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18. Variation and selection

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  1. 18.1 Variation

    1. 18.1.1Variation as differences between

      • Describe variation as differences between individuals of the same species

    2. 18.1.2Continuous variation results

      • State that continuous variation results in a range of phenotypes between two extremes; examples include body length and body mass

    3. 18.1.3Discontinuous 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 peas

    4. 18.1.4Discontinuous variation is usually

      • State that discontinuous variation is usually caused by genes only and continuous variation is caused by both genes and the environment

    5. 18.1.5Examples of continuous

      • Investigate and describe examples of continuous and discontinuous variation

    6. 18.1.6Mutation as genetic change

      • Describe mutation as genetic change

    7. 18.1.7Mutation is the way in which new

      • State that mutation is the way in which new alleles are formed

    8. 18.1.8Ionising radiation and some chemicals

      • State that ionising radiation and some chemicals increase the rate of mutation

    9. 18.1.9Gene mutation as a random change

      • Describe gene mutation as a random change in the base sequence of DNA

    10. 18.1.10Mutation, meiosis, random mating

      • State that mutation, meiosis, random mating and random fertilisation are sources of genetic variation in populations

  2. 18.2 Adaptive features

    1. 18.2.1Adaptive feature as an inherited

      • Describe an adaptive feature as an inherited feature that helps an organism to survive and reproduce in its environment

    2. 18.2.2Interpret images or other information

      • Interpret images or other information about a species to describe its adaptive features

    3. 18.2.3Adaptive features of hydrophytes

      • Explain the adaptive features of hydrophytes and xerophytes to their environments

  3. 18.3 Selection

    1. 18.3.1Natural selection with reference

      • Describe natural selection with reference to: (a) genetic variation within populations (b) production of many offspring (c) struggle for survival, including competition for resources (d) a greater chance of reproduction by individuals that are better adapted to the environment than others (e) these individuals pass on their alleles to the next generation

    2. 18.3.2Selective breeding with reference

      • Describe selective breeding with reference to: (a) selection by humans of individuals with desirable features (b) crossing these individuals to produce the next generation (c) selection of offspring showing the desirable features

    3. 18.3.3How selective breeding by artificial

      • Outline how selective breeding by artificial selection is carried out over many generations to improve crop plants and domesticated animals and apply this to given contexts

    4. 18.3.4Adaptation as the process, resulting

      • Describe adaptation as the process, resulting from natural selection, by which populations become more suited to their environment over many generations

    5. 18.3.5Development of strains of antibiotic

      • Describe the development of strains of antibiotic resistant bacteria as an example of natural selection

    6. 18.3.6Differences between natural

      • Outline the differences between natural and artificial selection