Practise variation by reading phenotype data, separating genetic from environmental effects and linking single-gene or polygenic inheritance to continuous or discontinuous patterns.
Variation exists in populations of a species and this may provide the opportunity for evolution to occur.
Phenotypic variation exists in many forms and has a number of possible causes.
Describe the main factors that are the cause of phenotypic variation.
The harlequin ladybird, Harmonia axyridis, is an insect that shows discontinuous variation in colour pattern and continuous variation in body size.
Within a species, the variation that is observed for a particular characteristic can be described as discontinuous or continuous.
Discontinuous variation has a different genetic basis from continuous variation.
State two differences between discontinuous variation and continuous variation, other than having a different genetic basis.
Fig. 9.1 shows three of the colour patterns seen in H. axyridis and the percentage of each in a population.
Fig. 9.1
Suggest the genetic basis of the variation in colour pattern in H. axyridis.
The body size of adult H. axyridis varies from 5 mm to 8 mm . Adult ladybirds do not grow or change size. Adults develop from larvae that hatch from eggs.
State two environmental factors that may affect adult body size in H. axyridis.