AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Students should be able to explain how evolution occurs through natural…
Full specification wording
Evolution: Students should be able to explain how evolution occurs through natural selection of variants that give rise to phenotypes best suited to their environment.
Evolution happens when individuals in a population vary because of differences in alleles.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 3 of 4
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Evolution happens when individuals in a population vary because of differences in alleles. Some variants produce phenotypes better suited to the environment, for example longer necks reaching food or camouflage avoiding predators. These individuals are more likely to survive, compete successfully and reproduce, passing their alleles to offspring. Over many generations, the beneficial alleles become more frequent in the population, so the phenotype of the population changes. This is natural selection. The environment selects variants; it does not create them. For example, in a changing habitat, variants with thicker fur may survive cold better and leave more offspring, so thicker fur becomes common. Explaining the full chain from variation to allele frequency change is the skill assessed.
What earns the marks
- Variation exists within a population because of differences in alleles.
- Some variants give phenotypes better suited to the environment, improving survival and reproduction.
- Individuals with advantageous phenotypes are more likely to survive and pass on their alleles.
- Over generations, the frequency of advantageous alleles in the population increases.
- The environment selects existing variants; it does not cause new beneficial mutations on demand.
Common mistakes and how to put them right
Saying organisms adapt during their lifetime to suit the environment.
Put it right: Variants already exist and selection acts on them across generations.
Writing that the environment creates the needed mutation.
Put it right: Mutations arise randomly, and selection favours beneficial phenotypes.
Describing only survival without reproduction.
Put it right: Passing on alleles to offspring is essential for evolution.
Exam tips
- Write the explanation as a sequence: variation, selection, survival, reproduction, allele frequency change.
- Use a named example, such as antibiotic resistance in bacteria, to make the mechanism concrete.
- Avoid teleological wording such as 'trying to adapt'; describe selection of existing variants instead.
Try the lesson
The start of the Evolution: Students should be able to explain how evolution occurs through natural selection of variants that give rise to phenotypes best suited to their environment. lesson, made from checked teaching notes for this specification point.
Have a go first
In natural selection, which variants are most likely to survive and reproduce?
Listen
Evolution happens when individuals in a population vary because of differences in alleles. Some variants produce phenotypes better suited to the environment, for example longer necks reaching food or camouflage avoiding predators. These individuals are more likely to survive, compete successfully and reproduce, passing their alleles to offspring. Over many generations, the beneficial alleles become more frequent in the population, so the phenotype of the population changes. This is natural selection. The environment selects variants; it does not create them. For example, in a changing habitat, variants with thicker fur may survive cold better and leave more offspring, so thicker fur becomes common. Explaining the full chain from variation to allele frequency change is the skill assessed. A strong answer earns marks for these points. Variation exists within a population because of differences in alleles. Some variants give phenotypes better suited to the environment, improving survival and reproduction. Individuals with advantageous phenotypes are more likely to survive and pass on their alleles. Over generations, the frequency of advantageous alleles in the population increases. A common slip: Saying organisms adapt during their lifetime to suit the environment. Instead, variants already exist and selection acts on them across generations. Exam tip: Write the explanation as a sequence: variation, selection, survival, reproduction, allele frequency change.
Key words
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Variation
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Natural selection
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Differential survival and reproduction
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Allele frequency change
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See every definition
- Variation
- Differences in alleles within a population mean that individuals vary.
- Natural selection
- The environment selects existing variants, so beneficial alleles become more frequent over many generations.
- Differential survival and reproduction
- Individuals with advantageous phenotypes are more likely to survive and pass on their alleles to offspring.
- Allele frequency change
- Over generations, the frequency of advantageous alleles in the population increases.
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