4.4 NATURAL
SELECTION
How did this happen?!
1. Why do we use selective breeding?
2. How did selective breeding make the cows so big?
Today’s aim
■ To outline a theory on natural selection
■ To be able to explain the difference between
natural selection and selective breeding
■ To look at Charles Darwin’s discoveries
How did giraffes get their long neck?
DISCLAIMER: this is just a theory.
We are not sure.
How did giraffes get their long neck?
How did giraffes get their long neck?
How did giraffes get their long neck?
How did giraffes get their long neck?
This is called
natural selection
Differences
Natural selection
Selective breeding
■ Species adapting in
response to natural
changes
■ Species changing due to
human control
Draw a flow chart
■ Draw pictures to complete the flow chart
■ It will compare selective breeding and natural
selection
■ Use page 53 in your coursebook to help you
Recap/warm up
Sometimes the DNA
doesn’t copy perfectly
and the new bacteria is
a tiny bit different
Discuss in pairs
Lichens
■ Lichens are weird
■ They aren’t plants, but they can photosynthesise
■ They don’t have roots to absorb water and nutrients
■ Can grow on almost any surface
■ Can even live INSIDE solid rock
■ Up to 6% of the EARTH’S SURFACE is covered in lichen
■ Some of the OLDEST LIVING THINGS in the world
Lichens
They’re really good at
absorbing things in the air.
What do you think they can
tell us?
Timeline
1849
Almost all
peppered
moths were
pale
Timeline
184
9
Almost all
peppered
moths were
pale
190
0
Near cities,
almost all
peppered
moths were
dark.
Why?
Timeline
184
9
Almost all
peppered
moths were
pale
Industrial
revolution
reduced air
quality.
Lichens died.
190
0
Near cities,
almost all
peppered
moths were
dark.
Why?
Timeline
184
9
Almost all
peppered
moths were
pale
Industrial
revolution
reduced air
quality.
Lichens died.
Pale
peppered
moths lost
their
camouflage
190
0
Near cities,
almost all
peppered
moths were
dark.
Why?
Timeline
184
9
Almost all
peppered
moths were
pale
Industrial
revolution
reduced air
quality.
Lichens died.
Birds could
see the pale
moths easily.
They ate
them.
Pale
peppered
moths lost
their
camouflage.
190
0
Near cities,
almost all
peppered
moths were
dark.
Why?
Timeline
184
9
Almost all
peppered
moths were
pale.
Industrial
revolution
reduced air
quality.
Lichens died.
Birds could
see the pale
moths easily.
They ate
them.
Pale
peppered
moths lost
their
camouflage.
Dark moths
were left to
reproduce.
190
0
Near cities,
almost all
peppered
moths were
dark.
Warm up
■ Look carefully at the
camel.
■ Write down 5 features
that make it a camel,
such as its hump.
■ Write down why you
think these features
would help it to survive
in the desert.
Who was Charles darwin?
Write down what you can remember
about the theory of evolution.
Galapagos islands
■ Use your map of the Galapagos islands,
information and pictures of the birds that live
there.
■ You have to figure out which bird lives where
and why.
Adaptations of animals
■ You and your partner will be given a picture
of an animal.
■ Think about it’s adaptations.
■ Write down how you think these features
help the animal survive.
Swap pictures and notes with the
next group along
■ Work together to mark the other group’s
work.
■ Think of at least one reason why their work
is good.
■ Think of at least one way you think their
work could be made better.
■ Swap back and read through your feedback.
Evolution happens through natural selection:
Members of the same species have genes
that are slightly different.
Individuals with genes most suited
to the environment are more likely
to survive and reproduce.
These genes are passed to the offspring
in the next generation.
Animals can become extinct when they
are not well adapted to their
environment.
Today’s aim
■ To outline a theory on natural selection
■ To be able to explain the difference between
natural selection and selective breeding
■ To look at Charles Darwin’s discoveries
Summary
■ Natural selection occurs when the individuals
in a species most suited to the environment
survive and reproduce
Summary
■ Individuals in a species that survive can
reproduce. They pass on their genes and the
species changes to be more like them