Classification & Biodiversity (WJEC GCSE Science (Double Award): Biology): Exam Questions

Biological control agents can be effective in controlling some crop pests.

Underline the two statements in the list below which correctly relate to biological control agents.

They can reduce the need for chemical pesticides.

They cause damage to crop plants.

Pests develop resistance to biological control agents.

They are specific to certain pests.

They cannot be used on human food plants where chemical pesticides are banned.

XenTari® WG is a biological control agent which contains inactive forms of the bacterium Bacillus thuringiensis.

When water is added to the XenTari® WG the bacteria are activated. The bacteria are then sprayed onto food crops such as cucumbers, sweet peppers and tomatoes that are being attacked by certain insect pests.

(i) Explain what effect the spraying of the bacteria on a crop of tomatoes would have on the crop yield.

[2]

(ii) XenTari® WG is not yet approved for use in the UK. Explain why it is important that scientists field-test XenTari® WG before it is approved for use by the UK government.

[1]

Species A and B shown in Image 6.1 are common moorland plants.

Image 6.1

Image 6.2 shows moorland in Wales.

Image 6.2

Plant distribution can be studied using the following equipment:

• 50 m tape measure

• a 1 m² quadrat

• notebook

• pencil

• ruler

• graph paper.

Using all the above equipment, describe how you would:

• investigate the distribution of species A and B between points X and Y in Image 6.2, which are 50 m apart

• display your results.

[6 QER]

Organisms have adaptations to help them survive in their habitats. Image 2 shows a polar bear (Ursus maritimus) walking on deep snow.

Image 2

Use a ruler to draw lines to join the adaptations with their function.

The polar bear is a vertebrate.

State what is meant by the term vertebrate.

Modern classification of the giraffe identifies four different species. Their common and scientific names are shown in Table 6.5.

Table 6.5

The common names shown in Table 6.5 are anglicised (English) names. The local African peoples also have their own common names, in their own languages, for the giraffe.

(i) Explain the importance of the use of scientific names as opposed to common names.

[1]

(ii) Suggest how the modern classification of the giraffe affects the validity of Graph 6.2. Give a reason for your answer.

[1]

Explain why scientists use the scientific names Ursus americanus and Ursus maritimus when describing bears rather than the common names North American black bear and polar bear respectively.

Adult male polar bears have a mass of up to 450 kg. The male North American black bear is much smaller with a maximum mass of 158 kg. The shaded areas on the maps in Image 4.2 show the range of these two bears in North America.

Image 4.2

Use the maps in Image 4.2, and your own knowledge, to suggest a reason why the mass of an adult male polar bear is nearly three times as great as that of an adult male North American black bear.

Image 1.1 shows three insects:

Image 1.1

(i) Measure the line X – Y in centimetres.

[1]

Length of the line X – Y = ............................. cm

(ii) Multiply your answer to (i) by 2 to give the actual length of the stonefly.

[1]

Actual length = ............................. cm

(iii) Complete the list below to show the insects in order of their actual length.

[1]

Alderfly

...........................................................

...........................................................

Complete Table 1.2 by writing true or false against each statement about the three insects.

[3]

Table 1.2

State the meaning of the term biological control.

Many species of moths destroy food crops. The global effect of these pest species results in the loss of many billions of dollars per year. The stage in the life cycle of moths that causes the damage is the caterpillar, which eats the plant crop.

The simplified life cycle of most moths is shown in Image 8.1:

Image 8.1

Table 8.2 shows five species of small wasps (Trichogramma) used as biological control agents. It also shows the stage in the moth life cycle they attack and the area of farmland in different countries where these biological control agents are already used successfully.

Table 8.2

As an advisor for the United Nations you are asked to advise the Government of Peru on the use of a biological control agent to prevent moth damage in potato crops.

(i) Using all the information given, suggest the best species of Trichogramma to use and give the reason for your choice.

