Variation & Evolution (WJEC GCSE Science (Double Award): Biology): Exam Questions

Cystic fibrosis is a genetic condition that affects the lungs and other organs. It is caused by a mutation.

State the meaning of the term mutation.

State an environmental factor that will increase mutation rates.

Image 2.1 shows pea pods growing on pea plants (Pisum sativum).

Image 2.1

Peas grow inside the pods.

Owain wanted to see if longer pods contain more peas than shorter pods.

He:

• Picked four pods from each of the two tallest pea plants on the same day.

• Measured the length of the eight pods.

• Counted and recorded the number of peas in each of the eight pods.

The results are shown in Table 2.2.

Table 2.2

(i) Calculate the mean number of peas in the eight pods.

[2]

Mean number of peas in a pod = ….........................................………

(ii) Use the results in Table 2.2 to plot a scattergraph by:

I. labelling the vertical axis;

[1]

II. plotting the points. The first three points have been done for you (do not join the plots).

[2]

(iii) From the scattergraph:

state the relationship between pod length and number of peas.

[1]

….........................................………

(iv) Underline two statements from the list to show two ways that Owain could increase confidence in this investigation.

[2]

count the peas again

select the plants at random

measure pod length in millimetres

collect more pods from each plant

Owain used two different pea plants in his investigation. They grew in two different parts of his garden.

Choose the correct letter (A, B or C) from the list to complete the following sentence.

Variation in the number of peas in the pods is caused by:

A genetic factors only

B environmental factors only

C both genetic and environmental factors

Answer letter = ..............................

Scientific research has produced a map of all the genes present in humans.

(i) Complete the sentence below by underlining the correct term.

[1]

The complete map of human genes is called the human:

genome / gene pool / genotype

(ii) Suggest two ways by which scientists make their work known to other scientists around the world.

[2]

I.

II.

A class of year 11 students decided to carry out some genetics investigations on the fruit fly Drosophila melanogaster. Fruit flies are easily kept in school laboratories and are a good species for genetics investigations because they:

• have a short generation time (a very short time to develop from egg to adult and reproduce)

• are easy to maintain

• males (♂) and females (♀) are easy to identify

• they produce between 200 and 500 offspring per mating

The students were asked to draw a sketch of a male and a female fruit fly. A sketch is shown below.

Suggest an advantage to the students, of the fruit fly:

(i) having a short generation time;

[1]

(ii) producing large numbers of offspring.

[1]

The sentences below describe how brown rats evolved to become warfarin resistant. They are not in the correct order:

A. the mutation made the brown rat resistant to warfarin

B. the result is an increase in the population of brown rats resistant to warfarin

C. a mutation occurred in a gene

D. brown rats that were resistant to warfarin lived long enough to reproduce

E. during reproduction the useful gene is passed on to the offspring

Use letters A–E from the list above to complete the sequence below to describe how brown rats became warfarin resistant.

C → A → ..................... → ..................... → .....................

State the term used when all individuals of a species have died out.

Warfarin is an anticoagulant and has been used as a poison to control the rat population since the 1950s. Rats die from internal bleeding a few days after eating poisoned bait. In 1960, warfarin-resistant rats were found in Montgomeryshire. In the years that followed, studies found that the area where rats resistant to warfarin were detected was expanding at a rate of approximately 5 km/year.

Use your knowledge of natural selection to explain how resistance to warfarin developed and spread.

The photograph shows the banded snail, Cepaea nemoralis.

Scientists investigated variation in the mass of individual snails sampled at random from two different sites, A and B. The mass of each snail was recorded to the nearest 0.1 g. The results are shown in the bar chart.

The table below shows the mean mass of snails collected at each site.

(i) Calculate the percentage increase in the mean mass of the snails at site B compared to site A.

increase in mean mass = ……….................……… %

[2]

(ii) At which of the two sites do the snails show the greater variation in mass? Give the reason for your choice.

[1]

(iii) How did the scientists reduce bias in their investigation?

[1]

(iv) Why is it important that other scientists carry out the same investigation as these scientists?

[1]

Cepaea nemoralis shows genetic variation.

Use your knowledge of natural selection to explain the long term advantage of genetic variation to Cepaea nemoralis in a changing environment.