CIE IGCSE Biology

Revision Notes

18.5 Selective Breeding

Artificial Selection

  • Selective breeding means to select individuals with desirable characteristics and breed them together
  • The process doesn’t stop there though because it’s likely that not all of the offspring will show the characteristics you want so offspring that do show the desired characteristics are selected and bred together
  • This process has to be repeated for many successive generations before you can definitely say you have a ‘new breed’ which will reliably show those selected characteristics in all offspring
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Natural vs Artificial Selection

Natural vs Artificial Selection table, IGCSE & GCSE Biology revision notes

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Selectively Breeding Plants

  • Plants are selectively bred by humans for development of many characteristics, including:
    • disease resistance in food crops
    • increased crop yield
    • hardiness to weather conditions (e.g. drought tolerance)
    • better tasting fruits
    • large or unusual flowers
  • An example of a plant that has been selectively bred in multiple ways is wild brassica, which has given rise to cauliflower, cabbage, broccoli, brussel sprouts, kale and kohlrabi:

 

Selective breeding plants, IGCSE & GCSE Biology revision notesAn example of selective breeding in plants

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Selectively Breeding Animals

  • Selective breeding of animals has been carried out by humans for thousands of years
  • It takes place in the same way as selective breeding of plants
  • Individuals with the characteristics you want are bred together (often several different parents all with the desired characteristics are chosen so siblings do not have to be bred together in the next generation)
  • Offspring that show the desired characteristics are selected and bred together
  • This process is repeated for many successive generations before you can definitely say you have a ‘new breed’ which will reliably show those selected characteristics in all offspring
  • Animals are commonly selectively bred for various characteristics, including:
    • cows, goats and sheep that produce lots of milk or meat
    • chickens that lay large eggs
    • domestic dogs that have a gentle nature
    • sheep with good quality wool
    • horses with fine features and a very fast pace
  • An example of an animal that has been selectively bred by humans in many ways to produce breeds with many different characteristics is the domestic dog, all breeds of which are descended from wolves

 

Selective breeding dogs, IGCSE & GCSE Biology revision notesSelective breeding has produced many different breeds of domestic dog

Exam Tip

Make sure that you include the need to repeat the selective breeding for many generations in any exam answer you give – selecting two parents with desired characteristics, breeding them and stopping there is not selective breeding and will not give rise to a new breed.

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Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.
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