Evolution — AQA GCSE Biology
Test yourself on Evolution with AQA GCSE practice questions.
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Evolution explained
Evolution is a change in the inherited characteristics of a population over time through natural selection, and it may lead to a new species.
Read the full explanation
The mechanism starts with genetic variation from mutation and sexual reproduction. Individuals whose characteristics suit the environment survive, reproduce and pass on their alleles, so allele frequencies change over generations. A population is all the organisms of one species in a habitat, so evolution is measured in populations, not individuals. If populations become so different, or are separated so they can no longer interbreed to produce fertile offspring, a new species may form. A method is to write the chain: variation, selection pressure, survival and reproduction, inheritance, allele frequency change, possible new species.
Your focus
- Define evolution as a change in the inherited characteristics of a population over time.
- Describe natural selection as the process that causes evolution.
- Explain how reproductive isolation can lead to the formation of a new species.
Evolution exam tips
Marking Points
- Evolution is a change in the inherited characteristics of a population over time.
- The mechanism is natural selection acting on genetic variation within the population.
- Individuals with advantageous alleles survive, reproduce and pass those alleles to offspring.
- Allele frequencies in the population change over many generations.
- If populations become reproductively isolated and can no longer produce fertile offspring, a new species may form.
Examiner Tips
- 💡Include the words population and over time in any definition of evolution.
- 💡Explain natural selection as a sequence of variation, selection, reproduction and inheritance.
- 💡State that a new species forms only if populations can no longer interbreed to produce fertile offspring.
Common Mistakes
- Defining evolution as an individual organism changing during its lifetime: correct this by defining it as a change in a population over generations.
- Saying organisms evolve because they want to survive: correct this by stating that variation is random and selection is non-random.
- Treating evolution and natural selection as identical: correct this by describing natural selection as the process and evolution as the change in inherited characteristics over time.