Ecosystems (OCR Gateway GCSE Biology)

Exam Questions

3 hours37 questions
1a
Sme Calculator
1 mark

Gardeners often turn dead plant material from their garden into compost. They then add this compost to the soil where they are growing plants.

Why do gardeners add compost to their soil?

Tick () one box.

Bs0zNNg8_q18-paper2h-nov2020-ocrgcsebio







1b
Sme Calculator
2 marks

Compost can be made in a composting bin. In the bin aerobic bacteria turn dead plant material into compost.

Some people use a different way of making compost, called bokashi. In this process the compost is made anaerobically.

The drawings show a normal composting bin and a bokashi bin.

q18b-paper2h-nov2020-ocrgcsebio
Explain the difference in the design of the two composting bins..

1c
Sme Calculator
1 mark

Scientists investigate the two methods of making compost.

This is their method:

  • Take one large pile of dead plant material
  • Divide the material into two samples of equal mass
  • Place one sample into the normal composter and place one sample into the bokashi composter
  • Measure the temperature in each composter every 10 days
  • After 40 days, measure the mass of the compost.

Write down one way that the scientists make sure that they can draw valid conclusions.

1d
Sme Calculator
9 marks

Table 18.1 shows the scientists’ temperature readings.

  Temperature of the compost (°C)
Time (days) normal compost Bokashi compost
0 26 26
10 70 27
20 53 29
30 42 31
40 28 28

Table 18.1
(i)
Plot the scientists’ results on the grid for normal and bokashi compost, and draw two curves of best fit.
pbgz4cXS_q18di-paper2h-nov2020-ocrgcsebio
[5]

(ii)
Explain why the temperature of the compost in the normal bin changed as shown in the graph.
[2]

(iii)
Explain the difference in the temperature changes between the aerobic normal compost and the anaerobic bokashi compost.
[2]
1e
Sme Calculator
5 marks

Table 18.2 shows the scientists’ results for the mass of the compost.

  Normal compost Bokashi compost
Mass at start (kg) 1500 1500
Mass after 40 days (kg) 750 1100
Table 18.2


A gas is given off in the formation of the compost. This causes most of the decrease in mass.

(i)
The percentage decrease in the mass of the normal compost is 50%.

Calculate the percentage decrease in the mass of the bokashi compost.

Give your answer to 2 significant figures.

Percentage decrease = .......................... % [3]

(ii)
The scientists concluded that the bokashi method of composting might be better for the environment.

Use your answer from part (e)(i) to justify the scientists’ conclusion.

[2]

Did this page help you?

2a
Sme Calculator
3 marks

Fig. 16.1 shows the water cycle occurring in a lake.

fig-16-1-paper2h-nov2020-ocrgcsebio

Fig. 16.1

Draw a line to the correct name for the three processes labelled A, B and C in Fig. 16.1.

q16a-paper2h-nov2020-ocrgcsebio

















2b
Sme Calculator
1 mark

Surface run-off water passes through soil and back into the lake.

Write down one reason why surface run-off water is important to organisms living in the lake.

Did this page help you?

3a
Sme Calculator
1 mark

Some students are investigating lichens.

Lichens are often studied because they are sensitive to pollution.

Lichens are made up of two different organisms: a fungi and algae.

Both the fungus and the algae gain from living together.

What biological name is given to a relationship where both organisms gain?

3b
Sme Calculator
2 marks

The students find a diagram of a lichen.q16b-paper2h-spec2018-ocrgcsebio
Using the information from the diagram suggest what the algae and fungi each gain from their relationship.

algae...........................................................
fungus.........................................................

3c
Sme Calculator
1 mark

Lichens are sensitive to pollution because they take up chemicals from the air.

The diagram shows a ‘bushy’ species of lichen and a ‘crusty’ species of lichen.q16c-paper2h-spec2018-ocrgcsebio

Bushy lichens are usually more sensitive to pollution than crusty lichens.

Use the diagrams to suggest why.

3d
Sme Calculator
8 marks

The students decide to use lichens to try and work out how polluted their school grounds are.

They read about a scale called the Lichen Diversity Value (LDV).

