Transcript RevLessAQA_GCSESciB1_8PPt

AQA GCSE Science & Additional Science
Biology 1 Topic 8
Evolution
Evolution
Hodder Education Revision Lessons
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AQA GCSE Science & Additional Science
Biology 1 Topic 8
Overview
• Particular genes or accidental changes in the genes of plants
or animals may give them characteristics that enable them to
survive better. Over time this may result in entirely new
species.
• There are different theories of evolution. Darwin’s theory is
the most widely accepted.
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AQA GCSE Science & Additional Science
Biology 1 Topic 8
Darwin
Darwin’s theory of evolution by natural selection states that all
species of living things have evolved from simple life forms that
first developed more than 3 billion years ago.
This is a theory and because of the timescales involved it is
unlikely to be ever proven.
Do you believe Darwin’s theory?
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AQA GCSE Science & Additional Science
Biology 1 Topic 8
Galapagos finches
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AQA GCSE Science & Additional Science
Biology 1 Topic 8
Darwin’s theory barriers
Many people refused to accept Darwin’s theory because:
• it was in conflict with religious views that God had created the
universe and all creatures in it
• there was insufficient evidence to support the theory —
Darwin had developed his ideas from finches on the
Galapagos Islands; little other research had taken place
• the mechanisms of inheritance and genes were not known
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AQA GCSE Science & Additional Science
Biology 1 Topic 8
Other theories
Other theories, including that of Lamarck (working before
Darwin), are based mainly on the idea that changes that occur
in an organism during its lifetime can be inherited.
We now know that, in the vast majority of cases, this type of
inheritance cannot occur.
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AQA GCSE Science & Additional Science
Biology 1 Topic 8
Lamarck’s theory
Lamarck thought that
herons had evolved long
legs because they
stretched their legs to
stay dry, as shown.
They would then pass on
these acquired
characteristics to the next
generation.
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AQA GCSE Science & Additional Science
Biology 1 Topic 8
Classification
Evolution and patterns of change can be studied effectively only
if organisms are carefully defined and their relationships
understood.
Living organisms are classified into:
• animals
• plants
• microorganisms
What do these terms mean?
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AQA GCSE Science & Additional Science
Biology 1 Topic 8
Natural selection — theory
Evolution occurs via the process of natural selection:
• Individuals within a species may show a wide range of
variation because of differences in their genes.
• Individuals with characteristics most suited to the
environment are more likely to survive and breed
successfully.
• Those genes responsible for the survival characteristics are
then passed down to the next generation.
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AQA GCSE Science & Additional Science
Biology 1 Topic 8
Natural selection — practice
Explain, using the theory of natural selection, what may happen
in the following scenario:
Giant tortoises live on an island and eat ground plants and the
leaves of bushes. Genetic variation means that some tortoises
have longer necks than others. Normally there is plenty of food
to go round but one year there is a big drought and food is in
short supply.
Why might future generations of tortoises have more
individuals with longer necks?
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AQA GCSE Science & Additional Science
Biology 1 Topic 8
Mutations 1
Mutations are random genetic alterations. They can cause an
extreme change in the characteristics of an organism.
If such a mutation is coupled with a change in the
environment, there can be a relatively rapid change in that
species.
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AQA GCSE Science & Additional Science
Biology 1 Topic 8
Mutations 2
Olaf Leillinger
One example of a mutation and a rapid change is the peppered
moth. Explain it.