Percentile Charts and Growth

This lesson covers how growth is measured and interpreted using percentile charts, as required by the Edexcel GCSE Combined Science specification (1SC0). You need to understand how growth data is collected, what percentile charts show and how to interpret them.

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Measuring Growth

Growth in organisms can be measured in several ways:

Measurement	Description	Advantage	Disadvantage
Length/height	Measuring the length or height of the organism	Quick and easy; non-destructive	Does not account for changes in mass
Wet mass	Mass of organism including water	Quick to measure	Varies with water content (e.g. after eating or drinking)
Dry mass	Mass of organism after all water removed	Most accurate measure of growth	Destructive — organism must be killed and dried

For humans, growth is most commonly measured using height and mass at regular intervals.

Exam Tip: If asked which measurement of growth is the most accurate, say dry mass. But always mention the disadvantage — it requires killing the organism, so it cannot be used for humans or to track the same individual over time.