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.
There are more than 600 plant species in the genus Ipomoea. Many species are grown for their attractive flowers, and some species are used as crop plants.
The Japanese morning glory, I. nil, has over 20 different flower colour phenotypes, including shades of blue, purple, red and pink.
The flower colour of I. nil is controlled by at least four genes. The flower colour can change gradually after the flowers open each morning and can change with fluctuations in the carbon dioxide concentration of the surrounding air.
A student concluded that the flower colour phenotype in I. nil shows continuous variation.
Suggest two reasons why the student made this conclusion.
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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.
The harlequin ladybird, Harmonia axyridis, is an insect that shows discontinuous variation in colour pattern and continuous variation in body size.
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.