How do humans change species by selective breeding and tissue culture?
Explain selective breeding and its impact on food plants and domesticated animals, and describe the process of tissue culture and its advantages in research and plant breeding.
A focused answer to Edexcel GCSE Biology 4.8 and 4.9B, covering how selective breeding works and its impact on crops and livestock, and tissue culture and its uses in research and plant propagation.
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What this dot point is asking
Edexcel statements 4.8 and 4.9B want you to explain selective breeding (artificial selection) and its impact on food plants and domesticated animals, and to describe tissue culture (4.9B is Biology only) and why it is useful in research and plant breeding. The contrast with natural selection (humans choosing, not the environment) is key.
Selective breeding
The process is a repeated cycle:
- Choose the parents that best show the desired feature (for example the highest milk yield, the most disease-resistant wheat, or the gentlest temperament).
- Breed these chosen individuals together.
- From their offspring, select again those with the best version of the feature.
- Repeat over many generations, so the feature steadily improves.
The main disadvantage is reduced genetic variation. Repeatedly breeding similar, closely related individuals (inbreeding) means fewer different alleles in the population. This makes the breed more vulnerable to disease (one illness could affect them all) and more likely to inherit harmful recessive alleles from both parents, causing inherited health problems.
Tissue culture (Biology only)
To carry out plant tissue culture, a small piece of tissue is taken from a plant, sterilised, and placed on a growth medium containing nutrients and plant hormones, all kept free from microbes. The cells divide and differentiate to form tiny new plants, which can then be grown on.
The advantages of tissue culture are:
- It produces many identical copies quickly from a small amount of starting material.
- It can preserve and propagate rare or endangered plant species.
- It allows growers to reproduce a plant with exactly the desired features (since the copies are clones).
- In medical research, culturing cells lets scientists study cells and test substances without using whole organisms.
Try this
Q1. State why selective breeding can reduce the long-term health of a breed. [1 mark]
- Cue. It reduces genetic variation (inbreeding), making the breed more vulnerable to disease and inherited disorders.
Q2. Give two advantages of tissue culture for a plant grower. [2 marks]
- Cue. Any two of: many identical copies quickly, preservation of rare species, exact reproduction of desired features.
Exam-style practice questions
Practice questions written in the style of Pearson Edexcel exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Edexcel 20184 marksA farmer wants to produce cattle that give a high milk yield. Describe how the farmer could use selective breeding to do this.Show worked answer →
A 4-mark describe question rewards the repeated cycle of choosing and breeding.
- From the herd, choose the cattle with the highest milk yield (the desired characteristic).
- Breed these selected animals together.
- From the offspring, again choose those with the highest milk yield.
- Repeat this selection and breeding over many generations, so the average milk yield of the herd gradually increases.
Markers reward selecting the best individuals, breeding them, selecting from the offspring, and repeating over generations. Saying simply that the farmer picks good cows, without the repeated cycle, caps the marks.
Edexcel 20213 marksExplain one disadvantage of selective breeding for the long-term health of a breed.Show worked answer →
A 3-mark explain question rewards a reasoned disadvantage about reduced variation.
Selective breeding repeatedly breeds closely related individuals with the same desired feature, so the population loses genetic variation (inbreeding). This means there are fewer different alleles in the population.
With low variation, the breed is more vulnerable: a new disease could affect all of them, and harmful recessive alleles are more likely to be inherited from both parents, causing inherited health problems.
Markers reward reduced genetic variation (inbreeding) and a clear consequence (vulnerability to disease or inherited disorders). Naming a disadvantage with no explanation scores less.
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Sources & how we know this
- Pearson Edexcel GCSE (9-1) Biology (1BI0) specification — Pearson (2016)