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Selective Breeding D. Crowley, 2007
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Wednesday, September 19, 2018Wednesday, September 19, 2018
Selective Breeding To understand what selective breeding is, and how this is useful
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Behaviour with other hens
Super Animals Imagine you work for the super-chick egg company, and it has been decided the Kendo and Bibby have been chosen to mate Research suggests the following: - Supermarkets want large eggs which are brown with yellow yolks Farmers want passive livestock which are healthy Features Kendo family Bibby family No. eggs per week 6 4 Colour of eggs White Brown Size of eggs Medium Large Colour of yolk Bright yellow Pale lemon Resistance to disease Highly resistant Not resistant Behaviour with other hens Aggressive Not aggressive Kendo male bird Bibby female bird What features do you hope will be shown by the offspring?
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Behaviour with other hens
Super Animals Features Kendo family Bibby family No. eggs per week 6 4 Colour of eggs White Brown Size of eggs Medium Large Colour of yolk Bright yellow Pale lemon Resistance to disease Highly resistant Not resistant Behaviour with other hens Aggressive Not aggressive Kendo male bird Bibby female bird You will want the following: - 6 eggs Brown eggs Large eggs Bright yellow yolk Highly resistant Not aggressive However there are no guarantees this is the animal you will produce!
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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? + Labradoodle Poodle + Labrador
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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 + Labradoodle Poodle + Labrador
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E.g. Cows Suppose you wanted a variety of cow that produced a lot of milk: - 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
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Selective Breeding vs. Natural Selection
Traits chosen by humans Traits that are most preferred or useful are passed on New species/varieties are produced by combining two individuals with desired traits Change in population can happen quickly Traits “selected” by environment Traits that are advantage for survival are passed on New species/varieties evolve as those with traits produce more offspring in the population Change in population is usually very slow; takes many generations
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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 Farmers can choose individual cows to mate in order to produce a generation of cows that will yield more milk Apple growers want to produce a type of apple that is tasty and resistant to disease. This can be done by crossing a variety of apple known for taste with another variety that shows strong resistance to disease
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Summary The key is to identify the feature you want, and only breed from the individuals that have that feature. Examples of what selective breeding can produce include: - Hens that lay big eggs of a particular colour Cattle that produce lots of meat Tomato plants that produce lots of tomatoes Crops that are resistant to certain plant diseases.
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