Communities and competition

Farmers can increase crop yield by controlling the conditions that plants grow in.

Draw one line from each substance to how the substance increases crop yield.

Figure 1 shows a food chain for a farmer’s field.

Figure 1

Which is the secondary consumer in the food chain?

Tick () one box.

Bees are insects that live in hives.

The bees fly in and out of the hives.

Figure 2 shows a crop growing in a field.

The farmer has added bee hives to increase the number of bees in the field.

Increasing the number of bees and other insects increases crop yield.

Which are two ways that increasing the number of insects in an area will increase crop yield?

Tick () two boxes.

Some farmers increase the size of hedgerows between fields where crops grow.

Suggest one reason why.

Peat comes from peat bogs.

Peat can be used to produce garden compost.

Table 1 compares peat compost with a sample of soil.

Young plants have short roots.

Explain one advantage of growing young plants in peat compost instead of in soil.

Peat can also be burnt as fuel.

Figure 3 shows part of the carbon cycle.

Name process A and process B.

Choose answers from the box.

Peat contains carbon compounds.

Explain why burning peat contributes to climate change.

Decay is an important process in the carbon cycle.

Which two types of organism cause decay?

Tick () two boxes.

Deforestation affects the carbon cycle.

Give one use of the land after the land has been cleared by deforestation.

Buttercups are small plants.

A student investigated the distribution of buttercup plants at different distances from a tree.

Figure 4 shows a piece of equipment being used to sample two areas.

What is the scientific name of the equipment shown in Figure 4 ?

Tick () one box.

Each small square on Figure 4 represents a percentage cover of 4%.

The student counted every small square that was at least half covered by buttercup plants.

At 1 metre away from the tree, buttercup plants had a percentage cover of 20%.

Determine the percentage cover of buttercup plants at 10 metres away from the tree.

Use Figure 4.

What is the independent variable in the investigation?

Tick () one box.

What is an advantage of calculating percentage cover instead of counting the number of buttercup plants in an area?

Tick () one box.

The student investigated the percentage cover of buttercup plants around a different tree.

Table 2 shows the results.

Calculate mean value X in Table 2.

Give one conclusion about the effect of distance from the tree on the percentage cover of buttercup plants.

Use Table 2.

Give two other factors that affect the percentage cover of buttercup plants around the tree.

Do not refer to distance from the tree.

Table 2 shows the results of the investigation.

Suggest two improvements to the investigation.

Farmers can increase crop yield by controlling the conditions the plants grow in.

Maize is a crop plant.

A variety of maize has been genetically modified (GM) to be resistant to a herbicide.

Explain how growing GM herbicide-resistant maize can produce a larger yield than growing non-GM maize.

Explain how growing a GM herbicide-resistant crop can decrease the biodiversity of animals.

Bees are a type of insect.

The number of insects near a crop can be increased by planting hedgerows.

Increasing the number of bees and other insects increases crop yield.

Suggest two reasons why increasing the number of insects can increase crop yield.

Hedgerows provide habitats for insects.

Give one reason why increasing hedgerow habitats increases insect numbers.

Some farmland contains areas of peat.

When peat is dug up:

• the oxygen levels in the peat increase

• the peat decays quickly.

Explain why increasing the level of oxygen in peat contributes to climate change.

Limpets are small animals with shells.

Limpets attach to rocks on sea shores.

Figure 1 shows limpets on rocks.

Limpets eat algae.

Limpets are prey for crabs.

Give the food chain for algae, crabs and limpets.

Students estimated the population of limpets on a sea shore.

The students were given a square quadrat.

Figure 2 shows the quadrat.

Calculate the area of the quadrat in m².

The total area of the sea shore was 1800 m².

The students sampled 2% of the total area of the sea shore.

Calculate the number of times the students needed to use the quadrat for the 2% sample.

Use your answer from Question 01.2

Explain why throwing a quadrat is not a random method to estimate population size.

Do not refer to safety in your answer.

Describe one method the students could use to plan where the quadrat should be randomly placed each time.

Suggest one hazard the students should be aware of when collecting data on the sea shore.

Do not refer to throwing quadrats in your answer.

Populations of limpets are monitored to assess the impact of pollution in water.

Suggest one type of pollution in water that may affect the population of limpets.

Otters are mammals that live in river ecosystems.

Figure 5 shows an otter.

Define the term ‘ecosystem’.

Otters are an important species for the stability of the river community.

Describe two ways animal species may be important for the stability of a whole community.

Sewage was accidentally added to a river.

The sewage moved with the river water and affected:

• the number of bacteria in the water

• the concentration of dissolved oxygen in the water.

Samples of river water were analysed at different distances from where the sewage was added.

Table 2 shows the results.

The number of bacteria at 5.0 km was greater than the number of bacteria where the sewage was added.

Calculate how many times greater.

A student concluded:

‘number of bacteria concentration of dissolved oxygen’

Explain why the student’s conclusion is not correct.

Use Table 2.

Otters:

• live in water and on the land

• eat mainly fish.

The concentration of dissolved oxygen has decreased in a river where otters live.

