Transcript Selective Breeding - This is Worley Science

Selective Breeding
Noadswood Science, 2012
Labradoodle
 Look at the following dogs - crossing a Poodle and a Labrador
results in a ‘Labradoodle’
 What features has the Labradoodle inherited from the Labrador?
 What features has the Labradoodle inherited from the Poodle?
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Poodle
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Labrador
Labradoodle
Labradoodle
 The Labradoodle is large (like the Labrador), has a fluffy coat
(like the Poodle) which sheds much less than a Labrador’s coat.
They are also generally well tempered and good swimmers (like
both its parents breeds).
 So the Labradoodle has favourable characteristics from both of
its parents breeds
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Poodle
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Labrador
Labradoodle
Selective Breeding
 Selective breeding is a process used to produce different breeds
of animals or varieties of plants that have useful
characteristics
 Using selective breeding you can produce a specific offspring
with useful characteristics of both parents
 What organisms do farmers ‘selectively breed’?
Selective Breeding
 Farmers can choose individual cows to mate in order to produce
a generation of cows that will yield more milk
 Farmers could also selectively breed for docile animals
 Apple growers want to produce a type of apple that is tasty and
resistant to disease. This can be done by crossing a type of
apple known for taste with another type that shows strong
resistance to disease
 Farmers could also selectively breed for crops of a uniform
height / when they are ready for harvest
E.g. Cows
 Suppose you wanted a variety of cow that produced a lot of
milk: 
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Choose or select the cows in your herd that produce the most milk
Only let these cows reproduce
Select the offspring that produce the most milk
Only let these offspring reproduce
Keep repeating the process of selection and breeding until you
achieve your goal
Animals
 To selectively breed animals, often a ‘stud’ male is used to
breed.
 Artificial insemination is also used (where a vet will deliberately
introduce semen into the female)
Summary
 The key is to identify the feature you want, and only breed from
the individuals that have that feature – it is achieved by…
 Select parents with the desired traits (things you want)
 Cross the parents (breed them)
 Select from the offspring
 Repeat (over many generations)…
 Selective breeding is used to:  Choose characteristics of the food item required
 Produce a more uniform crop (size / harvest time)
 Extend the tolerance range of an organism