[2]

(ii) State one factor that would need to be investigated before Trichogramma is released into the environment in Peru.

[1]

(iii) Suggest why it is not possible to conclude, from the information in the table, that the percentage of crops damaged by moths is less in China than it is in Europe.

[1]

Longworth traps are used to capture small mammals alive. They are baited with oats and supplied with a source of water. After being examined the mammals are released unharmed. Longworth traps must be checked at least once a day. Image 5.1 shows a field vole and Image 5.2 shows a Longworth trap.

Image 5.1

Describe how you would estimate the population size of the field vole (Microtus agrestis) in a field of grass using the capture-recapture technique and Longworth traps.

You have 10 Longworth traps set at the same coordinates in the field for the whole time of the investigation and a pair of small scissors to clip 1 cm² of hair from the backs of the voles.

Population size can be estimated using the following equation:

$\text{Population size}=\frac{{\text{number in 1}}^{\text{st}}\text{ sample}\times {\text{number in 2}}^{\text{nd}}\text{ sample}}{{\text{number in 2}}^{\text{nd}}\text{ sample previously marked}}$

(NB quadrats are not required in this investigation.)

A pest control officer was asked to eradicate mice from a small food warehouse. By looking at the amount of food damage, she made an initial, on-the-spot, estimate of the number of mice in the warehouse. This initial estimate made by the pest control officer is the total number of mice shown in Image 7.1.

Image 7.1.

In order to get a better estimate of the size of the mouse population in the warehouse the pest control officer used the capture/recapture technique. She set live-capture traps in the warehouse. On the next day the traps were inspected, all the mice caught were counted, marked and released. The mice caught in this first capture are represented by (n1) in Image 7.1.

Two days later the traps were reset. The next day the traps were again inspected. The mice caught in this second capture are represented by (n₂). Within the second capture the number of marked mice were counted. These marked, recaptured, mice are represented by (n₃) in Image 7.1.

(i) Use the following equation to estimate the population size of the mice in the warehouse. Give your answer to the nearest whole number.

$\text{population size}=\frac{\text{number in 1st capture}\times \text{number in 2nd capture}}{\text{number in 2nd capture previously marked}}$

Population size = ....................................................

[2]

(ii) State how the population size estimated by the capture/recapture technique compares to the pest control officer's initial on-the-spot estimate.

[1]

(iii) State two ways in which the accuracy of the estimated population size obtained by the capture/recapture technique could be improved.

1.

2.

[2]

State three assumptions that must be made when using capture/recapture data.

1.

2.

3.

The diagram shows a plant called camelthorn (Alhagi sparsifolia).

State the genus name for camelthorn.

.........................................................................................

Camelthorn lives in dry, desert areas, where there are herbivores.

Choose two labelled features shown on the diagram and explain how each is an adaptation for camelthorn to survive in deserts.

1. ........................................................................................................................

2. .........................................................................................................................[2]

Megan investigated growth in camelthorn plants in two different conditions.

Plant A was given 250 cm³ of water each day. Plant B was watered once only at the start of the investigation. The diagram shows the appearance of the two plants at seven days.

Compare the root growth in the two plants and suggest how root growth in plant B is an adaptation to dry soil.

The brown rat (Rattus norvegicus) spreads disease. Warfarin is a poison used to kill brown rats. Over time, many brown rats have evolved to become resistant to warfarin.

State the genus of the brown rat.

The brown rat is a vertebrate. State what is meant by the term vertebrate.

The photograph shows Erinaceus europaeus.

Erinaceus europaeus has many common names, such as hedgehog, urchin and furze-pig.

State:

(i) the Kingdom to which the hedgehog belongs;

[1]

(ii) the Genus name for the hedgehog.

[1]

Explain why scientists use the scientific name, rather than common names for organisms.

Cardiff Bay is a 2.0 km² freshwater lake. The Bay is not tidal but visiting yachts, from all over Europe, can enter the Bay from the sea, through locks. The Bay is fed by two rivers, the Taff and the Ely.

