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YEAR 10 SCIENCE
LESSON 1: EVOLUTION
Lesson 1 Syllabus Reference

Outcomes
A student

Explains how biological understanding has advanced through scientific
discoveries, technological developments and the needs of society.

Content
The theory of evolution by natural selection explains the diversity of living things and
is supported by a range of scientific evidence.
Students:
a. Describe scientific evidence that present-day organisms have evolved from
organisms in the past.
b. Relate the fossil record to the age of the Earth and the time over which life has
been evolving.
c. Explain, using examples, how natural selection relates to changes in a population,
eg in the development of resistance of bacteria to antibiotics and insects to
pesticides.
d. Outline the roles of genes and environmental factors in the survival of organisms
in a population.
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YEAR 10 SCIENCE
LESSON 1: EVOLUTION
1.
History of Evolution

Quick review of evolution

In a very broad sense, evolution simply means ‘change over time’.
However, this is not a very good working definition for purposes of Biology.
–
This is because many processes in nature involve ‘change over time’,
yet we would not classify them as ‘evolution’. Can you think of any
examples?1
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
A better, but still very simple, definition of biological evolution is changes in
a population of a species over a long period of time.

This brings us to modern evolutionary theory which holds that all organisms
descended from a single common ancestor.
–
This means that all organisms are related, if very distantly in some
cases.
–
This concept is often referred to as the ‘Tree of Life’.
Source: http://tbi.montana.edu/outreach/hotscience/materials/
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YEAR 10 SCIENCE

LESSON 1: EVOLUTION
In the diagram on the previous page, where would the common ancestor
be? Label it in the appropriate place on the tree.2

The complex diagram below illustrates just how complicated the evolution
history is!
–
Can you identify which part of the diagram humans belong in?
–
Label the earliest common ancestor in this diagram.
http://www.randalolson.com/research/

Watch a VIDEO (Length 6:29) about the Tree of Life (David Attenborough).
–
When is life first thought to have begun?3
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YEAR 10 SCIENCE

LESSON 1: EVOLUTION
Important scientists

Jean Baptiste Lamarck
–
Lamarck was a French naturalist who made important early
contributions to evolutionary theory.
–
He believed that adaptations were developed by individual organisms
based on inner ‘need’, becoming acquired characteristics which were
passed on to offspring directly.
–
For example, Lamarck thought that giraffes’ necks became longer
between generations if parent giraffes had to stretch their neck further to
reach higher leaves on trees.
Source: http://sabrinafair2.tripod.com/evolutionproject/id9.html
–
Based on Lamarckian theory, describe what your offspring would look
like if you went to the gym every day and became a bodybuilder.4
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–
Generally speaking, Lamarck’s theory has been proven to be incorrect
and has been largely replaced by Darwin’s theory.
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YEAR 10 SCIENCE

LESSON 1: EVOLUTION
Charles Robert Darwin
–
Darwin was an English naturalist with an intense passion for studying
the natural world.
–
Darwin developed his ideas and gathered evidence while aboard the
H.M.S. Beagle on a British science expedition around the world.
–
In South America, Darwin found fossils of extinct animals that were
similar to modern species. On the Galapagos Islands he noticed
many variations among plants and animals of the same general type as
those in South America.
–
His real legacy was not proposing the idea of evolution; that was old
news.
–
Darwin’s real breakthrough came in proposing a mechanism for
evolution: the process of natural selection.
Source: http://beforeitsnews.com/science-and-technology/2012/03/darwins-h-index-1847177.html
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YEAR 10 SCIENCE

LESSON 1: EVOLUTION
Upon his return to London, Darwin theorised that:
a)
gradual change over time did occur
b)
evolutionary change was very slow, requiring thousands to millions of
years
c)
variation in a species occurs randomly and can be due to mutation
d)
the survival of each organism is due to its ability to cope in a
changing environment i.e. the primary mechanism for evolution was
natural selection
e)
the millions of species alive today all arose from a single original life
form through a branching process called speciation
–
In 1859, Darwin wrote his famous book called On the Origin of Species.
–
Watch a short VIDEO (Length 3:37) on Darwin. How do you think
society and politics may have affected the development of the theory of
evolution over time?5
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Source: http://www.mun.ca/biology/scarr/Mans_Place_in_Nature.html
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YEAR 10 SCIENCE
LESSON 1: EVOLUTION
2.
Darwinian Evolution

Darwinian theory of evolution

The Darwinian Theory of Evolution proposes that evolution occurs as a
function of “survival of the fittest”.
–
How do you think we measure fitness? What would be the single most
important factor for scientists in determining if an organism is ‘fit’?6
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
This theory states that:
–
More offspring are produced than can survive in a population, and, as
population size tends to remain relatively constant, many offspring must
die.
Source: http://evolution.berkeley.edu/evolibrary/article/evo_25
–
Thus, there is a struggle for existence where the individuals who are
better adapted to their environment will survive so that they have the
opportunity to reproduce and pass on their genes to their offspring.
Source: http://evolution.berkeley.edu/evolibrary/article/evo_25
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YEAR 10 SCIENCE
–
LESSON 1: EVOLUTION
Over long periods of time (remember, life is thought to be 3.5 billion
years old!), the more suited adaptations or favourable traits of
individuals will become prevalent in the population.
Source: http://evolution.berkeley.edu/evolibrary/article/evo_25
–
Gradually, as new adaptations accumulate, the population will become
very different – maybe even with new species.
How would you be able to tell if the changed population was a new
species?7
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NOTE TO STUDENTS:

Evolution is the theory which explains how species evolve over time.

