Continuous & Discontinuous Variation
Biology: Cambridge International A Level, topic 17.1.2
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.
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.
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.
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.
Test yourself on Continuous & Discontinuous Variation
Which of these is an example of discontinuous variation?
What characteristics show discontinuous variation?