Selective breeding Cambridge IGCSE Co-ordinated Sciences (9–1) revision
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In plain words
Every breed of dog, from a Great Dane to a chihuahua, came from wolves. People did it by choosing which animals to breed: pick the two with the feature you like, breed them, pick the best of their young, and repeat for many generations.
Three things to know
- Selective breeding (artificial selection): humans choose individuals with the features they want, breed them together, choose the best of the offspring, and repeat over many generations.
- It has given us cows that make more milk, wheat with bigger grains and crops that resist disease.
- The drawback is less variation: the animals or plants become so alike that one disease could wipe them all out, and inbreeding can bring health problems.
Tips and tricks
- Four steps: select, breed, select the best offspring, repeat for many generations. "Many generations" is a mark.
- Selective breeding is not genetic modification. No genes are moved in a lab.
It lands in your notebook with its questions as flashcards.
Selective breeding: 5 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
Who decides which individuals breed in selective breeding?
That is what makes it artificial selection.
What is a disadvantage of selective breeding?
A population that is all alike can all catch the same disease.
How long does selective breeding take to change a population?
The selection has to be repeated again and again.
Which is an example of selective breeding?
Humans chose which plants to grow seed from.
What is the first step in selective breeding?
Then they are bred together.
Quiz
5 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
3 questions, 8 marks. Write your answers on paper, then check them.
Selective breeding
Cambridge IGCSE Co-ordinated Sciences (9–1) 0973 · 8 marks · papermunch.org
Name ______________________________ Date ______________
Describe how a farmer could use selective breeding to produce cows that give more milk.[4]
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Choose the cows that give the most milk and breed them with a bull from a high-yielding mother. Choose the offspring that give the most milk and breed them. Repeat this over many generations.
Give two features that plant breeders might select for in a crop.[2]
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Any two: higher yield; resistance to disease or pests; faster growth; better flavour; tolerance of drought.
Explain one disadvantage of selective breeding.[2]
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It reduces variation (the gene pool), so the whole population may be vulnerable to the same disease; or inbreeding can cause inherited health problems.
Answers: Selective breeding
- 1. Choose the cows that give the most milk and breed them with a bull from a high-yielding mother. Choose the offspring that give the most milk and breed them. Repeat this over many generations.
- 2. Any two: higher yield; resistance to disease or pests; faster growth; better flavour; tolerance of drought.
- 3. It reduces variation (the gene pool), so the whole population may be vulnerable to the same disease; or inbreeding can cause inherited health problems.