It is not a theory which explains the origins of life.

This is a common misconception both among scientist and theologians in
the ongoing debate of creation versus evolution.
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form, or by any means (electronic, mechanical, photocopying, recording, or otherwise), without the prior permission of Matrix Education.
YEAR 10 SCIENCE

LESSON 1: EVOLUTION
The following flow-chart should be used when answering questions on
evolution.
VARIATION a in population
SELECTION PRESSURE
DEATH of poorly adapted
organisms (with
unfavourable
characteristics)
SURVIVAL of well-adapted
organisms (with favourabe
characteristics)
REPRODUCTION - passing
on the favourable
characteristics to offspring
DOMINANCE - majority of
the population contains the
favourable characteristics
NOTE TO STUDENTS:

Flow charts are a great way to organise and present processes in science.

You may be asked to draw flow charts to outline different processes in your
workbook questions and even in later on, in HSC questions!
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form, or by any means (electronic, mechanical, photocopying, recording, or otherwise), without the prior permission of Matrix Education.
YEAR 10 SCIENCE
LESSON 1: EVOLUTION
3.
Divergent and Convergent Evolution

What is a ‘species’?

The word ‘species’ gets thrown around quite a lot, but surprisingly it is often
misunderstood. See if you can write a definition for species below:8
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
You need understand two important processes that are often discussed
when mentioning species:
(i)
Divergent evolution and;
(ii)
Convergent evolution.
–
In a very general sense, what does it mean for something to “diverge”?
Draw a diagram of lines diverging.9
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–
What does it mean to “converge?” Draw a diagram of lines converging.10
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form, or by any means (electronic, mechanical, photocopying, recording, or otherwise), without the prior permission of Matrix Education.
YEAR 10 SCIENCE

LESSON 1: EVOLUTION
Divergent evolution

Divergent evolution is the process where two or more related species
become less similar – that is, they diverge.
–
It can develop to the point where one species slowly evolves over time
into two (or more) different species.

If this process of divergent evolution continues to the extent of creating a
number of distinct species from a single common ancestor, the process
is referred to as adaptive radiation.
–
The ancestral species have been subjected to divergent evolutionary
mechanisms a number of times and each new species has ‘adapted’ and
‘radiated’ out to fill specific ecological niches (e.g. eating from specific
food sources).
–
Darwin’s Galapagos finches are the prime example.
Source: http://mayhewbiology.com/Biology%20notes/speciation%20notes.htm
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form, or by any means (electronic, mechanical, photocopying, recording, or otherwise), without the prior permission of Matrix Education.
YEAR 10 SCIENCE

LESSON 1: EVOLUTION
Convergent evolution

Convergent evolution is the process by which unrelated (or only distantly
related) organisms evolve to become more similar in some regard (e.g.
body form, colour, behaviour, organs, etc.).
–
This is caused by the unrelated organisms being subjected to similar
environmental conditions or ecological niches.
–
A classic example of convergent evolution is the presence of wings in
bats, birds, and insects.
Source: http://archive.peabody.yale.edu/exhibits/treeoflife/convergent.html
–
These organisms are only very distantly related as their last ‘common
ancestor’ would have been a very simple multicellular organism from
many hundreds of millions of years ago WITHOUT any wings.
–
This means the wings have arisen independently in each group of
organisms (bats, birds, and insects) due to environmental conditions,
allowing them to exhibit similar behaviours (flying).
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YEAR 10 SCIENCE

LESSON 1: EVOLUTION
PLEASE NOTE: Convergent evolution does NOT state that the organisms
are evolving into one another – bats are not slowly becoming birds or even
more ‘bird-like’.
–
Convergent evolution simply states that birds and bats have developed a
similar trait (wings) and behaviour (flying) as a response to similar
environmental conditions and to fill specific ecological niches.

Another good example of convergent evolution is the long list of similarities
between various marsupial and placental mammals. See the table below.
–
These mammals are similar in body form as well as habitat
requirements.
Source: http://www.tokresource.org/tok_classes/biobiobio/biomenu/evolution/page14.jpg
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YEAR 10 SCIENCE
LESSON 1: EVOLUTION
4.
Evidence for Evolution

Palaeontology

Recall that paleontology refers to the study of fossils. Here is a fossil of
some ammonites found in some limestone.
Source: http://www.geocaching.com/geocache/GC4M7Y5_limestone-fossils-rockwood
–
What are fossils? And what are some examples?11
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Can you remember how fossils form?12
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YEAR 10 SCIENCE

LESSON 1: EVOLUTION
Unfortunately, the chances of fossilisation occurring are relatively low.
–
Most plants and animals leave no trace of their existence, and those
that do are rarely found.
–
This means that we have an incomplete fossil record of the organisms
that lived in the past.

By studying the fossil record, the evolution of different species can be
traced over time.
–
The fossil record shows a change from simple organisms in the oldest
rocks, to complex organisms in the youngest rocks.
Source: http://www.dmp.wa.gov.au/11881.aspx
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YEAR 10 SCIENCE

LESSON 1: EVOLUTION
When tracing the evolution of organisms through time, scientists often
search for transition fossils. What do you think a transition fossil is?13
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
Archaeopteryx was the first real example of a transitional fossil, and is
probably still the best known.
–
It is “half-way” between birds and reptiles.
–
It had fully formed feathers, but otherwise had reptilian/dinosaur-like
characteristics.
Source: http://www.adirondackwildlife.org/Feathers_or_Flight.html
–
Explain why the Archaeopteryx is considered a transitional fossil.14
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