Sampling & fieldwork

Different species in a habitat may depend on each other for food.

Several food chains may be linked together to form a food web.

Figure 10 shows a food web in a lake.

Most organisms in the food web get their energy by eating other organisms.

Where does the pondweed get energy from?

Tick (✓) one box.

Name one organism from Figure 10 that is a primary consumer.

There are four trophic levels in Figure 10.

Which is the correct pyramid of biomass for the food web in Figure 10 ?

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One of the food chains in Figure 10 is:

10% of the biomass in each trophic level is transferred to the next trophic level.

What percentage of the biomass in the algae is transferred to the fish?

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What are two ways that energy is lost from organisms in the food chain?

Tick (✓) two boxes.

Scientists counted the number of fish, snails and worms in a sample taken from the lake.

Table 3 shows the results.

Students investigated how many daisy plants were growing in a field at different distances from a tree.

This is the method used.

1. Place a 20-metre tape measure on the ground, with the tree at 0 metres.

2. Place a 1 m² quadrat on the ground every 4 metres along the tape measure.

3. Count the number of daisy plants in each quadrat.

4. Take a soil sample from each quadrat to find the percentage of water in the soil.

Figure 14 shows the tree and the tape measure.

This is the method used for finding the percentage of water in each soil sample (step 4):

5. Weigh an empty container.

6. Place the soil sample in the container and weigh again.

7. Heat the container of soil in an oven at 100 °C for several hours.

8. Allow the container of soil to cool and weigh again.

9. Repeat steps 7 and 8 until there is no further change in mass.

Suggest why the students repeated steps 7 and 8 until there was no further change in mass.

Table 6 shows the results.

Calculate percentage X in Table 6.

Give your answer to the nearest whole number.

Describe the effect of distance from the tree on the percentage of water in the soil between 4 metres and 16 metres.

Use Table 6.

A student concluded:

‘As the water content of the soil increases, so does the number of daisy plants.’

Describe two changes to the investigation that would increase the validity of the student’s conclusion.

The percentage of water in the soil is an abiotic factor.

Suggest three other abiotic factors that might have caused more daisy plants to grow further away from the tree.

Do not refer to water in your answer.

Peat bogs are estimated to contain twice as much carbon as all the world’s forests.

Figure 13 shows a section through part of a peat bog.

Layer A contains a lot of air.

Layer B:

• contains the dead remains of plants

• has a low pH

• contains very little oxygen

• contains carbon dioxide and methane.

Explain why most of the dead remains of plants in layer B do not decay.

The peat bog in Figure 13 is a stable community.

The moss produces biomass at a rate of 340 g/m²/year.

What is the approximate biomass of the moss that becomes biomass in primary

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The sundew plant shown in Figure 13 on page 38 has leaves with sticky hairs that trap and digest insects.

Digestion of the insects releases phosphates and simple compounds of nitrogen that are used by the sundew plant.

What substance can the sundew plant make using the phosphates ?

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What substance can the sundew plant make using the nitrogen ?

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Humans have destroyed large areas of peat bog to collect peat.

The peat provides fuel and provides compost for gardeners to use.

The peat comes from layer B in Figure 13 on page 38.

Layer B:

• contains the dead remains of plants

• has a low pH

• contains very little oxygen

• contains carbon dioxide and methane.

Figure 14 shows the removal of peat from a peat bog.

Explain how the destruction of peat bogs and the use of peat affects the temperature of the Earth’s atmosphere.

Frogs are animals that lay their eggs in water. The eggs hatch as tadpoles.

Students investigated the number of tadpoles in a pond for 8 weeks.

This is the method used.

1. Collect 10 dm³ of pond water in a bucket.

2. Count the number of tadpoles collected.

3. Put the tadpoles back into the pond.

4. Repeat steps 1 to 3 another three times in different parts of the pond.

5. Repeat steps 1 to 4 at intervals for 8 weeks.

Suggest one improvement to the method.

Table 1 shows the results.

Value X is the number of tadpoles in sample 4, at 3 weeks.

Calculate value X.

Complete Figure 15 to show how the total number of tadpoles changed over the 8 weeks.