It is worked out in this way:

  • choose four trees in the area
  • hold a quadrat on the north side of the trunk of one tree
  • count the total number of all the lichens in the quadrat
  • then do this on the east, south and west side of the tree
  • repeat this for each tree.
(i)
Suggest how the students could choose four trees.
 [1]
(ii)
The students put their results into a table.

  Number of individual lichens found in each quadrat
Tree number North East South West
1 3 11 18 7
2 4 12 17 8
3 5 10 15 12
4 4 15 12 9
mean 4.0 12.0 15.5  

The LDV is found by adding together the four mean values.

The students calculate the mean number of lichens on the north, east and south sides of the trees.

Calculate the mean for the west side and use this to calculate the LDV.

LDV = .............................. [2]

(iii)
This scale shows the diversity of the lichens shown by the LDV.q16diii-paper2h-spec2018-ocrgcsebio
What does the LDV show about the diversity of lichens in the school grounds?
 [2]
(iv)
LDV is calculated by counting all the lichens present.

What else about the lichens could the students look for to make a better assessment of pollution?
 [3]

Did this page help you?

4a
Sme Calculator
2 marks

Some students measured the temperature inside a compost heap.

They also measured the external temperature.

On five occasions they mixed up the compost heap with garden forks.

The graph shows their results.q17-paper2h-spec2018-ocrgcsebio

(i)
The compost took 63 days to completely decompose.

Explain how the students could tell this from their graph.
 [1]
(ii)
The rate of temperature increase is greatest before the compost is mixed for the first time.

Explain how the rate of temperature change can be calculated.
 [1]
4b
Sme Calculator
2 marks

Compost decomposes more slowly above 60°C or below 30°C.

Use ideas about enzymes and decomposition to explain why this is.

4c
Sme Calculator
2 marks

Use the graph to describe how the forking helps to provide the best temperature for decomposition.

Did this page help you?

5
Sme Calculator
3 marks

The rock pocket mouse is a small grey coloured mouse that lives in Mexico.q22-paper2h-spec2018-ocrgcsebio

These mice are the main food for owls.

Rattlesnakes also feed on these mice.

The mice get most of their food from grass plants and grass seeds.

(a)

(i)
How many trophic levels are there in the feeding relationships described?
 [1]
(ii)
Draw a labelled pyramid of biomass for these feeding relationships.
[2]

Did this page help you?

6a
Sme Calculator
1 mark

The diagram shows part of a food web from a grassland.

q16-paper2h-june2018-ocrgcsebio

How many secondary consumers are shown in this food web?

6b
Sme Calculator
2 marks

A survey was set up to see if the number of badgers and hedgehogs has changed in the UK.

The number of badgers and hedgehogs were counted in different areas each year from 2003 to 2012.

The graph shows the results.
q16b-paper2h-june2018-ocrgcsebioUse the food web to suggest an explanation for the change in the number of hedgehogs shown in the graph.

Did this page help you?

7a
Sme Calculator
5 marks

The diagram shows part of a food web from a woodland.q16-paper2h-june2019-ocrgcsebio

(i)
Great tits are described as both primary consumers and secondary consumers.

Explain why.

 [2]

(ii)
Foxes are described as both predators and competitors of pine martens.

Explain why.

 [2]

(iii)
Which organism in the food web occupies the second trophic level?

 [1]

7b
Sme Calculator
7 marks

Great tits and flycatchers are both birds.

In a conservation project, scientists have built boxes for the birds to nest in. The scientists fixed the boxes on trees at different heights.

The table shows how many birds of each type used the boxes for nesting.

Height of bird box above the ground (m) Number of bird boxes used
By great tits By flycatchers
1 1 6
2 7 5
4 10 6

(i)
Draw a bar chart on the graph paper to show the scientists’ results.

The results for great tits and flycatchers should be on the same axis.q16bi-paper2h-june2019-ocrgcsebio

[4]

(ii)
The food web shows:
  • Weasels feed on great tits
  • Pine martens feed on flycatchers.
Weasels live on the ground but pine martens live in trees.

How can this be used to explain the results of the scientists’ investigation?

 [3]

Did this page help you?

8a
Sme Calculator
2 marks

The diagram shows the carbon cycle.q17a-paper2h-june2019-ocrgcsebio
Boxes 1–4 represent different processes in the carbon cycle.

