Selective Breeding

D. Crowley, 2007

Selective Breeding

To understand what selective breeding is, and how this is useful

Wednesday, April 19, 2023

Super Animals Look at the two chickens and the table of their features: -

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 Bibbyfemale bird

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

What features do you hope will be shown by the offspring?

Kendo male bird Bibbyfemale bird

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

Super AnimalsFeatures

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

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!

Kendo male bird Bibbyfemale bird

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?

Poodle 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

Poodle Labrador Labradoodle

+

+

Natural Selection Species gradually evolve by a process of natural selection

Individuals in a species show a wide variation (due to gene differences)

Individuals with inherited features best suited to their environment are most likely to survive and reproduce: passing on their genetic information to their offspring

Over time, a species can change its appearance, and may even become a new species, unable to reproduce successfully with individuals of the original species

Individuals with the most favourable genes for the environment they live in are selected over time: this is natural selection

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

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

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.

Selective Breeding Worksheet

Stick in the worksheet and answer the questions

1. Balwen mountain: able to live in cold conditionsBluefaced Leicester: good quality woolPolled Dorset: good quality meatFriesian: produces lots of milk

2. Polled Dorset & Bluefaced Leicester3. Bluefaced Leicester & Balwen mountain4. Ram5. He only kept the offspring with the desirable characteristics,

which he allowed to breed - taking eight years to get the desirable traits

6. Sheep only breed every year, so it takes a long time for characterisitcs to become exaggerated enough to win a prize!

7. Not particulary hardy, but should be well tempered (so it can be easily herded); have good wool / meat / produce lots of milk etc…