You should:

• label the x-axis

• use a suitable scale for the x-axis

• plot the data for the total numbers of tadpoles from Table 1

• draw a line of best fit.

After 0 weeks, no more tadpoles hatched in the pond.

Calculate the percentage of the tadpoles that would still be found in the pond at 4 weeks compared with 0 weeks.

Use information from Figure 15.

After 4 weeks many of the tadpoles had died.

Suggest two reasons why the tadpoles died.

Frogs are animals that lay their eggs in water. The eggs hatch as tadpoles.

Students investigated the number of tadpoles in a pond for 8 weeks.

This is the method used.

1. Collect 10 dm³ of pond water in a bucket.

2. Count the number of tadpoles collected.

3. Put the tadpoles back into the pond.

4. Repeat steps 1 to 3 another three times in different parts of the pond.

5. Repeat steps 1 to 4 at intervals for 8 weeks.

Suggest one improvement to the method.

Table 1 shows the results.

Value X is the number of tadpoles in sample 4, at 3 weeks.

Calculate value X.

Complete Figure 4 to show how the total number of tadpoles changed over the 8 weeks.

You should:

• label the x-axis

• use a suitable scale for the x-axis

• plot the data for the total numbers of tadpoles from Table 1

• draw a line of best fit.

After 0 weeks, no more tadpoles hatched in the pond.

Calculate the percentage of the tadpoles that would still be found in the pond at 4 weeks compared with 0 weeks.

Use information from Figure 4.

After 4 weeks many of the tadpoles had died.

Suggest two reasons why the tadpoles died.

Students estimated the population of buttercup plants growing on a lawn.

The lawn is a rectangle measuring 15 m 10 m.

Figure 2 shows the lawn.

This is the method used.

1. Measure the length and width of the lawn.

2. Choose five locations to sample.

3. Place a 1 m 1 m square frame at each location.

4. Record the number of buttercup plants in each square frame.

Complete the sentences.

Choose answers from the box.

The length and width of the lawn should be measured

The 1 m 1 m square frame is called a.

How should the students choose the five locations to sample?

Tick (✓) one box.

Table 1 shows the results.

The students used their results to calculate the population of buttercup plants.

Complete the sentences.

Choose answers from the box.

Multiply the length of the lawn by the width of the lawn to give the

Add up the total number of buttercup plants and divide by 5 to give

The students calculated that the population of buttercup plants on the lawn was 300.

How did the students use the results in Table 1 to calculate the population?

How could the students improve the accuracy of the estimate?

Tick (✓) one box.

One abiotic factor that affects the number of buttercup plants on the lawn is soil pH.

Give one other abiotic factor that could affect the number of buttercup plants on the lawn.

Do not refer to soil pH in your answer.

People eat fish caught in the North Sea. Figure 4 shows a food chain.

The algae make glucose by photosynthesis. Which two substances do the algae need for photosynthesis?

Tick (✓) two boxes.

What is the source of energy for photosynthesis?

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Which pyramid of biomass is correct for the food chain shown in Figure 4 ?

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Figure 5 shows the biomass of adult herring in the North Sea between

1950 and 1990.

Too many herring were caught in the 1960s. Calculate the percentage decrease in the biomass of adult herring between 1960 and 1970. Use the equation:

Give your answer to the nearest whole number.

From 1977, laws were introduced to help conserve herring.

Describe the change in biomass of adult herring from 1977 to 1990. Use data from Figure 5 in your answer.

One of the laws was to control mesh size of fishing nets. Figure 6 shows a fishing net with a legal mesh size.

Herring can live for up to 12 years. Herring start to reproduce when they are 3 to 4 years old. Explain how the control of mesh size of fishing nets has helped to conserve stocks of herring.

A student estimated the percentage cover of buttercup plants in a field. The student used a quadrat. The quadrat was divided into 25 equal squares. Figure 10 shows the quadrat.

This is the method used.

1. Place the quadrat on the ground.

2. Record how many squares in the quadrat contain buttercup plants.

3. Place the quadrat in a new position in the field.

4. Record how many squares in the quadrat contain buttercup plants.

5. Repeat steps 3 and 4 another three times.

What method should the student have used for placing the quadrat?

