GCSEBiologyWJECExam Questions2. Variation, Homeostasis & Micro-organisms2.4 Variation & Evolution

Variation & Evolution (WJEC GCSE Biology): Exam Questions

Exam code: 3400

51 mins5 questions
1a1 mark

The rock pocket mouse lives in a sandy desert in the United States. The mouse may be either light or dark in colour. A volcano erupted 1.7 million years ago and turned large parts of the desert into dark coloured rock. Image 5.1 shows how two locations (A and B) in the desert could have looked before the volcano erupted.

Image 5.1

Two panels showing rats on a textured background; Location A has one dark rat among light rats, Location B has one dark rat with light rats.

Image 5.2 shows how the mouse population might have changed over time after the volcano erupted.

Image 5.2

Series of six panels showing light and dark mice in two locations over time, from 1.7 to 1.5 million years ago, illustrating evolutionary changes.

Circle the cause of the changed rock colour in location B from the list below.

flooding   volcanic eruptions   human activities   forest fires

How did you do?

1b9 marks

Tables 5.3 and 5.4 show the number of light and dark coloured mice over time.

Table 5.3 – Location A

Number of mice in Location A

Time period (million years ago)

light coloured

dark coloured

Total

1.7

11

1

12

1.6

11

1

12

1.5

11

1

12

Table 5.4 – Location B

Number of mice in Location B

Time period (million years ago)

light coloured

dark coloured

Total

1.7

9

3

.....

1.6

......

6

12

1.5

2

......

12

(i) Use Image 5.2 to complete Table 5.4.

[2]

(ii) Use the information in Table 5.4 to complete Graph 5.6 for Location B by

I. adding the axes labels;

[1]

II. adding a scale to both axes;

[1]

III. drawing bars for each of the results.

[2]

Location A has been done for you on Graph 5.5.

Two bar graphs comparing light and dark mice populations over time. Location A shows more light mice; Location B's data is missing. Key included.

(iii) State what happened over time to the number of light coloured mice at

I. location A; ...........................

[1]

II. location B. ..............................

[1]

How did you do?

1c6 marks

(i) A mutation caused the dark-coloured mice to appear in a population of light coloured mice.
Define the term mutation.

[1]

(ii) Suggest and explain why the dark coloured mice had an advantage in Location B.

[2]

(iii) Suggest what will happen to the number of light coloured mice in Location B in the future.

[1]

(iv) The change in colour over time is an example of natural selection or survival of the fittest. Tick (✓) the boxes next to the two scientists who developed the theory of natural selection.

[2]

List of five scientists' names with empty checkboxes next to each: Gregor Mendel, Charles Darwin, Carl Linnaeus, Alfred Wallace, Alexander Fleming.

How did you do?

2a2 marks

Two students used modelling to illustrate the effect of camouflage in predator-prey relationships. In their investigation, spaghetti was used to model the prey and forceps to model the predator. They used the following method.

Method

  1. Mark out a 1m2 area of green grass on a field.

  2. Mix together 20 pieces of green spaghetti and 20 of red spaghetti, all 5cm in length, in a beaker.

  3. Empty the contents of the beaker in the marked area, ensure all the pieces are evenly spread out.

  4. Use a pair of forceps to pick up as many pieces of spaghetti as possible in 30 seconds. Remove these from the model.

  5. Count the number of spaghetti pieces left on the grass after 30 seconds.

  6. For each pair of a colour left on the grass, add one more piece of spaghetti of the same colour to model the process of reproduction.

  7. Repeat steps 4 to 6 twice more.

The results of the experiment are shown in Table 6

Table 6

Number of pieces of spaghetti present on the grass

Number of pieces of spaghetti added

Green

Red

Green

Red

At start

20

20

After 1st pick

18

10

9

5

After 2nd pick

22

8

11

4

After 3rd pick

27

5

(i) Suggest what would happen to the number of red spaghetti pieces present on the grass, after a 4th pick.

[1]

(ii) State the name of the evolutionary process being modelled in this investigation.

[1]

How did you do?

2b1 mark

State the type of reproduction represented in this model.

How did you do?

2c2 marks

This model has limitations. Suggest two limitations in this model.

Limitation 1..................................................................................................

Limitation 2..................................................................................................

How did you do?

3a3 marks

Haemochromatosis is a genetic condition which causes the body to absorb more iron than normal from the diet. The excess iron is stored in the body’s tissues and organs where it can cause damage. The condition mainly affects people of Northern European origin.

