In 1971, biologists moved a small population of Italian ruin lizards (Podarcis sicula) from an island where they fed mainly on insects to a neighbouring island, Pod Mrčaru, where insects were scarce but tough, fibrous plants were highly abundant.
Within 36 years, researchers found that the lizards on Pod Mrčaru had evolved significantly larger heads, a stronger bite force, and specialized structures in their digestive tracts called cecal valves to ferment plant cellulose.
Use Charles Darwin's theory of natural selection to explain how the population of lizards on Pod Mrčaru evolved larger heads and a stronger bite force compared to the ancestral insect-eating population.
122 exam-style questions on OCR GCSE Biology 5.2 Natural selection and evolution, covering 5.2.1 Genetic variation within a population, 5.2.2 Developments in classification systems, 5.2.3 How evolution occurs through natural selection, 5.2.4 Evolution as change over time, 5.2.5 Evidence for evolution, and 5.2.6 Darwin and Wallace. Each one has a worked solution and a mark scheme showing where the marks go.