Transcript Natural selection in rats

Natural Selection
L.O: To understand how natural
selection can lead to evolution
Natural Selection – Match each statement to
its title and put them in order.
1 All living things in a species
are not the same.
A. Competition
2 There is not enough food or
space for all of them.
B. Survival
3 Some individuals have
features which help them
survive.
C. Variation
4 They are more likely to have
offspring. More of the next
generation have the useful
feature.
D. Reproduction
Natural Selection
1) Each species shows variation:
Get off
my land
2) There is competition within each
species for food, living space,
water, mates etc
3) The “better adapted” members of
these species are more likely to
survive – “Survival of the Fittest”
Gutted!
Yum
4) These survivors will pass on their
better genes to their offspring who
will also show this beneficial variation.
A smaller example…
Consider the four steps of natural selection in the example of
some bacteria that has become resistant to penicillin:
Bacteria
1) Variation – some strains of bacteria
are resistant and some aren’t.
2) Competition – The non-resistant
bacteria are killed by the penicillin.
3) Survival of the fittest – the
resistant bacteria survive.
Penicillin
4) Passing on of genes – the resistant
bacteria reproduce and pass on
their adaptations to their
offspring.
Natural Selection
If an animal or plant has an advantage in
competition against other members of its
species it is more likely to survive and
breed (“survival of the fittest”).
Mutations
• Each gene is the
instruction for making
one protein.
• Sometimes a mistake
is made when the
gene’s DNA is copied.
• The gene may code for
a different protein.
• Mutations do happen
naturally.
• They can also be
caused by some
chemicals, and ionizing
radiation.
Explain what a mutation is and how it can occur.
Back
How can mutations be helpful?
• Most mutations do not help the organism.
• The different protein that is made cannot do its job
well.
This bacterium is resistant to
most antibiotics.
• But mutations are random – a very small number
may help the organism survive in some
environments.
• For example, some bacteria have mutations that
make them resistant to certain antibiotics.
• Sickle-cell anaemia is a serious blood disease.
People with two copies of the disease allele can be
very ill. But people who carry just one copy of the
allele have protection from malaria. This helps them
to survive in countries where malaria is common.
A person who is a carrier of
the sickle cell allele is
protected from malaria.
Back
Mutations True or False
1. A mutation is a change in the DNA
2. Mutations are useful most of the time
3. Mutations can cause cancer to develop if a mutation
occurs in a gamete
4. Mutations can cause the young to die or develop
abnormally if a mutation occurs within a gamete
5. All individuals which have a mutation have an
advantage over other individuals, and lead to natural
selection
6. The chance of a mutation can be increased by
exposure to ionising radiation such as UV, X-rays and
radioactive substances
7. Certain chemicals can increase the chance of a
mutation
Natural Selection – The
Peppered Moth
Natural Selection – The
Peppered Moth
Natural Selection
and the Peppered
Moth
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2.
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8.
Cut 10 small pieces of white and 10 pieces of black
paper.
Place them on a large piece of black paper.
Cover your eyes with a scarf or jumper so you can
just see through (this is more realistic as predators
don’t have eyesight as good as us).
Pick off 10 pieces of paper (the ones easiest to find).
Draw a table with the number of black surviving in
one column and number of white in the other.
Record how many black and white you have.
Add this number of black and white pieces of paper
demonstrating reproduction.
Repeat until you have all of one colour.
Write a conclusion.
Natural selection in rats: warfarin
Now put these statements in the correct order.
A: The mutated gene is passed on and
is common in the rat population.
F:The resistant rats have a better
chance of surviving and reproducing.
B: A mutation in a rat’s sex cells make
its offspring resistant to warfarin.
G:People use warfarin to kill the rats.
C: The number of resistant rats
increases with each generation.
H: The resistant rats breed and pass
their features on.
D: Warfarin kills most rats.
I: Mutations are a change in the
genetic code.
E: Mutations may happen when DNA is
copied in the cell.
J: Mutations can be caused by some
chemicals or ionizing radiation.
Natural selection in rats: warfarin
Now put these statements in the correct order.
G:People use warfarin to kill the rats.
D: Warfarin kills most rats.
E: Mutations may happen when DNA is
copied in the cell.
J: Mutations can be caused by some
chemicals or ionizing radiation.
I: Mutations are a change in the
genetic code.
F:The resistant rats have a better
chance of surviving and reproducing.
H: The resistant rats breed and pass
their features on.
B: A mutation in a rat’s sex cells make
its offspring resistant to warfarin.
A: The mutated gene is passed on and
is common in the rat population.
C: The number of resistant rats
increases with each generation.