Draw lines to link boxes 1–4 to the correct name for the process in the carbon cycle.q17a2-paper2h-june2019-ocrgcsebio

8b
Sme Calculator
4 marks

Scientists investigated if crops could be grown on the planet Mars.

They used a soil that was similar to the soil found on Mars. The soil contained some minerals but no living organisms.

(i)
The scientists managed to grow crops in the soil. However on Mars, the minerals in the soil would soon run out.

Explain why.
 [2]
(ii)
Living organisms could be added to the soil but there is no air on Mars. The plants would need to be grown in an enclosed structure.

At first, air would need to be added, but after a while the organisms in the soil and the plants would supply each other with the gases they need.

Explain how this would happen.
 [2]

Did this page help you?

9a
Sme Calculator
3 marks

This machine helps shred plants for a compost heap.

q20-paper2h-june2018-ocrgcsebio

The machine can shred plants into three different sizes.

This graph is in the instruction booklet for the machine.

q20-2-paper2h-june2018-ocrgcsebio

Which size of plant pieces is best for making compost?

Explain your answer.

9b
Sme Calculator
2 marks

The size of the plant pieces has an effect on the number of microorganisms in the compost.

Suggest why.

9c
Sme Calculator
3 marks

The decomposition of dead plants and animals is an important process for ecosystems.

Explain why.

Did this page help you?

10a
Sme Calculator
4 marks

The diagram shows the flow of biomass through an agricultural food chain.

q23-paper2h-june2018-ocrgcsebio

(i)
Calculate the percentage efficiency of transfer of biomass between the cattle food crop and humans.

Answer = ......................... % [2]

(ii)
Write down two ways that biomass is lost from the food chain.

1 .............................
2 .............................
[2]
10b
Sme Calculator
6 marks

High levels of light intensity can damage plants. To prevent damage, plants have a protection mechanism.

When light intensity levels get too high, the protection mechanism switches on. This stops the plant absorbing too much light.

When the light intensity drops to safe levels, the protection mechanism switches off slowly. 

Explain why this mechanism would reduce the biomass available to humans.

10c
Sme Calculator
6 marks

Higher tier only

Switching off the protection mechanism described in part (b) involves the plant making a protein.

Scientists have put extra copies of the gene for this protein into the plants. This makes the plant make more mRNA molecules.

(i)
Explain why making more mRNA will switch off the mechanism faster.

[2]

(ii)
Scientists have found that the genetically modified plants make 20% more biomass.

Use the agricultural food chain from part (a) to calculate the increase in biomass this would provide for humans.

Answer = ....................................... kg [2]

(iii)
Inserting extra copies of a plant’s gene into a plant is a type of genetic modification (GM).

Another example of GM involves inserting a bacterial gene into a plant which makes the plant produce an insecticide.

People are more likely to support genetic modification involving extra copies of the plant gene, rather than inserting the bacterial gene.

Suggest reasons why.

[2]

Did this page help you?

11a
Sme Calculator
2 marks

A gardener buys a composter to decay plant material as quickly as possible.

The composter has three sections.

q19-paper2f-june2018-ocrgcsebio
She designs an experiment to see if watering makes the plant material decay faster.

She waters:

  • Section A once a week
  • Section B once a month
  • Section C is not watered.

The gardener wants valid results. Explain one factor that the gardener should keep constant.

11b
Sme Calculator
3 marks

The gardener measures the temperature in each section for five months.

She knows that heat is given off when plant material decays.

The graph shows her results.

q19b-paper2f-june2018-ocrgcsebio
(i)
Write down two differences between the change in temperature in Section A and the change in temperature in Section C.

1. ..........................................
2. ..........................................

[2]

(ii)
The gardener decides that she should water all sections every week.

Explain why she decides this.

[1]

11c
Sme Calculator
2 marks

Each section of the composter has holes in it to let oxygen in.

Explain why this helps the material to decay.

Did this page help you?

12a
Sme Calculator
2 marks

The diagram shows the flow of biomass through an agricultural food chain.

q21-paper2f-june2018-ocrgcsebio

(i)
Calculate how much biomass is lost between the plants and humans.

