17.1.2

Continuous & Discontinuous Variation

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Continuous vs Discontinuous Variation

A lot of the variation in the characteristics of individuals of a species is the result of both genetic and environmental influences.

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Continuous variation

  • Continuous variation is described and graphed using a scale where values are consecutive within a range.
    • Normal distribution shows most individuals close to a mean value.
  • Characteristics which show continuous variation are usually controlled by more than one gene and there may also be environmental interactions affecting phenotypes,
    • Height and mass in plants and animals show continuous variation.
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Effects of the environment

  • Continuous characteristics like height can be affected by the environment.
  • For example, someone may have genes which mean they have the potential to grow very tall.
  • However, if they grow up with poor nutrition, they may not be able to reach their full height.
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Discontinuous variation

  • Discontinuous variation is described and graphed using discrete categories with no intermediate values.
  • Characteristics showing discontinuous variation are often controlled by one polymorphic gene with little environmental effect.
    • Blood type in animals and antibiotic resistance in microorganisms show discontinuous variation.

Jump to other topics

1Cell Structure

2Biological Molecules

3Enzymes

4Cell Membranes & Transport

5The Mitotic Cell Cycle

6Nucleic Acids & Protein Synthesis

7Transport in Plants

8Transport in Mammals

9Gas Exchange

10Infectious Diseases

11Immunity

12Energy & Respiration (A2 Only)

13Photosynthesis (A2 Only)

14Homeostasis (A2 Only)

15Control & Coordination (A2 Only)

16Inherited Change (A2 Only)

17Selection & Evolution (A2 Only)

18Classification & Conservation (A2 Only)

19Genetic Technology (A2 Only)

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