QuestionQuestionConceptConceptDocumentDocument

18. Variation and selection

Start with Concept to understand a topic, then use Question Bank to check what you know.

3 topics · 19 learning objectives

Your progress

Sign in to see your mastery and mistakes.

  1. 18.1 Variation

    1. • Describe variation as differences between individuals of the same species

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

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

    5. • Investigate and describe examples of continuous and discontinuous variation

    6. • Describe mutation as genetic change

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

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

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

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

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

    6. • Outline the differences between natural and artificial selection