IGCSE›Oxford AQA IGCSE Biology›Mind mapsNatural selectionOxford AQA IGCSE Biology: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsTheoriesEvolution: species change over long periodsMain explanation: natural selectionLamarck: acquired characteristics are inheritedLamarck is wrong in most casesThe sequenceIndividuals show variation from differences in genesSome are better adapted to the environmentThey are more likely to survive and reproduceAdvantageous genes passed onCharacteristic becomes more common over generationsKey ideasActs on the population, not one organismUses existing variation; does not create itNew variation comes from mutationIndividuals do not evolve in their lifetimeNatural selectionhow species changeTime scalesUsually thousands to millions of yearsHard to observe directly; fossils give evidenceBacteria change fast: short generation timeMore generations means faster changeNew species1. Isolation: populations separated by a barrier2. Variation continues in each population3. Selection favours different alleles in each4. Speciation: no fertile offspring possibleExam tipsOrganisms do not evolve because they need toCompare Lamarck with selection explicitlyIsolation alone does not make a new speciesMissing a step in the sequence loses marks