Inheritance and variation — Science, 11–13 years
Offspring receive genetic information from their parents, but they are not exact copies. Inherited differences and differences shaped by the environment help explain why members of one species resemble one another yet vary.
What inheritance means
Inheritance is the passing of genetic information from parents to offspring. This information helps build features such as blood group, eye colour or a plant's flower colour. Variation means individuals of the same species have differences; some come from genes, some from the environment, and many come from both.
Why study differences?
Farmers and breeders noticed that parents often resemble their offspring, yet useful traits could appear in different amounts. Scientists needed a way to explain both patterns without claiming that every feature is fixed by one parent. Studying inheritance helps us understand family resemblances, genetic conditions and how populations can change over generations.
A flower-colour example
Suppose a plant has one gene version for purple flowers from each parent, written P and P. Step 1: each parent passes one version to the seed. Step 2: the seed receives P from both, so its pair is PP. Step 3: the plant grows purple flowers. This predicts one genetic possibility; sunlight, soil and water can still affect how well the plant grows.
Genes are not the whole story
A reasonable mistake is to think that every visible feature must come entirely from genes, because family traits are easy to notice. Height shows why this is incomplete: genes influence the possible range, while nutrition and health also matter. Other features, such as a scar or a suntan, are not passed to children through genes.
Inheritance in the world
Doctors use inheritance patterns to estimate the chance of some genetic conditions, while counsellors help families understand what a result can and cannot show. Plant and animal breeders select inherited traits such as disease resistance. DNA evidence can also help identify people, but a genetic result is evidence about likelihood, not a complete description of a person.
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