AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Variation: a combination of genes and the environment.
Variation between individuals comes from two sources working together: the genes they inherit and the environment they experience.
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Variation between individuals comes from two sources working together: the genes they inherit and the environment they experience. Genes are lengths of DNA passed from parents in gametes, so offspring inherit alleles that set features such as blood group, eye colour and the potential height a person could reach. Environment covers everything an organism encounters after fertilisation, including diet, exercise, sunlight, accidents and upbringing. Many features, such as height, mass and skin tone, are affected by both, so the observed value is not fixed by genes alone. For example, a child may inherit alleles for tall stature but a poor diet can prevent that potential being reached. Similarly, two identical plant cuttings grown with different light and mineral levels end up different sizes.
What earns the marks
- State that genes are inherited from parents and carry the instructions for features.
- State that the environment includes factors such as diet, exercise, light and accidents.
- Explain that many characteristics are controlled by both genes and environment, not one alone.
- Use a named example, such as height or plant growth, to show how both factors combine.
- Distinguish inherited features from those changed mainly by environmental factors.
Common mistakes and how to put them right
Saying a feature is caused only by genes or only by the environment.
Put it right by stating that most features result from both acting together.
Confusing the environment with 'the surroundings' only.
Put it right by including diet, exercise, disease and other lifestyle factors.
Writing that genes change during life to match the environment.
Put it right by stating that gene alleles are inherited and do not change, but gene expression and growth can be affected.
Exam tips
- Name the feature first, then say how genes and environment each affect it.
- Use the phrase 'combination of genes and the environment' when explaining mixed features.
- Give one clear example rather than several vague ones to secure the explanation.
Try the lesson
The start of the Variation: a combination of genes and the environment. lesson, made from checked teaching notes for this specification point.
Have a go first
A student says that a person's height is caused only by the genes they inherit. Which statement best describes the actual cause of variation in human height?
Listen
Variation between individuals comes from two sources working together: the genes they inherit and the environment they experience. Genes are lengths of DNA passed from parents in gametes, so offspring inherit alleles that set features such as blood group, eye colour and the potential height a person could reach. Environment covers everything an organism encounters after fertilisation, including diet, exercise, sunlight, accidents and upbringing. Many features, such as height, mass and skin tone, are affected by both, so the observed value is not fixed by genes alone. For example, a child may inherit alleles for tall stature but a poor diet can prevent that potential being reached. Similarly, two identical plant cuttings grown with different light and mineral levels end up different sizes. A strong answer earns marks for these points. State that genes are inherited from parents and carry the instructions for features. State that the environment includes factors such as diet, exercise, light and accidents. Explain that many characteristics are controlled by both genes and environment, not one alone. Use a named example, such as height or plant growth, to show how both factors combine. A common slip: Saying a feature is caused only by genes or only by the environment. Instead, stating that most features result from both acting together. Exam tip: Name the feature first, then say how genes and environment each affect it.
Key words
Say what each word means before you turn the card.
genes
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environment
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variation
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combination of genes and the environment
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See every definition
- genes
- Lengths of DNA passed from parents in gametes, so offspring inherit alleles that set features.
- environment
- Everything an organism encounters after fertilisation, including diet, exercise, sunlight, accidents and upbringing.
- variation
- Differences between individuals that come from two sources working together: the genes they inherit and the environment they experience.
- combination of genes and the environment
- The way many features, such as height, mass and skin tone, are affected by both, so the observed value is not fixed by genes alone.
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