millions of years ago
PLEISTOCENE
Early
1 0
24
11
20
17
S pa n o f c h e e k t e e t h ( i n c m )
17
12
16
12
10
15
9
12
16
7
6
5
8
4
1
2
13
9
16
13
14
5
4
8
3
4
0
60
Middle
EOCENE
Late
Early Middle Late
40
OLIGOCENE
Early
30
Middle
MIOCENE
Late
Early Middle Late
10
PLIOCENE
Millions of years ago
6
Part 1: Evolution
PLEISTOCENE
Early
1 0
To decide which graph is best (yours or either of the ones above),
you would need to use data from other characteristics of these
organisms, not just the span of their cheek teeth.
53
Your answers for the following questions depend upon how similar your
graph is to the ones shown.
7
4 cm
8
About 10.5 cm
9
The horse evolves slowly at first, then, after a series of rapid
diversifications, evolves quickly.
10 Many organisms don’t preserve very well. Life forms, as recorded
in fossils, are still only a fraction of the number that have ever lived.
We are only just finding new techniques for determining the makeup
of past life forms. With further development in these areas, more
knowledge will be obtained.
Transitional fossils
Scientists want to find the steps that led from one life form to another.
Although most modern scientists do not expect to find real transitional
forms – in between organisms – they continue to search for evidence of
evolution.
Biogeography as evidence for evolution
The borders of the biogeographic zones are oceans and mountain ranges.
Wallace’s line
Most vertebrates, apart from birds and bats, are restricted to regions
bordered by coastlines and mountain ranges. Flowering plants have
dispersal methods which enable them to be distributed beyond these
limiting barriers.
Six degrees of separation
In order from most different to least different are: 1 Australian (8),
2 Ethiopian (6), 3 Neotropical (5.3), 4 Nearctic (1.3) and Oriental (1.3),
and 6 Palaearctic (0.6).
Comparative embryology
The middle row is the most similar.
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Biochemistry
1
a) chimpanzee
b) yeast
2
The more closely related the species, the fewer number of amino
acid differences.
Other evidence – divergent evolution
1
Amphibians reproduce in water and their early stages of
development require a life in water.
2
Insects and other arthropod groups could live inland.
3
Dinosaurs reproduced by internal fertilization and laid eggs.
4
Ecosystems left vacant by the perishing dinosaurs enabled mammals
to diversify and establish themselves in new specialised niches.
They had plenty of food and little competition for resources.
5
Divergent evolution is when one group or species evolves into two
or more groups to occupy new niches.
Convergent evolution
1
The physical feature that they all have is a streamlined body. This is
an adaptation for overcoming the viscosity of water.
2
Moving about through water swiftly is important for the survival of
these animals. Natural selection has selected animals which have
evolved to this shape so these very different animals look much the
same.
The evolution of evolution
Politics was centred around the beliefs of the church. Alternative
explanations were against the dogma of the church; therefore they
challenged the establishment.
Accepting an idea such as evolution of species required people, including
scientists, to sort through many issues, including what science is, what
religion is and why human society is organised in particular ways.
Part 1: Evolution
55
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Exercises – Part 1
Exercises 1.1 to 1.7
Name: _________________________________
Exercise 1.1: Earth’s constantly changing environment
a)
List some physical conditions that might change in the environment.
_____________________________________________________
_____________________________________________________
b) List some chemical conditions that may change in the environment.
_____________________________________________________
_____________________________________________________
c)
How might these changes impact on the evolution of plants and
animals? Choose two physical changes and two chemical changes
that you have listed and outline their effects.
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
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Exercise 1.2: An open-ended investigation of natural
selection
Describe an open-ended investigation that you have done that illustrates
natural selection.
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
Exercise 1.3: A case study
Name of Australian species studied: ____________________________
Describe changes in this species that have occurred over time because of
environmental changes.
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
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Exercise 1.4: Wallace’s line
The Wallace line falls between Borneo and Sulawesi and between the
tiny islands of Bali and Lombok. The latter pair of islands is separated
by a mere 30 km, but for the most part they are inhabited by different
families of mammals and even different birds.
Philippines
Celebes
Sea
Sabah
Limit of native placental
mammals other than bats,
Muridea, Sus and Cervus
Pacific Ocean
Limit of marsupials
0
Borneo
1000 km
Sulawesi
Irian Jaya
Wa
llac
e ’s
Lin
e
Halmahera
Papua
New Guinea
Banda Sea
Sumbawa
Flores
Timor
Arafura Sea
Timor Sea
Australia
Gulf of
Carpentaria
Australia
a)
How would you account for these differences?
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
b) How did these observations influence Wallace to propose his theory
of evolution?
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
Part 1: Evolution
59
Exercise 1.5: Comparative anatomy
a)
Compare the finger bones labelled 1, 2, 3, 4 and 5 for a bat, human,
whale, lizard, cat, frog and bird by filling in the following tables.
The first entry in each table is done for you.
humerus
Bat
humerus
ulna
Human
radius
humerus
carpal
radius
1
Bird
radius
ulna
ulna
carpal
5
5
carpal
humerus
1
4
4
2
radius
ulna
1
3
2
carpal
Whale
5
3
4
3
1
2
3
2
Lizard
humerus
humerus
Cat
Frog
ulna
humerus
radius
radius
radius
1
ulna
ulna
carpal
2
3
5
carpal
carpal
4
1
2
1
5
3 45
2
4 3
Fingerbones of vertebrates.
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÷) or absent (x)
Fingerbone present (÷
Organism
frog
1
2
3
4
5
÷
÷
÷
÷
÷
lizard
bird
cat
bat
whale
human
Analyse how the structure is related to the function of each by filling in
the following table.
Organism
Function of limb
frog
limb used for support and cleaning
lizard
bird
cat
bat
whale
human
Part 1: Evolution
61
b) Compare the structure of the pentadactyl limb for three of the above
vertebrates.
______________________________________________________
______________________________________________________
______________________________________________________
______________________________________________________
______________________________________________________
______________________________________________________
______________________________________________________
______________________________________________________
______________________________________________________
______________________________________________________
______________________________________________________
c)
How would an evolutionary biologist explain the pentadactyl features?
______________________________________________________
______________________________________________________
______________________________________________________
______________________________________________________
______________________________________________________
______________________________________________________
______________________________________________________
______________________________________________________
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Exercise 1.6: Other evidence
Describe how the finches of the Galapagos Islands are an example of
divergent evolution.
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
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63
Exercise 1.7: The evolution of evolution
a)
Do your own research on the historical development of theories of
evolution. You can also use the material in the Additional resources
section titled ‘Theories about Evolution’. Present your information
in the table below.
Identify the data source(s) you used.
______________________________________________________
______________________________________________________
______________________________________________________
Name of scientist
Dates
Contribution
Leonardo Da Vinci
Robert Hooke
George-Louis Buffon
Carolus Linnaeus
Erasmus Darwin
Jean-Baptiste de
Lamarck
Alfred Russel Wallace
Charles Darwin
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b) Do your own research on social and political influences on the
development of the theory of evolution. (You can also read the
information in the Additional resources section.)
How do you think social conditions and political ideas have affected
the development and acceptance of an evolutionary explanation for
life on Earth?
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
Part 1: Evolution
65