CAIE IGCSE Biology 18.1.2 Continuous Variation

Practise recognising continuous variation as a range of phenotypes between two extremes and describing its distribution.

Exam points

state that continuous variation produces a range of phenotypes between two extremes
identify body length and body mass as continuous variables
describe a frequency graph using range, mode, spread and comparative data values

[Maximum number: 3]

Carp are a type of fish. Researchers in Brazil measured the body lengths of a population of carp in a river in 1998 and again in 2008.

Histograms of their results are shown in Fig. 2.1.

Fig. 2.1

Describe the variation in body length of the carp population in 1998. Use the data in Fig. 2.1 to support your answer.

1 mode is / majority / most fish are, between 12.1 and
16.0 cm long;
2 range / body length, varies up to $24 \mathrm{~cm} /$ varies 0 to
24 cm ;
3 very few fish are less than 4 cm ;
4 no fish longer than 24 cm ;
5 normal distribution / bell-shaped curve / similar number of fish longer and shorter than the mean;
AW
6 Data quote of range with units and thousands of fish;
7 AVP ref to actual range may be shorter than 0-

A mean

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18.1.2—Continuous variation results question 1