A population of shore crabs has two inherited shell patterns: plain and mottled. Birds prey on the crabs. Scientists recorded the number of each type at the start of a study, how many survived, and how many offspring the survivors produced.
| Shell pattern | Number at start | Number that survived | Offspring produced by survivors |
|---|---|---|---|
| Plain | 50 | 10 | 12 |
| Mottled | 50 | 30 | 42 |
In a separate study, scientists followed two populations for the same 12-year period. The same inherited characteristic was favoured in both populations.
| Population | Number of generations in 12 years |
|---|---|
| A | 4 |
| B | 2 |
State which shell pattern had the greater proportion of individuals survive.
Calculate the percentage of mottled crabs that survived.
Explain how the data could lead to a greater proportion of mottled crabs in the next generation.
Suggest which population could show a change in the inherited characteristic sooner, and why.
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.