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Transcript
Ideas that Shaped
Darwin’s Theory of
Evolution
1) The influence of Geology


Charles Lyell demonstrated that the Earth was
very old and that it changed over time
Darwin thought that if the earth could change, so
could life on earth
2) The influence of Farmers:
Artificial Selection

Artificial Selection =
technique
in which
Meet
the the
intervention
HUMANS
Superof Cow
allows only selected
organisms to exist
2) The influence of Farmers:
Artificial Selection


Farmer altered and improved crops and livestock
through breeding programs (eg. High yielding
diary cows)
Darwin thought that if farmers could artificially
select organisms, then nature (without human
intervention), maybe also select organisms best
suited to the environment to survive and
reproduce
3) The Influence of Thomas
Malthus (1766-1834): Population
Controls

Malthus observed that babies were being born
at a faster rate than people were dying, and
that sooner or later there wouldn’t be enough
living space and food
3) The Influence of Thomas
Malthus (1766-1834): Population
Controls


To prevent endless population growth, famine,
disease and war would need to occur
Darwin knew that animals produced many
offspring, but few survived; he thought that nature
must determine that only some individuals
survive and reproduce
Evolution of Natural Selection
(Darwin)

Natural Selection = process in nature that results
the most fit organisms producing offspring

It is believed that natural selection operates
similar to artificial selection but over longer
periods of time and without any controls or
purpose

Individuals whose characteristics are well
suited to their environment survive,
individuals whose characteristics are not
well suited to their environment either die
or leave fewer offspring. Darwin called this
“SURVIVAL OF THE FITTEST”
Raptors
Ice age
Natural Selection in Peppered moths
 Light
colored moths were most common before
the industrial revolution in England. After trunks
of tress had been stained by pollution, the dark
colored moths became more common
Peppered Moths and Industrial
Melanism

The second half of the twentieth century
saw widespread implementation of
pollution controls, thus trends reversed
and light colored moths again dominated.
pollution created generally darker environment
 Clean up created a generally lighter environment

Selection Against Melanism

We may also call this ACCIDENTAL
SELECTION which is the result of human
activity which changes the genetic
character of organisms. Another example
is bacteria that are resistant to antibiotics.
Peppered Moths video
Comparing Darwin’s and
Lamarck’s views