We now know that in the vast majority of cases this type of inheritance…

The idea

This statement corrects an early idea about how characteristics pass from parents to offspring. Lamarck proposed that features acquired during an organism's life, such as a giraffe stretching its neck to reach high leaves, could be inherited by its young. We now understand that most body changes gained during life are not written into the gametes, so they are not passed on. Only changes to the DNA of gametes, such as new alleles formed by mutation, can be inherited. A stretched neck therefore does not make a longer-necked calf. The rare exceptions involve epigenetic marks or environmental effects on gametes, but these are not the main route of inheritance.

What earns the marks

• State that Lamarck's idea involved characteristics acquired during an organism's lifetime being passed to offspring.
• Explain that most acquired characteristics do not alter the DNA of gametes, so they cannot be inherited.
• Contrast this with inherited variation caused by mutations that produce new alleles in gametes.
• Use a correct example, such as a giraffe's stretched neck not being inherited, to show the idea is rejected.
• Recognise that inheritance depends on genetic material passed from parents to offspring, not on use or disuse of a body part.

Common mistakes and how to put them right

• Thinking that any feature an organism develops in life is automatically inherited.

  Put it right by stating that only changes in gamete DNA are normally inherited.

• Confusing Lamarck's idea with Darwin's natural selection.

  Put it right by noting that Darwin's mechanism selects existing inherited variation rather than creating it by use.

• Writing that acquired characteristics are never inherited in any circumstance.

  Put it right by saying they are not inherited in the vast majority of cases, leaving room for rare epigenetic effects.

Exam tips

• Link the statement to a named scientist, such as Lamarck, so the examiner sees the historical context.
• Use the phrase 'acquired characteristics' and explain why they are not usually passed on through gametes.
• If asked to compare, set out one clear difference between Lamarck's idea and natural selection rather than listing many vague points.