18. Variation and selection
- Syllabus
- 0610–2026–2027
- Section
- 18
- Level
- —
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In this section
Topic 18.1
18.1 Variation
Objectives in this topic
18.1.1—Variation as differences between
- Describe variation as differences between individuals of the same species
18.1.2—Continuous variation results
- State that continuous variation results in a range of phenotypes between two extremes; examples include body length and body mass
18.1.3—Discontinuous 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
18.1.4—Discontinuous variation is usually
- State that discontinuous variation is usually caused by genes only and continuous variation is caused by both genes and the environment
18.1.5—Examples of continuous
- Investigate and describe examples of continuous and discontinuous variation
18.1.6—Mutation as genetic change
- Describe mutation as genetic change
18.1.7—Mutation is the way in which new
- State that mutation is the way in which new alleles are formed
18.1.8—Ionising radiation and some chemicals
- State that ionising radiation and some chemicals increase the rate of mutation
18.1.9—Gene mutation as a random change
- Describe gene mutation as a random change in the base sequence of DNA
18.1.10—Mutation, meiosis, random mating
- State that mutation, meiosis, random mating and random fertilisation are sources of genetic variation in populations
Topic 18.2
18.2 Adaptive features
Objectives in this topic
18.2.1—Adaptive feature as an inherited
- Describe an adaptive feature as an inherited feature that helps an organism to survive and reproduce in its environment
18.2.2—Interpret images or other information
- Interpret images or other information about a species to describe its adaptive features
18.2.3—Adaptive features of hydrophytes
- Explain the adaptive features of hydrophytes and xerophytes to their environments
Topic 18.3
18.3 Selection
Objectives in this topic
18.3.1—Natural 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
18.3.2—Selective 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
18.3.3—How 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
18.3.4—Adaptation 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
18.3.5—Development of strains of antibiotic
- Describe the development of strains of antibiotic resistant bacteria as an example of natural selection
18.3.6—Differences between natural
- Outline the differences between natural and artificial selection