Two isolated populations of birds have become different in size and feather colour. Researchers bring healthy adults from the populations together under suitable breeding conditions.
Which result gives the strongest evidence that the populations are now different species?
The adults mate successfully, and their offspring are fertile but intermediate in size.
The adults mate successfully, and their offspring are fertile but different in colour.
The adults mate successfully, and their offspring survive but cannot produce young.
The adults mate successfully, and their offspring survive but prefer different foods.
44 exam-style questions on AQA GCSE Biology 6.2 Variation and evolution, covering 6.2.1 Variation, 6.2.2 Evolution, 6.2.3 Selective breeding, 6.2.4 Genetic engineering, and 6.2.5 Cloning. Each one has a worked solution and a mark scheme showing where the marks go.