Download On the origin of species by means of natural selection,

ON THE ORIGIN OF SPECIES
BY MEANS OF NATURAL
SELECTION,
Or the preservation of favoured races in the
struggle for life
FIRST: THE SE
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The SE is in exactly 2 weeks time!
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January 21st
Next lesson, or the lesson next week, we will
discuss the previous SE.
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This won’t take all lesson
THE ORIGIN OF SPECIES BY MEANS OF
NATURAL SELECTION
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What does that mean?
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http://www.youtube.com/watch?v=aTftyFboC_M
THE ORIGIN OF SPECIES
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Ancient view:
God created the world and all the plants and
animals in it
 Species are fixed
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Darwin’s view:
 Species are not fixed!
 Species can adapt to new environments through
the process of ‘natural selection’ (and sexual
selection…)
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NATURAL SELECTION
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What is natural selection?
Animals (on which we mainly focus) reproduce
sexually
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What is sexual reproduction?
Offspring get half their genes from the father,
half their genes from their mother
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This creates a lot of variation
NATURAL SELECTION
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This means that some of the offspring may be
better adapted to the environment they are born
in
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This increases their chance of survival!
Is this enough?
No
 Why not?
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They need to be able to pass their genes on to the
next generation!
SURVIVAL OF THE FITTEST
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What is meant with the ‘fittest’?
FITNESS
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“the ability of an organism to produce viable
offspring capable of surviving to the next
generation”
Animals with a high fitness are able to pass their
genes on to the next generation. Therefor those
genes continue to exist. If an animal fails to
reproduce, his genes disappear
This is why natural selection acts on the level of
the gene!
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To be continued!