Download Growth and Development

New Genes For Old
Part 1
Learning Objectives
• To learn how plants and animals can be
changed by selective breeding.
• To learn about the advantages and
disadvantages of selective breeding.
• To learn about the problems with small
gene pools.
Success Criteria
• I can state why selective breeding is
important.
• I can describe the stages involved in
selective breeding.
• I can state 2 major problems with involved
with inbreeding in selective breeding.
Starter
Why are the following organisms important to humans?
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•
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Milk
Butter
Meat
Fertiliser
Manure used
for energy
• Works on farms
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Good pet
Loyal
Brave
Working dog
Security
Police use
Drug sniffing
Starter
What is the link between these animals?
All of the
breeds of
dog are
descende
d from
WOLVES!
SELECTIVE BREEDING
Selective Breeding
• None of the following organisms would be around
today without the help of humans.
• Farmers choose animals and plants with the best
characteristics.
• They then breed them to produce offspring that have
those characteristics too.
Selective Breeding
Todays cows have huge udders
because farmers have selected and
bred cows that produce lots of milk.
In fact, modern cows would be in
pain or even die if not milked.
Dogs are only around because humans
domesticated wolves thousands of years ago.
Over time, breeding for particular
characteristics has led to all the breeds we see
today.
Selective Breeding: Cows
Jersey cows produce milk that is rich in
cream, but there isn’t much of it.
Friesian cows produce lots of milk, but
it isn’t very creamy.
What could be done in order to
produce lots of creamy milk?
Cross-breed a Jersey
cow with a Friesian bull
Cross-breed a Friesian
cow with a Jersey bull
Choose the best the
offspring that produce
high-quantity, creamy
milk.
Repeat this for many
generations.
Questions
1. Why would farmers want to plant wheat crops that
grow quickly?
2. Why do farmers want pigs that produce lots of baby
piglets?
3. Name one characteristic of strawberry plants that
would be useful to gardeners.
4. Describe how a farmer could produce a plant with
large, sweet strawberries, if she starts with a plant
that has small, sweet berries and one with large,
non-sweet berries.
Answers
1. To produce a higher yield and therefore make more
money.
2. To make a greater profit off each female pig (sow), as
piglets can be sold. Would also mean more meat
production, hence greater profit.
3. Disease-resistance. Sweet-tasting. Fast-growing.
4. Breed the two plants together. Choose the plants
that produce the largest, sweetest berries and then
keep breeding for many generations.
Selective Breeding: Dogs
• There are over 300 breeds of dogs in the world.
Strong dogs
Clever dogs
Stupid dogs
• All are the same species and only exist because of
selective breeding by humans.
• Their characteristics have been selected for over
hundreds of generations.
• COMPLETE WORKSHEET 1: “DOG BREEDING”
Answers in folder:
Collins B3g1
lesson file.
Problems with Selective Breeding
• As you’ve probably noticed, selective breeding
involves mating animals that are closely related.
• This is called inbreeding.
• It can lead to lots of health problems within a
species.
Bulldogs have been bred with
large folds of skin on their
faces.
This is a recessive characteristic
that affects their sight.
Suggest reasons why bulldogs
would not survive in the wild…
HIGHER
Inbreeding
• The inbreeding involved in selective breeding causes
a reduction in the gene pool.
• This means there are fewer types of alleles.
With fewer alleles, animals
and crops are more likely
to die of disease.
The sheep on the right has
deformities due to
generations of inbreeding,
causes vital genes to be
lost from the population.
PLENARY
Plenary
• Produce a comic strip depicting the stages involved in
the selective breeding of large sheep with a lot of
wool.
• Start with:
- Large male sheep (not much wool)
- Average sized female (lots of wool)
Learning Objectives
• To learn how plants and animals can be
changed by selective breeding.
• To learn about the advantages and
disadvantages of selective breeding.
• To learn about the problems with small
gene pools.
Success Criteria
• I can state why selective breeding is
important.
• I can describe the stages involved in
selective breeding.
• I can state 2 major problems with involved
with inbreeding in selective breeding.