Natural Selection and Genetic Modification – 6

Year 9 Topic 3: Natural Selection and Genetic Modification

Learning Opportunity 6: Selective Breeding

This Learning Opportunity has 6 tasks.

Target Time: 60

By the end of this learning opportunity you will be able to:

Describe some features of animals and plants that breeders would want to selectively breed for. 

Explain selective breeding and its impact on food plants and domesticated animals.

Evaluate the benefits and risks of selective breeding in modern agriculture and medicine, including practical and ethical implications.

Key words: Characteristic, desirable, breed.

Task 1: Name 5 breeds of dog. Why might some people want a cross breed of dog such as a Labradoodle? Click on the link below if you are unsure.

https://www.pets4homes.co.uk/dog-breeds/labradoodle/

Task 2: Fill in the text below using the key words.

Reproduce, similar, variety, selecting, breed, desirable, characteristic.

Selective breeding involves ………………………. organisms based on desirable ………………………………. and ensuring these ………… together to have offspring with this ……………………. characteristic. These offspring are then selected based on the ………………….. characteristic and this is repeated again so that a new …………….. of animal or ……………….. of plant occurs.  

Answers are available at the end of this learning opportunity.

Task 3: Desirable characteristics are ones that would typically benefit humans in some way. Answer the questions below.

  1. What might a dairy cow breeder select as the desirable characteristics for their cows? 

2. How might ‘sausage’ dachshund dogs have been bred to be so small and long? 

3. Selectively breeding plants has happened for 1200 years, what might tomato plant farmers selectively breed for in their plants? (name 3 characteristics) 

Answers are available at the end of this learning opportunity.

Task 4: Watch the video. Summarise the arguments for and against selectively breeding pugs to have certain characteristics. Include ethical issues as well as scientific ones. Use the table to write your summary.

Arguments for selectively breeding   Disadvantages for selectively breeding 
              






 

Task 5: Read the information below then answer the question.

Variation in animals and plants and within these species and breed is important. Where selective breeding occurs, only certain alleles and phenotypes are selected and therefore others become rarer. These rarer alleles may have been useful to the species and can end up being ‘lost’ or bred out of the species as they no longer have these.  

What would happen to variation if all animals and plants were selectively bred?

Task 2 Answers

Selective breeding involves selecting organisms based on desirable characteristics and ensuring these reproduce together to have offspring with this desirable characteristic. These offspring are then selected based on the similar characteristic and this is repeated again so that a new breed of animal or variety of plant occurs.  

Task 3 Answers
  1. Examples: high milk yield, mild temperament, resistance to disease.
  2. Breeding two dogs with long bodies and short legs. Then selecting the offspring with the longest bodies and shortest legs to reproduce with others who share these desirable characteristics. This process would have been repeated until the breeder was satisfied with the length and size of the offspring.
  3. Examples: colour, increased nutritional content, shape.
Task 5 Answers

If all animals and plants were selectively bred, variation would be greatly reduced. The gene pools (genes and their different alleles) within each species would decrease due to the selective breeding focus on certain desirable characteristics.

Task 6: Complete the exam question.

Q1. * The picture shows two varieties of potato plant. 

New varieties of potato plant can be produced by selective breeding. 

Explain how selective breeding of the two varieties of potato plants can produce new potato plants that are all faster growing and produce many, large potatoes. (6) 

This is a 6 mark question so you need to reflect on;  

  • The command word 
  • What plan you need to draft before writing your answer 
  • Your answer needs to be a large paragraph (at least 6 lines) including keywords from the lesson 
Mark scheme – mark your answer

Q1. 
  

If you would like to learn more about the topics covered in this learning opportunity then follow the link below!

https://www.bbc.co.uk/bitesize/guides/zy7vw6f/revision/5

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