Tick (✓) one box.

The student calculated the percentage cover of buttercup plants for each quadrat. Table 1 shows the student’s results.

Calculate mean value X in Table 1.

Table 1 shows that quadrat 1 and quadrat 5 each had 40% cover of buttercup plants.

Figure 11 shows the results for quadrat 1 and quadrat 5.

The student’s method of estimating the percentage cover of buttercup plants is not accurate. How does Figure 11 show this?

Tick (✓) one box.

The student wanted to get a more valid estimate of the percentage cover of buttercup plants in the field. Suggest two improvements to the method to make the results more valid.

Give three environmental factors that would affect the growth of buttercup plants in a field.

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A food web contains several food chains. Figure 9 shows a food web.

The animals in Figure 9 get their energy by eating other organisms. Describe how the algae get energy.

Name one primary consumer in Figure 9.

Name one producer in Figure 9.

The different food chains in Figure 9 have different numbers of organisms. Complete Figure 10 to show a food chain in Figure 9 with five organisms, including the human.

Figure 9 shows that mackerel eat krill and squid. The biomass of mackerel is much less than the combined biomass of krill and squid. One reason for this is that the mackerel cannot digest all parts of the krill and squid. Give two other reasons.

Figure 11 shows how the biomass of adult herring in the North Sea has changed

between 1950 and 2010.

Calculate the percentage decrease in the biomass of herring between 1960 and 1977. Give your answer to the nearest whole number.

Too many herring were caught by fishermen between 1960 and 1977. Herring can live for up to 12 years and begin to reproduce when 3 to 4 years old. Laws have been introduced to help conserve herring:

• 1977 to 1981 – herring fishing was banned in the North Sea

• 1984 to present day – control of mesh size of fishing nets

• 1997 to present day – fishing quotas were introduced

• 1998 to present day – herring fishing was banned in breeding grounds during the breeding season.

Figure 12 shows how a minimum mesh size helps to conserve herring.

Figure 11 is repeated below.

Evaluate the effect of these laws on the conservation of herring stocks.

Use data from Figure 11 and information from Figure 12 in your answer.

Figure 14 shows a food chain in a pond.

Which term describes the Daphnia in this food chain?

Tick (✓) one box.

Draw a pyramid of biomass for the food chain.

Label each trophic level.

Give one reason why the total biomass of the Daphnia in the pond is different from the total biomass of the algae.

Students investigated the size of the population of Daphnia in the pond.

This is the method used.

1. Collect 1 dm³ of pond water from near the edge of the pond.

2. Pour the water through a fine net.

3. Count the number of Daphnia caught in the net.

4. Repeat steps 1–3 four more times.

Table 3 shows the results.

Calculate the mean number of Daphnia in 1 m³ of pond water.

The pond was a rectangular shape, measuring:

• length = 2.5 metres

• width = 1.5 metres

• depth = 0.5 metres.

Calculate the estimated number of Daphnia in the pond.

Use your answer from Question 07.4.

Give your answer in standard form.

Rainfall can cause fertiliser to be washed from farmland into a pond.

The students investigated the effect of fertiliser on the population of Daphnia in water from the pond.

• The students put 20 Daphnia in each of five different concentrations of fertiliser.

• The students counted the total number of Daphnia in each concentration of fertiliser after 2 weeks.

Figure 15 shows the results.

A concentration of 5.0 mg/dm³ of fertiliser caused a large increase in the population of Daphnia.

Explain why.

Figure 14 is repeated below.

The population of Hydra will decrease when 20 mg/dm³ of fertiliser is added to the pond.

Explain why.

Figure 1 shows a food chain in a pond.

Which term describes the Daphnia in this food chain?

Tick (✓) one box.

Draw a pyramid of biomass for the food chain.

Label each trophic level.

Give one reason why the total biomass of the Daphnia in the pond is different from the total biomass of the algae.

Students investigated the size of the population of Daphnia in the pond.

This is the method used.

