representing variation graphically

Question 1

discontinuous variation

Answer 1

A characteristic that can only result in certain values is said to show discontinuous variation (or discrete variation). There can be no in-between values. Variation determined purely by genetic factors falls into this category. An animal’s sex is an example of discontinuous variation as there are only two possible functional values - male or female.
An example of discontinuous variation in microorganisms is the shape of bacteria. They can be spherical (cocci), rods (bacilli), spiral (spirilla) comma (vibrios) or corkscrew shaped (spirochaetes).
Discontinuous variation is normally represented using a bar chart, but a pie chart may also be used. Human blood groups also show discontinuous variation. Like most other characteristics that show discontinuous variation, it is controlled by a single gene, the ABO gene.

Question 2

continuous variation

Answer 2

A characteristic that can take any value within a range is said to show continuous variation. There is a graduation in values from one extreme to the other of a characteristic - this is known as a continuum. The height and mass of plants and animals are examples of such characteristics.
Characteristics that show continuous variation are not controlled by a single gene but a number of genes (polygenes). They are also often influenced by environmental factors.
Data on characteristics that show continuous variation are collected in a frequency table (Table 1). These data are then plotted onto a histogram (Figure 1). Normally a curve is then drawn onto the graph to show the trend.

Question 3

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