Selective Breeding

Selective Breeding Noadswood Science, 2012

Selective Breeding • What do you understand by the term ‘selective breeding’?

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

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

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

Natural Selection • 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 • 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 variety of apple known for taste with another variety that shows strongresistance 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: - • 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

Perfect Pet • Imagine you wanted to create your perfect dog – how would you selectively breed for it? • What two parents are you going to choose? • What qualities do each of them have (which you want) • How are you going to ‘get’ these qualities in your pet? • Draw out and annotate creating your perfect dog…

Dog Parents

Selective Breeding