1. Collect 1 dm³ of pond water from near the edge of the pond.

2. Pour the water through a fine net.

3. Count the number of Daphnia caught in the net.

4. Repeat steps 1–3 four more times.

Table 1 shows the results.

Calculate the mean number of Daphnia in 1 m³ of pond water.

The pond was a rectangular shape, measuring:

• length = 2.5 metres

• width = 1.5 metres

• depth = 0.5 metres.

Calculate the estimated number of Daphnia in the pond.

Use your answer from Question 01.4.

Give your answer in standard form.

Rainfall can cause fertiliser to be washed from farmland into a pond.

The students investigated the effect of fertiliser on the population of Daphnia in water from the pond.

• The students put 20 Daphnia in each of five different concentrations of fertiliser.

• The students counted the total number of Daphnia in each concentration of fertiliser after 2 weeks.

Figure 2 shows the results.

A concentration of 5.0 mg/dm³ of fertiliser caused a large increase in the population of Daphnia.

Explain why.

Figure 1 is repeated below.

The population of Hydra will decrease when 20 mg/dm³ of fertiliser is added to the pond.

Explain why.

Ragwort is a weed that grows on farmland.

Ragwort is poisonous to horses.

Plan an investigation to estimate the size of a population of ragwort growing in a rectangular field on a farm.

The herbicide glyphosate will kill ragwort and other weeds.

Scientists use bacteria for the genetic engineering of crop plants to make the crops resistant to glyphosate.

Figure 8 shows the growth of a culture of the bacteria in a solution of nutrients at 25 C

Why did the rate of reproduction increase between 2 hours and 7 hours?

After 12 hours, the rate of reproduction decreased.

Suggest three ways the scientists could maintain a high rate of reproduction in the bacterial culture.

The rate of reproduction of the bacteria is fastest at 7 hours.

How many times faster is the rate of reproduction at 7 hours than the rate at 12 hours?

Scientists transferred a gene for resistance to the herbicide glyphosate into the bacteria.

The genetically-modified (GM) bacteria can then transfer the glyphosate-resistance gene to a crop plant.

Explain the advantage of making crop plants resistant to glyphosate.

Some weed killers are selective.

Selective weed killers kill broad-leaved weed plants, but do not kill narrow-leaved grass plants.

Figure 8 shows some weeds growing on a grassy lawn.

Some students investigated the effect of a selective weed killer on the weeds growing in a lawn. They used 0.5 m 0.5 m quadrats.

The lawn was 20 metres long and 10 metres wide.

This is the method used.

1. Divide the lawn into two halves, side A and side B.

2. Place 5 quadrats in different positions on side A.

3. Place 5 more quadrats in different positions on side B.

4. Count the number of weed plants in each quadrat.

5. Spray side A with weed killer solution.

6. Spray side B with the same volume of water.

7. Repeat steps 2-4 after 2 weeks.

Suggest a method the students should have used to place each quadrat.

Give the reason for the method you suggested in Question 06.1.

Explain why the students used water on one side of the lawn instead of weed killer.

Table 3 shows the students’ results.

Calculate the mean value, X, in Table 3.

Calculate the percentage decrease in the number of weeds on side A after 2 weeks.

Use the following equation:

One student thought the results were not valid.

Suggest one improvement the students could have made to the method to make the results more valid.

Give the reason for your answer.

Some students investigated the size of a population of dandelion plants in a field.

Figure 5 shows the field.

The students:

• placed a 1 m x 1 m square quadrat at 10 random positions in the field

• counted the number of dandelion plants in each quadrat.

Table 2 shows the students’ results.

Why did the students place the quadrats at random positions?

Estimate the total number of dandelion plants in the field.

Calculate your answer using information from Figure 5 and Table 2.

Give your answer in standard form.

Quadrats 5, 7 and 8 were each placed less than 10 metres from the woodland.

These quadrats contained low numbers of dandelion plants.

The students made the hypothesis:

‘Light intensity affects the number of dandelion plants that grow in an area.’

Plan an investigation to test this hypothesis.

Light is an environmental factor that affects the growth of dandelion plants.

Give two other environmental factors that affect the growth of dandelion plants.