Selective Breeding (Edexcel IGCSE Science (Double Award): Biology): Flashcards
Exam code: 4SD0
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Define selective breeding.
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Define selective breeding.
Selecting individuals with desirable characteristics and breeding them together. Also called artificial selection.
Describe the process of selective breeding.
Select individuals with the desired characteristics and breed them together.
Select the offspring that show those characteristics and breed those together.
Repeat for many successive generations, until all offspring reliably show the characteristics — a new breed.
Why must selective breeding be repeated over many generations?
Because not all offspring will show the desired characteristics. Only after many generations will they appear reliably in all offspring.
Name four characteristics plants are selectively bred for.
Disease resistance in food crops
Increased crop yield
Hardiness to weather conditions, such as drought tolerance
Better tasting fruits, or large or unusual flowers
Which crops have all been bred from wild brassica?
Cauliflower, cabbage, broccoli, Brussels sprouts, kale and kohlrabi.
Define inbreeding.
When only the 'best' animals or plants, which are closely related to each other, are bred together.
What does inbreeding do to the gene pool?
It causes a reduction in the gene pool — a reduction in the number of alleles present in the population.
Give two risks of a reduced gene pool.
An increased chance of inheriting harmful genetic defects
Greater vulnerability to new diseases, since resistant alleles are less likely to be present
Selective breeding is also known as ＿＿＿＿＿＿＿＿ selection.
Selective breeding is also known as artificial selection.
Breeding closely related individuals together is called ＿＿＿＿＿＿＿＿.
Breeding closely related individuals together is called inbreeding.
True or False?
Breeding two plants with a desired trait once creates a new breed.
False.
The process must be repeated for many successive generations before the characteristics appear reliably in all offspring.
True or False?
Inbreeding increases the number of alleles in a population.
False.
Inbreeding reduces the gene pool, so there are fewer alleles in the population.
Describe how animals are selectively bred.
Individuals with the desired characteristics are bred together.
Offspring showing those characteristics are selected and bred together.
The process is repeated for many successive generations.
Why are several different parents often chosen?
So that siblings do not have to be bred together in the next generation.
Name four characteristics animals are selectively bred for.
Cows, goats and sheep that produce lots of milk or meat
Chickens that lay large eggs
Sheep with good quality wool
Horses with fine features and a fast pace, or dogs with a gentle nature
Which animal best illustrates selective breeding, and from what?
The domestic dog. All breeds are descended from wolves.
Compare when natural and artificial selection occur.
Natural selection occurs naturally
Artificial selection only occurs when humans intervene
Compare the outcomes of natural and artificial selection.
Natural selection produces populations better adapted to their environment and survival
Artificial selection produces populations with features useful to humans, not necessarily useful to the individual's survival
Why is artificial selection faster than natural selection?
Because only individuals with the desired features are allowed to reproduce, whereas natural selection usually takes a long time.
All breeds of domestic dog are descended from ＿＿＿＿＿＿＿＿.
All breeds of domestic dog are descended from wolves.
Selective breeding must be repeated for many successive ＿＿＿＿＿＿＿＿ to create a new breed.
Selective breeding must be repeated for many successive generations to create a new breed.
True or False?
Selectively bred features always help the animal survive.
False.
Artificial selection produces features useful to humans, which are not necessarily useful to the individual's own survival.
True or False?
Artificial selection takes less time than natural selection.
True.
Only individuals with the desired features are allowed to reproduce, so change happens much faster.
Why is breeding two suitable parents once not selective breeding?
Because it will not give rise to a new breed — the process must be repeated over many generations.
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