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EVOLUTION
SBI3U/3C
M. St Denis
Charles Darwin – 1809-1882
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An English Biologist
Fascinated by different species
and fossils.
Traveled around the world on
the BEAGLE and headed to
the FAMOUS GALAPAGOS
ISLANDS
GALAPAGOS ISLANDS
GALAPAGOS ISLANDS
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The Galapagos islands are isolated
encrusted with lava and home to the
worlds most bizarre creatures found
nowhere else on Earth
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Tortoises that reach giant sizes
Land dwelling lizards that take to the sea
Vampire finches that suck the blood of
other birds rather than eating seeds.
GALAPAGOS ISLANDS
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The unusual species on the island have long
fascinated biologists.
Once such biologist was the young Charles Darwin,
who visited the Galapagos as part of his
remarkable 5 year journey on the ship the beagle
On this trip, Darwin collected specimens and made
observations.
What is Evolution?
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Evolution is:
the relative change in the
characteristics of populations
that occurs over
successive generations
Diversity of Life
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Diversity is the cornerstone of evolutionary biology
Not all individuals of a species are exactly alike
Differences between individuals are not always
immediately visible
Diversity is important for the long term survival of a
species
Biodiversity
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Differences in characteristics between individuals
may be:
 Advantageous
 Harmful
 Neutral
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Characteristic may not give an individual an
advantage now, but may become critical for
survival later if the environment changes
What controls the characteristics of
individuals?
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Genes!!
There are different versions of genes, known as
alleles, in a population which is the basis of
biodiversity.
Gene pool
– total of all genes in a population
What is Evolution?

Evolution is
 the
relative change in the characteristics of
populations that occurs over successive
generations
 any
shift in the gene pool of a population
 ratio
of characteristics in a population change
over successive generations
Who can evolve?
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Individuals cannot evolve!
 Individuals
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cannot change their genes.
Populations are the smallest unit that can
evolve.
 Populations
pool.
can have a shift in their gene
Why would populations evolve?
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So that a population becomes better
suited to its habitats.
 Increased
survival
 Better chance of passing on characteristics to offspring.
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Takes place over many generations.
How does a population evolve?
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A shift in the gene pool so that a higher ratio of
individuals have a particular adaptation.
Adaptation
a
particular structure, physiology or behaviour that
helps an organism survive and reproduce in a
particular environment.
 e.g.
camouflage, superb sense of smell, bill shape
Example of a population that evolved:
Peppered moths in England
The Peppered Moth
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The peppered moth has two colour forms:
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A light form and a dark form
Moth color is an inherited characteristic.
Many moths are eaten by birds, which usually select the
moths that differ most in colour from the trees on which
the moths rest.
Thus, in regions where soot darkens the bark of trees,
moth populations evolve to consist mostly of dark moths.
What did Darwin’s
Travels reveal
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The diversity of living
species was far greater
than anyone had
previously known!!
These observations led him
to develop the theory of
evolution!!
3.How did tortoises and birds differ among
the islands of the Galapagos?
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Each island
had its own
type of
tortoises and
birds that were
clearly
different from
other islands
Galapagos
Turtles
Evolution is when organisms change over time. So, modern
organisms descended from ancient ones
Geologists:
Hutton and Lyell
Fundamentalists said that the earth
was around 6000 years old
Hutton and Lyell argued that the
earth is many millions of years old
b/c
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layers of rock take time to form
processes such as volcanoes and
earthquakes shaped the earth and
still occur today
Lamark
Theory of acquired characteristics
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Lamark said organisms
acquired traits by using
their bodies in new
ways
These new
characteristics were
passed to offspring
Lamark was totally
wrong!
Evolution is a Theory – Just like Gravity!
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Evolution is a well
supported explanation
of phenomena that have
occurred in the natural
world
A theory in science is a
well tested hypothesis,
not just a guess
Malthus
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Reasoned that if the human
population continued to grow
unchecked, sooner or later there
would be insufficient living
space and food for everyone
There will be a struggle for
survival between the members of
the population
Individuals with advantageous
variations will breed and produce
more offspring
Darwin finally published his
ideas in 1859
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Other naturalists
were developing the
same theory that
Darwin did.
Even though he was
afraid of the Church’s
reaction to his book
he wanted to get
credit for his work.
Artificial Selection
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nature provides variation, humans select variations
that are useful.
Example - a farmer breeds only his best livestock
Natural Selection
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The traits that help an
organism survive in a
particular environment
are “selected” in
natural selection
Natural Selection and Species Fitness
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Overtime, natural selection results in changes in
the inherited characteristics of a population.
These changes increase a species fitness
(survival rate)
Descent with Modification
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Each living species
has descended with
changes from other
species over time
Summary of Darwin’s Theory
1. Organisms differ; variation is inherited
2. Organisms produce more offspring than survive
3. Organisms compete for resources
4. Organisms with advantages survive to pass those
advantages to their children
5. Species alive today are descended with
modifications from common ancestors