10.6 Representing Variation Graphically

Question 1

Representing Variation Graphically

Answer 1

Discontinuous - a characteristic that can only result in a certain value, there is no in-between.
Variation determined purely by genetic factors falls as discrete/discontinuous. Usually displayed in pie charts and bar charts.

Continuous - a characteristic that can take any value within a range. There is a ‘graduation from 1 extreme to the other’ (called a continuum).

E.g. height and mass of plants and animals.

Characteristics that show continuous variation are controlled by polygenes, not a single gene. Also often influenced by environmental factors; displayed in frequency tables and into histograms.

Question 2

Normal Distribution Curves

Answer 2

When continuous variation data is plotted onto a graph, they usually result in a bell-shaped curve, as a normal distribution curve.

Characteristics:
Mean, mode and median are the same
‘Bell-shape’ is symmetrical about the mean
50% of values are less than the mean & 50% is greater
Most values lie close to mean value