The following public information notice has been posted in Cardiff Bay.

(i) Invasive species are also known as alien species. Explain what is meant by the term invasive species and why they are a problem.

[2]

(ii) In the public information notice opposite there is an error in the way in which the scientific name of the killer shrimp has been written. Identify the error by writing the scientific name in the correct form.

[1]

(iii) Killer shrimps feed on native freshwater shrimps, aquatic insects and small fish. State how the biodiversity of the UK will be affected by the killer shrimp.

[1]

The kestrel (Falco tinnunculus) is a bird of prey found in Pembrokeshire, Wales. The photographs show a kestrel in flight and nesting.

Surveys are carried out by the Welsh Kite Trust to monitor the numbers of kestrels in Pembrokeshire. The data gathered by some of these surveys are shown in Table 6.1.

Table 6.1

(i) Calculate the percentage decrease in breeding pairs between 2011 and 2016.

Use the formula below.

$\text{Percentage decrease}=\frac{\text{number of breeding pairs in 2011}-\text{number of breeding pairs in 2016}}{\text{number of breeding pairs in 2011}}\times 100$

Percentage decrease in breeding pairs = ....................................................

[2]

(ii) Suggest two possible reasons for this decrease.

1. ..................................................................................

2. ....................................................................................

[2]

Image 6.2 shows a map of the nesting sites of kestrels in Pembrokeshire.

Image 6.2

State one conclusion that can be made about where kestrels generally choose to nest. Suggest a reason for this.

Students used a quadrat to investigate the abundance of dandelions (Taraxacum officinale) on the school rugby pitch.

The method they used was:

1. Use a 1 m² quadrat.

2. Use a random number generator to place the quadrat on the rugby pitch.

3. Count the number of dandelions in the quadrat.

4. Repeat steps 2 and 3 another 5 times.

5. Calculate a mean.

6. Calculate the number of dandelions on the school rugby pitch.

The results they obtained are given in Table 10.1.

Table 10.1

(i) Draw a circle around the anomalous result in Table 10.1.

[1]

(ii) Calculate the mean number of dandelions per quadrat and write your answer in Table 10.1. Do not use the anomalous result in your calculation.

[2]

The teacher said that he did not have confidence in the mean. Suggest why.

The total area of the school rugby pitch is 7 350 m². Use your answer to part (a)(ii) to calculate the total number of dandelions on the school rugby pitch.

Total number of dandelions on the school rugby pitch = ...........................

State the name of the method the students should use to investigate the distribution of the dandelions across the pitch.

Cod are important in maintaining biodiversity in the North Sea.

Choose the letter (A – C) from the list which defines biodiversity for an area.

Read the following information about cod.

• Overfishing in the second half of the 20th century had a serious effect on the stocks of adult cod in the North Sea.

• The total stock of adult cod is estimated annually.

• The safe stock is the minimum mass of the adult cod population that should be left in the sea each year to ensure that the cod remains at sustainable levels.

• In 1996, scientists predicted that without action there would be no adult cod in the North Sea by 2015.

• In 2005, the European Commission put an annual limit (quota) on the mass of cod that could be taken by each vessel fishing in the area.

The graph shows the total annual catch of cod and the stock of adult fish remaining in the North Sea from 1965 to 2015.

(i) The safe stock is 150 000 tonnes.

Use a ruler to draw a straight line on the grid to show the safe stock, from 1965 to 2015.

[1]

(ii) Use the data in the graph to answer the following questions.

I. Calculate the difference in mass between the total catch in 1982 and the safe stock.

Difference in mass = .................................... thousand tonnes

[2]

II. One tonne contains 120 adult cod.

Calculate the number of adult cod in the safe stock.

Number of adult cod in the safe stock = ................................

