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Natural selection is a theory
developed by Charles Darwin
• Individuals whose physical
and behavioral
characteristics are best
adapted to their
environment (habitat)
have better chances of
reproducing and passing
on their DNA to future
generations.
Video
Class Starter
1. Describe the theory of natural selection in your
own words.
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2. Explain how the same members of a species can
develop different traits.
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Example of Natural Selection
- 2 variations of the peppered moth
• light variation is best adapted to living in the
country (it camouflages with the birch trees)
• dark variation is best adapted to living near
factories (where tree trunks have turned black
due to the factory smoke)
Light Peppered Mothbest adapted to living in the country
Black peppered mothbest adapted to living near factories
How did the black moth come to be?
The black moth arose as a result of a genetic
mutation in the gene responsible for wing
colour.
How do members of the same species
develop different traits?
1. Genetic Mutations
– Every time your DNA replicates in order to
make new cells it can make mistakes
– These mistakes result in changes to your DNA
and thus changes to your physical traits.
– A new trait might be more successful in a
specific environment, causing it to become
more frequent in the population
Genetic Mutations
How do members of the same species
develop different traits?
2. Sexual reproduction:
– Parents pass on their traits to their offspring
through their DNA.
– Each offspring inherits a different
combination of their mother and father’s
genetic information (genes).
Different Combinations of Genes
How do members of the same species
develop different traits?
• Certain offspring may be born with a
combination of genes that is more successful
than his/her parents or siblings.
• This will make the individual ‘more fit’ and
therefore more likely to survive in their
environment and pass on their DNA to future
generations.