Work through the list without notes. If you cannot do a statement, follow its link, then come back. Guide = study guide; Practice = practice questions.
Understanding
- I can explain why natural selection acts on phenotypes, and how genotypes are affected only through the phenotypes they produce. (Guide: “Selection acts on phenotypes”)
- I can tell heritable from environmental variation, and explain why only heritable variation changes the next generation. (Guide: “Heritable and non-heritable variation”; Practice Q1)
- I can define a selective pressure and give biotic and abiotic examples from a changing environment. (Guide: “Environments change and apply selective pressures”; Practice Q2, Q5)
- I can explain why sickle-cell trait raises fitness where malaria is common but not where it is absent. (Guide: “The same trait can help or harm”, Worked example 1)
- I can explain how insecticide or herbicide resistance spreads, and why the chemical does not cause the resistance. (Guide: Worked example 2; Practice Q2)
- I can explain how differences in the types or numbers of molecules in cells, such as enzyme variants, membrane lipids or extra gene copies, affect fitness in a given environment. (Guide: “Variation in molecules affects fitness”; Practice Q3, Q4, Q5)
Calculation and skills
- I can calculate relative fitness for each phenotype in each of two environments. (Guide: Worked example 1; Practice Q6)
- I can calculate the percentage of a phenotype after a round of selection. (Guide: Worked example 2)
- I can read optima and ratios from a graph of enzyme activity against temperature. (Practice Q4)
- I can calculate a seed-weighted (or offspring-weighted) mean to show how selection shifts a trait. (Practice Q7)
Reasoning
- I can state the full chain from molecule to cell function to phenotype to survival and reproduction. (Guide: “Variation in molecules affects fitness”; Practice Q5)
- I can evaluate a claim that a trait is “an advantage” by asking in which environment, using data. (Practice Q6)
- I can explain why a costly resistance trait may decline when the selective pressure is removed. (Guide: Worked example 2, Figure 2; Practice Q5)
All ticked? Move on to Topic 7.3, Artificial Selection, or return to the course roadmap.