What you’ll learn10 learning objectivesChoose one objective for a focused lesson, or study the complete topic.18.1.1Variation as differences between• Describe variation as differences between individuals of the same speciesSyllabus objective18.1.2Continuous variation results• State that continuous variation results in a range of phenotypes between two extremes; examples include body length and body massSyllabus objective18.1.3Discontinuous variation results• State that discontinuous variation results in a limited number of phenotypes with no intermediates; examples include ABO blood groups, seed shape in peas and seed colour in peasSyllabus objective18.1.4Discontinuous variation is usually• State that discontinuous variation is usually caused by genes only and continuous variation is caused by both genes and the environmentSyllabus objective18.1.5Examples of continuous• Investigate and describe examples of continuous and discontinuous variationSyllabus objective18.1.6Mutation as genetic change• Describe mutation as genetic changeSyllabus objective18.1.7Mutation is the way in which new• State that mutation is the way in which new alleles are formedSyllabus objective18.1.8Ionising radiation and some chemicals• State that ionising radiation and some chemicals increase the rate of mutationSyllabus objective18.1.9Gene mutation as a random change• Describe gene mutation as a random change in the base sequence of DNASyllabus objective18.1.10Mutation, meiosis, random mating• State that mutation, meiosis, random mating and random fertilisation are sources of genetic variation in populationsSyllabus objective