Answer = .....................kg [1]

(ii)
One way biomass is lost from the food chain is by insects eating the leaves of plants.

Write down one other way that biomass is lost from the food chain.

[1]

12b
Sme Calculator
8 marks

The plants grown for cattle food often have their leaves eaten by insects.

Scientists have produced genetically modified (GM) plants that make insecticide in their leaves.

(i)
Explain why these GM plants would make more biomass available to humans.

In your answer use the diagram of the agricultural food chain and ideas about photosynthesis.

[6]

(ii)
Suggest two reasons why some people are against this type of genetic engineering.

[2]

Did this page help you?

13a
Sme Calculator
4 marks

Fig. 16.1 shows a plant that grows in South America called stevia.

fig-16-1-paper2f-nov2020-ocrgcsebio

Fig. 16.1

Fig. 16.2 shows a food web containing stevia.

MjFAi1Y2_fig-16-2-paper2f-nov2020-ocrgcsebio

Fig. 16.2

(i)
Write down the number of trophic levels in this food web.

[1]

(ii)
What is the source of energy for this food web?

[1]

(iii)
Septoria fungus is a parasite of stevia.

Explain what is meant by the term parasite.

[2]

13b
Sme Calculator
3 marks

The leaves of stevia taste very sweet. People are now trying to grow stevia as a crop.

Stevia farmers often add nematode worms to their fields.

Explain why farmers do this.

Use Fig. 16.2 in your answer.

Did this page help you?

14a
Sme Calculator
1 mark

Gardeners use dead plant material to make compost. They add this compost to soil where they are growing plants.

What do plant roots get from compost in the soil?

Put a circle enclose ring around the correct answer.

carbon dioxide    minerals    nitrogen gas    oxygen gas

14b
Sme Calculator
2 marks

Compost can be made in a composting bin. In the bin aerobic bacteria turn dead plant material into compost.

The drawing shows a composting bin.
q20b-paper2f-nov2020-ocrgcsebio
Explain why the composting bin needs holes in it.

14c
Sme Calculator
1 mark

A new way of making compost is called bokashi. In this process the compost is made anaerobically in a different type of composter.

Scientists compare the normal methods of making compost with bokashi.

This is their method:

  • Take one large pile of dead plant material
  • Divide the material into two samples of equal mass
  • Place one sample into the normal composter and place one sample into the bokashi composter
  • Measure the temperature in each composter every 10 days
  • After 40 days, measure the mass of the compost.

Why did the scientists put the same mass of compost in each composter?

Tick () one box.

q20c-paper2f-nov2020-ocrgcsebio








14d
Sme Calculator
9 marks

Table 20.1 shows the scientists’ temperature measurements.

  Temperature of the compost (°C)
Time (days) Normal compost Bokashi compost
0 26 26
10 70 27
20 53 29
30 42 31
40 28 28

                                               
Table 20.1


(i)
The scientists’ results for the normal compost are plotted on the grid.

Complete the graph by plotting the results for the bokashi compost and draw a curve of best fit.
86PhR_Gt_q20di-paper2f-nov2020-ocrgcsebio
[3]
(ii)
Describe the change in the temperature of the normal compost during the investigation.
[2]
(iii)
Use data from Table 20.1 to calculate the difference between the maximum temperature of the normal compost and the maximum temperature of the bokashi compost.

Difference = .......................... °C [2]

(iv)
Which two statements explain this difference in temperature between the two types of compost?

Tick () two boxes.
q20d-paper2f-nov2020-ocrgcsebio
[2]
14e
Sme Calculator
4 marks

Table 20.2 shows the scientists’ results for the mass of the compost.

  Normal compost Bokashi compost
  Mass at start (kg) 1500 1500
  Mass after 40 days (kg) 760 1200

Table 20.2

(i)
The mass of the normal compost has decreased by 19kg per day.

Calculate the decrease in mass of the bokashi compost per day.

Give your answer to the nearest whole number.

Decrease = .....................kg per day [3]

(ii)
Carbon dioxide is given off in the making of the compost. This causes most of the decrease in mass.

Scientists think that the bokashi method of composting might be better for the environment.

Use your answer from part (e)(i) to justify the scientists’ conclusion.

[1]

Did this page help you?