Explain how the decrease in the concentration of dissolved oxygen in the river water will affect the population of otters.

Scientists investigated the effect of soil nitrate ion concentration on the yield of corn. This is the method used.

1. Corn plants were grown in a large box of soil.

2. The soil nitrate ion concentration in the box was kept at 0 parts per million (ppm).

3. All the corn from each plant in the box was removed and weighed.

4. The mean mass of corn per plant was calculated.

5. Steps 1 to 4 were repeated for boxes containing soil with different concentrations of nitrate ions.

Figure 2 shows the corn plants in the box with a 20 ppm soil nitrate ion concentration.

Give two variables the scientists should have controlled in this investigation.

The scientists carried out a valid investigation. Table 1 shows the scientists’ results.

Complete Figure 3. You should:

• label the y-axis

• use a suitable scale for the y-axis

• plot the data from Table 1

• draw a line of best fit.

Table 1 is repeated below.

Describe the relationship between soil nitrate ion concentration and the mean mass of corn per plant. Use data from Table 1 in your answer.

Farmers add nitrate fertiliser to fields where they grow corn. Nitrate fertilisers are expensive.

Evaluate the economic and environmental implications of adding fertiliser to soil in nitrate ion concentrations ranging from 0 to 50 ppm

This question is about biodiversity. A farmer:

• grows only wheat crops

• has used all his small fields to make a few large fields

• cuts down trees in his woodlands to burn as fuel.

What are two ways the farmer could increase biodiversity on his farm? Tick (✓) two boxes.

Students investigated the effect of cutting down trees in the woodland. This is the method used.

1. Mark out a 10 m by 10 m area where trees have been removed.

2. Place a 1 m × 1 m quadrat at six random positions in the area.

3. Record the number of plant species present.

4. Record the number of invertebrate species seen among dead leaves on the ground.

5. Repeat steps 1 to 4 in an area where there are trees.

Suggest one improvement the students could make to their method.

The students made this prediction: ‘There will be more invertebrate species living in the area where there are trees.’

Explain why the students’ prediction may be correct.

Table 1 shows the students’ results.

The students decided that one result was anomalous. Draw a ring around the anomalous result in Table 1.

How does removing trees affect the number of invertebrate species living among the dead leaves on the ground? Use Table 1.

There were more plant species growing in the area where there were no trees. Explain why.

Figure 4 shows a food chain in a garden.

bean plant → blackfly → spider → blackbird

Which term describes the spider in this food chain?

Tick (✓) one box.

Many of the spiders in the garden died.

What is likely to happen to the number of blackflies in the garden?

Tick (✓) one box.

Give a reason for your answer to Question 05.2

Table 2 shows the estimated biomass of organisms in the garden.

What conclusion can be made about biomass in food chains?

Complete Figure 5.

You should:

• label the y-axis

• plot the data from Table 2.

Explain why a garden is not a stable community.

Every year scientists have recorded the date when migrating birds arrived at summer breeding grounds in the UK.

The records show that for every 1 C increase in mean global temperature, the birds arrived one day earlier.

What will the birds be competing for when they arrive at their UK breeding grounds?

Tick two boxes.

Birds that arrive early might survive better than birds that arrive later.

Suggest one reason why.

Global temperatures are increasing every year.

This is because of an increase of greenhouse gases in the atmosphere.

Name one greenhouse gas.

Global warming affects the migration of animals.

Give one other effect of global warming.

Which two human activities cause global warming?

Tick two boxes.

Which gas in the atmosphere causes acid rain?

Tick one box.

Many biotic and abiotic factors can affect the growth of plants.

Are the factors in Table 1 biotic or abiotic? Tick one box for each factor.

Two students investigated the effect of light intensity on the distribution of small plants. The plants are growing under a tree in a park. The students made the following hypothesis: ‘As you move outwards from a tree there will be more plant growth.’

Explain why the students thought their hypothesis would be correct.

The students used two pieces of equipment. Give the scientific name of each piece of equipment.

A square frame measuring 0.5 m × 0.5 m An electronic device to measure light intensity

This is the method used.

1. Fix one end of a tape measure at the base of the tree.

2. Fix the other end of the tape measure 11 metres from the tree.

3. At 0 metres put the square frame on the ground.

4. Identify all the plant species growing inside the frame.

5. Estimate and record the percentage cover of each plant species.

6. Measure the light intensity inside the frame.

7. Put the square frame on the ground every 2 metres along the tape to 10 metres.

8. Repeat steps 4 – 6 in every frame.

Figure 1 shows the equipment in this investigation.

Calculate the total area sampled.

The whole investigation was done as quickly as possible on the same day. Suggest one reason why.

Give one way the investigation could be improved.

Table 2 shows the results.

Which plant species in Table 2 will only grow at high light intensity?

What conclusion can be made about the relationship between light intensity and the total percentage cover of plants? Use data from Table 2 in your answer.

Light intensity might not be the cause of this pattern of plant distribution. Suggest one different factor that may cause these results. Give one reason for your answer.

Reason