2.5 Variation and Natural Selection
Continuous and discontinuous variation, genetic and environmental causes, natural selection, evolution, extinction and selective breeding.
How to study for CCEA GCSE Biology
Learn each process as a structure-and-mechanism chain, use data with units, and prepare every prescribed practical from planning through conclusion and evaluation.
Core concepts
Concept 1
Continuous variation spans a range and is displayed with a histogram, while discontinuous categories are displayed with separated bars.
Exam cue: Choose a graph from the type of data, not from which graph is easiest to draw.
Concept 2
Phenotype can reflect genetic variation from mutation and sexual reproduction, environmental influences, or their interaction.
Exam cue: Explain selection as a multi-generation change in a population, not an individual changing because it needs to.
Concept 3
Natural selection changes allele representation because inherited variants affect survival and reproduction, while selective breeding applies human choice.
Exam cue: Distinguish the selective pressure, inherited variation and reproductive consequence.
Risk pitfalls and guardrails
Saying organisms develop helpful mutations in response to the environment.
Guardrail: Do not import an England board, Single Award or Double Award structure, and do not replace a biological mechanism with a vague purpose statement.
Using a bar chart with touching bars for continuous data.
Guardrail: Do not import an England board, Single Award or Double Award structure, and do not replace a biological mechanism with a vague purpose statement.
Treating selective breeding and genetic engineering as the same process.
Guardrail: Do not import an England board, Single Award or Double Award structure, and do not replace a biological mechanism with a vague purpose statement.
Memory anchors
Continuous variation
A measured characteristic with values across a range and no fixed categories.
Discontinuous variation
A characteristic placed into distinct categories.
Mutation
A random change in chromosome number or gene structure.
Natural selection
Differential survival and reproduction of organisms with inherited variation.
Evolution
Change in inherited characteristics of a population over generations.
Selective breeding
Human selection of parents with desired characteristics over generations.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
Which characteristic shows continuous variation?
Which characteristic shows discontinuous variation?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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