B6 Selective Breeding (page 77) Flashcards
What is Selective Breeding?
is when humans artificially select the plants or animals that are going to breed so that the genes for particular characteristics remain in the population.
(You take the best plants or animals and breed them together to get the best possible offspring).
Organisms are selectively bred to develop features that are useful or attractive, give some examples?
Animals that produce more meat or milk.
Crops with disease resistance.
Dogs with a good, gentle temperament
Decorative plants with big or unusual flowers.
Describe the basic process involved in selective breeding?
1) From your existing stock, select the ones which have the characteristics you’re after.
2) Breed them with each other
3) Select the best of the offspring, and breed them together.
4) Continue this process over several generations, and the desirable trait gets stronger and stronger.
Eventually all the offspring will have the characteristic.
There is also another name for Selective breeding, what is it?
Artificial selection.
In agriculture (farming), selective breeding can be used to improve yields, give examples?
(a yield is a measurement of the amount of a crop grown, or product such as wool, meat or milk produced, per unit area of land)
To improve meat yeilds, a farmer could breed together the cows and bulls with the best characteristics for producing meat. e.g. large size.
After doing this for several generations the farmer would get cows with a very high meat yield.
Is Selective Breeding a new thing we have been doing?
No Selective breeding is nothing new - people have been doing it for thousands of years. It’s how we ended up with edible crops from wild plants and how we got domesticated animals like cows and dogs.
What is the main problem with selective breeding?
It reduces the gene pool - the number of different alleles (forms of a gene) in a population. This is because the farmer keeps breeding from the “best” animals or plants - which are all closely related. This is known as inbreeding.
Inbreeding can cause health problems why?
because there’s more chance of the organisms inheriting harmful genetic defects when the gene pool is limited.
(some dog breeds are particulary susceptible to certain defects because of inbreeding - e.g. pugs often have breathing problems).
With Inbreeding, there can also be serious problems if a new disease appears, why?
because there’s not much variation in the population. All the stock are closely related to each other, so if one of them is going to be killed by a new disease, the others are also likely to succumb to it.
Tell me the flow-chart for Selective Breeding problems?
Selective Breeding»_space;»»»>
Reduction in the number of different alleles (forms of a gene)»_space;»»»»>
Less chance of any resistant alleles being present in the population
Give an example of different breeds of dog coming from selective breeding?
E.g. somebody thought ‘i really like this small, yappy wolf - I’ll breed it with this other one’, After thousands of generations, we got poodles.
Explain how you could selectively breed for floopy ears in rabbits (4 marks)
Select rabbits with floppy ears (1 mark) and make them breed together to produce offspring (1 mark). Select offspring with floppy ears and breed the together (1 mark) Repeat this over many generations until all of the offspring have floppy ears (1 mark).
What potential issues can selective breeding cause?
Selective breeding reduces the gene pool (1 mark). This causes an increased chance of organisms inheriting harmful genetic defects (1 mark). There is also an increased chance that a population could be wiped out by a new disease (1 mark)