Haemochromatosis is caused by a mutation to the HFE gene. The HFE gene provides instructions for producing a protein which regulates iron levels in liver cells. The mutant allele is recessive to the normal allele.

(i) State the meaning of the following terms:

I. gene;

[1]

II. mutation.

[1]

(ii) State the scientific technique which could be used to identify the presence of the mutant HFE allele.

[1]

How did you do?

3b5 marks

Table 8.1 shows the amino acids coded for by each triplet code of DNA.

Table 8.1

Genetic code chart illustrating codons and corresponding amino acids, organised by first, second, and third nucleotide positions.

The DNA base sequences in Image 8.2 show part of the normal and mutant HFE alleles found at the same position on a pair of chromosomes and part of the order of amino acids for which they code.

(i) Use the information provided in Table 8.1 to insert the missing amino acids in Image 8.2.

[2]

Image 8.2

Comparison of normal and mutant alleles showing DNA and amino acid sequences. Normal: CTT TGT AGT; Mutant: CTT TAT AGT; Amino acid: leu - - - for both.

(ii) Explain how the mutant allele will give rise to haemochromatosis.

[3]

How did you do?

3c4 marks

Genetic studies suggest the original mutant HFE allele arose in a single person who lived 60 to 70 generations ago. At that time, there was much less iron in people’s diet.

Use the theory of natural selection to explain how the genetic condition haemochromatosis spread throughout the Northern European population at that time.

How did you do?

4a3 marks

Cystic fibrosis (CF) is an inherited condition caused by a DNA mutation.

Complete the sentences by selecting your answers from the words below.

radiation increase random prevent regular

A mutation is a ........................................................... change in DNA.
Ionising ........................................................... can ........................................................... the rate of mutations.

How did you do?

4b5 marks

In the family tree below, some people have CF.

Pedigree chart showing a genetic trait for cystic fibrosis. Males are squares, females are circles; shaded shapes indicate presence of CF. Key included.

(i) Calculate the percentage of people in this family tree who have CF.

[2]

Percentage = ................................................ %

(ii) State how many males and females in this family tree have CF.

[1]

Males = ................................................

Females = ............................................

(iii) In the whole population of the UK,

  • 0.01% of people have CF

  • The ratio of males to females is 1 : 1

From your answers to (i) and (ii), give two ways in which this family is different from the whole population of the UK:

[2]

I. ...............................................................................
II. ..............................................................................

How did you do?

4c2 marks

CF affects the lungs.

In a treatment, patients with CF are given DNA which does not have the CF mutation.

Complete the following sentences by underlining the correct word.

[2]

(i) The treatment is called:

chemotherapy
gene therapy
physiotherapy

(ii) The DNA is given to the patient by:

injection
infusion
inhalation

How did you do?

5a3 marks

The common limpet (Patella vulgata) is found attached to rocks on most rocky shores in Wales. Limpets attach firmly to the rocks using a muscular foot. They also rotate their shell and grind it into rock to seal it into the rock. Limpets vary in height and width.

Several common limpets with conical shells clinging to a textured, rocky surface, partially covered in green algae.

A survey was carried out to investigate the variation in the size of limpet shells on upper and lower shores in Cemlyn Bay, Anglesey in North Wales. The height and width of each shell were measured to the nearest mm as shown in Image 3.1.

Image 3.1

Shell illustration with side and top views; the side view shows height, and the top view shows width, both labelled with arrows.

These measurements were used to calculate the height : width ratio.

Ratio equals height over width colon 1

(i) State what is meant by the term variation.

[2]

(ii) State the type of variation shown in the size of the limpets.

[1]

How did you do?

5b5 marks

Table 3.2

Limpet number

Limpet shell height : width ratio

Upper shore

Lower shore

1

1.35 : 1

0.38 : 1

2

1.53 : 1

0.36 : 1

3

1.47 : 1

0.41 : 1

4

1.80 : 1

0.28 : 1

5

3.11 : 1

0.44 : 1

6

3.00 : 1

0.57 : 1

7

2.56 : 1

0.58 : 1

8

2.45 : 1

0.37 : 1

9

2.00 : 1

0.27 : 1

10

2.42 : 1

0.30 : 1

Mean

2.17 : 1

....... :1

(i) Calculate the mean shell height : width ratio for limpets sampled on the lower shore. Write your answer in Table 3.2.

[2]

(ii) State the conclusion that can be made about the height to width ratios of limpets and their position on the shore. Suggest a reason for this.

[2]

(iii) State how the students could increase confidence in their results.

[1]

How did you do?