From the previous lesson on mutation you
should be able to:
• state what mutations are
• explain how mutations occur
Adaptation, natural selection and the evolution of species
In this lesson you should learn about the
process of natural selection and how it
explains why organisms evolve.
Success criteria:
• Describe the process of natural selection
• Explain how it is involved in the evolution
of organisms
Adaptation, natural selection and the evolution of species
In a previous topic you learned about
variation in species.
What types of variation were there?
Discrete and continuous.
How was variation produced in a species?
Through the process of sexual reproduction.
Adaptation, natural selection and the evolution of species
The variation that exists in a population allows
environmental factors to have an influence on the
population.
This process is called Natural selection and it
determines which organisms survive to reproduce.
Adaptation, natural selection and the evolution of species
The Theory of Natural selection
Controversially proposed by
Charles Darwin in his
Book ‘On the Origin of Species’
in 1859.
But other scientists had similar ideas like Alfred
Russell Wallace
http://www.twigonglow.com/films/darwins-dilemma-1144/
Adaptation, natural selection and the evolution of species
http://www.twigonglow.com/films/natural-selection-1140/
Natural selection (survival of the fittest)
• Organisms reproduce producing many offspring
• Variation exists among the offspring
• Individuals struggle to survive in their
environment
• Only the “fittest” survive as they are better
adapted
• These survivors reproduce passing on their
successful genetic information (alleles)
Adaptation, natural selection and the evolution of species
Darwin explained that those organisms best
adapted for their environment would survive
and reproduce.
Those not well adapted would not survive and
eventually would be disappear.
Darwin’s problem was he could not give a clear
living example but used his observations
particularly of Finches in the Galapagos Islands.
Adaptation, natural selection and the evolution of species
Darwin’s finches support the idea that organisms
change with selection pressure.
In the finches case it was to evolve different beak
shapes and sizes as mutations allowed them to
make use of different food sources.
One original group of finches slowly spread to
different islands and evolved to be best
adapted to the food on their island.
Adaptation, natural selection and the evolution of species
Darwin’s Finches
Adaptation, natural selection and the evolution of species
A modern example
of Natural Selection
in action is the
Peppered Moth
(Biston betularia)
Adaptation, natural selection and the evolution of species
Two forms of the moth exist pale and
dark.
The distribution of the different forms
is determined by the environmental
pressure of pollution.
Pollution levels alter the colour of the
trees (soot and a change in lichen
numbers).
This alters the camouflage effect of
the different forms and this alters the
numbers surviving.
Adaptation, natural selection and the evolution of species
In towns and cities where there is a lot of pollution
the lichens on trees die and soot often covers the
trees making them dark.
More dark coloured forms of the moth will be
present. (WHY?)
In towns and cities where there is less pollution
light coloured lichens will survive and less soot
will cover the trees.
More of the light coloured form will be found. (WHY?)
What do you think happens in the rural areas?
Adaptation, natural selection and the evolution of species
Bacterial resistance to antibiotics is also an
example of modern natural selection.
Can you think why this is?
Adaptation, natural selection and the evolution of species
Adaptations that have evolved through natural
selection
Adaptations can either be structural, physiological
or behavioural.
Watch the video clips and make a note of the
adaptations and whether they are structural,
physiological or behavioural.
You may need to watch them twice.
http://www.twigonglow.com/films/life-in-hot-deserts-1129/
http://www.twigonglow.com/films/life-in-the-freezer-1128/
http://www.twigonglow.com/films/bizarre-adaptations-1132/
Adaptation, natural selection and the evolution of species
Other adaptations that help animals survive in
their environment (for discussion).
Adaptation, natural selection and the evolution of species
Other adaptations that help animals survive in
their environment (for discussion).
Adaptation, natural selection and the evolution of species
Other adaptations that help plants survive in
their environment (for discussion).
Adaptation, natural selection and the evolution of species
In this lesson you should have learned about
the process of natural selection and how it
explains why organisms evolve.
• Describe the process of natural selection
• Explain how it is involved in the evolution
of organisms
Adaptation, natural selection and the evolution of species