This question is about the history of evolutionary theory and the development of life on Earth.
What is meant by the biological term natural selection?
Describe the work of Charles Darwin on the Galapagos Islands which led him to develop his theory of evolution by natural selection.
For the first billion years of life on Earth, photosynthetic organisms relied on hydrogen sulfide (H2SH_2SH2S) as an electron donor in anoxygenic photosynthesis:
carbon dioxide+hydrogen sulfide⟶glucose+sulfur+water \text{carbon dioxide} + \text{hydrogen sulfide} \longrightarrow \text{glucose} + \text{sulfur} + \text{water} carbon dioxide+hydrogen sulfide⟶glucose+sulfur+waterFollowing the evolution of oxygenic photosynthesis, water (H2OH_2OH2O) was used instead:
carbon dioxide+water⟶glucose+oxygen \text{carbon dioxide} + \text{water} \longrightarrow \text{glucose} + \text{oxygen} carbon dioxide+water⟶glucose+oxygenExplain why the transition from anoxygenic photosynthesis to oxygenic photosynthesis allowed primary producers to multiply and diversify dramatically, and how this enabled the evolution of complex, multicellular aerobic organisms.
Scientists observe that when a population of herbivorous insects is exposed to a new chemical pesticide, the insect population often begins to evolve resistance extremely rapidly.
Explain why this statement is true.
38 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.