CAIE IGCSE Biology 18.1 Variation Question Bank

Practise variation questions by classifying continuous and discontinuous data, calculating values from tables and linking mutations to new alleles.

Exam points

classify continuous and discontinuous variation from graphs, tables and phenotype examples
calculate means or estimates from variation data and carry through the correct units
link mutation to genetic change, new alleles and higher rates from radiation or chemicals

Covered syllabus points

18.1.1—Variation as differences between 18.1.2—Continuous variation results 18.1.3—Discontinuous variation results 18.1.4—Discontinuous variation is usually 18.1.5—Examples of continuous 18.1.6—Mutation as genetic change 18.1.7—Mutation is the way in which new 18.1.8—Ionising radiation and some chemicals 18.1.9—Gene mutation as a random change 18.1.10—Mutation, meiosis, random mating

[Maximum number: 1]

What is a definition of variation?

having two identical alleles of a particular gene

individuals of the same species in one area

differences between individuals of the same species

the way in which new alleles are formed

[Maximum number: 5]

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

(a)

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

[ 3 ]

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

(b)

Body length is an example of continuous variation.

[ 2 ]

(i)

Suggest what causes the variation in body length in a population of fish.

[ 2 ]

[Maximum number: 3]

A scientist investigated the inheritance of fur colour in cats.

The gene for coat colour is located on the X chromosome. The gene has two alleles:
- B black
- b orange.

The X chromosome with the allele for black is represented by $\mathbf{X}^{\mathbf{B}}$ .
The X chromosome with the allele for orange is $\mathbf{X}^{\mathbf{b}}$ .
A female cat can be a mixture of these colours, described as calico.
Fig. 3.1 shows the inheritance of this condition in a family of cats.

Fig. 3.1

Coat colour in cats is an example of discontinuous variation.

Explain why coat colour is an example of discontinuous variation.

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Covered syllabus points

18.1 Variation question 1

18.1 Variation question 2

Question (a)

Question (b)

Question (i)

18.1 Variation question 3