[2]

(iii) Describe the evidence that:

I. shows overfishing beyond a sustainable level took place between 1971 and 2005;

[2]

II. supports the prediction made by scientists in 1996, that 'without action there would be no adult cod in the North Sea by 2015';

[1]

III. shows the fishing quota of 2005 had an effect on the cod population.

[1]

Maintaining biodiversity ensures a continued food supply for humans.

Give one other benefit to humans of maintaining biodiversity.

Rhys wanted to investigate the abundance and distribution of four plant species as he moved from the edge of a woodland towards the centre. He laid down a tape measure to form a transect. Using a 0.25 m² quadrat he sampled every five metres along the transect line, estimating the percentage area cover of each species. The diagram shows the area of woodland that was investigated.

His results are shown in the table.

Draw a line graph of the results for both Dog's Mercury and Bluebell on the grid below. Label each line.

(i) State the term used to refer to competition between two different species.

....................................................................................

[1]

(ii) Describe the results for Dog's Mercury and Bluebell. Suggest an explanation for your answer.

[2]

(i) Jim suggested to Rhys that he should have carried out random sampling. State why it would be unsuitable to use a random sampling method in this investigation.

[1]

(ii) Suggest one improvement Rhys could make to his method.

[1]

Biodiversity is a measure of the variety of different species and the number of individuals within those species in an area. State two reasons why it is important that biodiversity is maintained.

Ceri used a data logger to measure light intensity at six sites (A – F) along a 120 m transect through a wood, as shown below.

The results below are shown on her computer screen.

(i) Describe how light intensity changes along the transect.

[2]

(ii) Ceri thought that light intensity affected the number of plant species growing under the trees along the transect.

She counted the number of plant species present at each site. The results are shown in the table.

Complete a bar chart on the grid below by:

I. labelling the vertical axis;

II. using a ruler to draw bars for the number of plant species at each site.

[3]

(iii) State Ceri's hypothesis.

[1]

(iv) Do the results of the investigation support her hypothesis? Give a reason for your answer.

[1]

(v) Apart from light intensity, suggest one other environmental factor that might affect the number of plant species growing under the trees.

The table shows the number of two species of bacteria (A and B) in samples of seawater taken near a beach.

(i) The graph below shows how the total number of species A and B changed between March 15th and September 15^th.

I. Between which two sampling dates was the increase in the total number of species A and B the fastest?

Between ……….................……… and ……….................………

[1]

II. If the total number of species A and B in the sample is likely to be greater than 700 000 per cm³ in any month, people are advised to stay out of the sea.

A safety officer said:

"On June 15^th, I decided to advise people to stay out of the sea until further notice."

Explain why the safety officer made this decision, even though the seawater was safe on that date.

[2]

(ii)

I. Describe the trends shown in the table for the numbers of species A and B.

Species A:

Species B:

[2]

II. Use your answer to part (I.) to explain why the sampling should continue into October.

[1]

A group of students were asked to calculate the population size of garden snails (Helix aspersa) in 5 different areas of similar size in the school grounds. They sampled the five areas of the school grounds early in the morning on a damp day. The students sampled each area once only and counted the number of snails they found. The shell of each snail was marked with a small spot of white ink. The snails were then released.

Approximately one week later, on a damp morning, the students sampled the same areas of the school grounds a second time. This time they recorded the number of recaptured snails (the ones that had been marked with white ink a week earlier) and the number of snails which had not been marked with white ink.

The table below shows the capture – recapture results obtained by the students.

Use the equation below to calculate the population size for the snails living in the vegetable garden. Write your answer in the table above.

Space for working.

State one way in which the students kept their investigation fair.

The song thrush (Turdus philomelos) feeds on snails. During the week after marking the snails with white ink some of the students noticed that the number of song thrushes in the five areas of the school grounds had increased. This increase may have been due to a problem resulting from the students' method. Suggest why the number of song thrushes increased and how the students could overcome the problem.