Sampling and fieldwork

A student investigates the number of plant species growing in one area.

Which piece of scientific equipment will they use?

A Balance

B pH probe

C Pooter

D Quadrat

Scientists are concerned that increased pollution in a forest is affecting the population of insects living in the forest.

In an investigation, scientists estimated the population of flying insects in a forest.

• They trap the insects using nets.

• The mass of insects collected each month is then recorded. The data is collected in two different years, 1995 and 2015.

The table shows their results.

Complete the bar chart to show the mass of insects collected each year. Both years should be included on the same grid. Include a Key to identify which year the bars represent.

What two conclusions can be made about the mass of flying insects in 1995 compared to 2015?

How can the scientists’ method be developed to investigate biodiversity in the forest?

In a separate investigation, scientists estimated the population of insects that live on the forest ground.

The scientists trap insects using a pitfall trap. This is a hole in the ground that the insects fall into when they crawl along the ground.

For each estimate they use this method:

• Place pitfall traps in different areas of the forest.

• Count the total number of insects caught in the pitfall traps.

• Mark the insects.

• Release the insects where they are collected from.

A week later they trap a second sample of insects.

The scientists used an ink that is not easily washed off to mark the insects for identification.

State one other precaution that they should take when deciding how to mark the insects.

They complete their investigation during July 1995 and July 2015. This table shows the results of this investigation.

The scientists use this formula to estimate the population of insects living on the forest ground:

The population of insects in 1995 is estimated to be 855.

Use the formula to estimate the population size of insects in 2015. Give your answer to 3 significant figures.

The aim of each investigation is to see if increased pollution has affected the insect population.

The population of insects living on the forest ground increased between 1995 and 2015.

Which statements about the two investigations are true, and which are false ?

Tick (✓) one box in each row.

Scientists are concerned that increased pollution in a forest is affecting the population of insects living in the forest.

In an investigation, scientists estimated the population of flying insects in a forest.

• They trap the insects using nets.

• The mass of insects collected each month is then recorded. The data is collected in two different years, 1995 and 2015.

The table shows their results.

Complete the bar chart to show the mass of insects collected each year. Both years should be included on the same grid. Include a Key to identify which year the bars represent.

What two conclusions can be made about the mass of flying insects in 1995 compared to 2015?

How can the scientists’ method be developed to investigate biodiversity in the forest?

In a separate investigation, scientists estimated the population of insects that live on the forest ground.

The scientists trap insects using a pitfall trap. This is a hole in the ground that the insects fall into when they crawl along the ground.

For each estimate they use this method:

• Place pitfall traps in different areas of the forest.

• Count the total number of insects caught in the pitfall traps.

• Mark the insects.

• Release the insects where they are collected from.

A week later they trap a second sample of insects.

The scientists used an ink that is not easily washed off to mark the insects for identification.

State one other precaution that they should take when deciding how to mark the insects.

They complete their investigation during July 1995 and July 2015. This table shows the results of this investigation.

The scientists use this formula to estimate the population of insects living on the forest ground:

The population of insects in 1995 is estimated to be 855.

Use the formula to estimate the population size of insects in 2015. Give your answer to 3 significant figures.

The aim of each investigation is to see if increased pollution has affected the insect population.

The population of insects living on the forest ground increased between 1995 and 2015.

Which statements about the two investigations are true, and which are false ?

Tick (✓) one box in each row.

A student draws a grid containing some snails to model a habitat with snails living in it.

They then take a random sample from their grid.

This is the method they follow:

• Write numbers 1 to 15 on pieces of paper.

• Put the pieces of paper in a bag.

• Take one piece of paper out of the bag to select the number of the square.

• Record the number of snails in that square.

• Choose three more squares in the same way.

The table shows their results.

Calculate the mean number of snails in the four squares listed in the table.

The student estimates the total population by multiplying the mean by the number of squares, which is 15. The actual total population in the 15 squares is 22.

Suggest two reasons why the student’s estimate is different to the actual total population.

Suggest one way the student could change their method to improve their estimate, without counting all of the snails.

The method of capture–recapture can be used to estimate the population of snails in their actual habitat.

Describe how the student could use the method of capture–recapture to estimate the snail population. Include the name of any apparatus the student should use.

A student investigates the population of snails in a habitat.

This is the method they follow:

• Mark out a grid 2 m × 2 m: each square of the grid is 0.25 m².

• Write numbers 1 to 16 on pieces of paper and put them in a bag.

• Take one piece of paper out of the bag to select the square number.

• Record the number of snails in that square.

• Choose three more squares in the same way.

Why does the student use the pieces of paper to choose the squares in the grid?

The diagram shows the grid they use and the number of snails in the four squares they

Each square has an area of 0.25 m². The total area of the habitat is 900 m². (i)

Estimate the population of snails in the habitat.

Estimated population =........ snails

The student thinks the estimate is much larger than they would expect.

Suggest two ways the student could improve their investigation to get a more accurate estimate.

The student uses a transect to investigate the plants in the habitat.

Explain how to use a transect to investigate the distribution of different plant species in a habitat.

Two students investigate the population of daisies in a lawn. The diagram shows the lawn in front of a shed.

Complete these sentences about the method the students use to find the population of daisies.

Use the words in the list.

pooter quadrat random square

The lawn is sampled using a square frame called a........

Drop the square frame over one shoulder to provide a........ sample.

Count and record the number of daisy plants present in the square grid.

Repeat this process in 10 different areas of the lawn.

Table 16.1 shows their results.

Table 16.1

Estimate the population of daisies in the lawn.

• The students used a 0.5 m × 0.5 m frame to sample the lawn.

• The lawn size is 5 m × 3 m.

The students develop their investigation to show how the shed affects where daisies grow in the lawn.

Table 16.2 shows the results.

Table 16.2

Use the graph to determine the slope of the line.

Daisy plants require lots of light.

Explain the effect of the shed on the growth of daisies in the lawn.

Two students investigate the population of daisies in a lawn. The diagram shows the lawn in front of a shed.

Complete these sentences about the method the students use to find the population of daisies.

Use the words in the list.

pooter quadrat random square

The lawn is sampled using a square frame called a........

Drop the square frame over one shoulder to provide a........ sample.

Count and record the number of daisy plants present in the square grid.

Repeat this process in 10 different areas of the lawn.

Table 11.1 shows their results.

Table 11.1

Estimate the population of daisies in the lawn.

• The students used a 0.5 m × 0.5 m frame to sample the lawn.

• The lawn size is 5 m × 3 m.

The students develop their investigation to show how the shed affects where daisies grow in the lawn.

Table 11.2 shows the results.

Table 11.2

Plot a line graph of the results from Table 11.2. Draw a straight line of best fit.

Use the graph to determine the slope of the line.

Daisy plants require lots of light.

Explain the effect of the shed on the growth of daisies in the lawn.

White clover plants have two variants.

Cyanogenic variants produce a toxin when their cells are damaged. Acyanogenic variants do not produce a toxin.

The cells of clover plants can be damaged by freezing temperatures or by snails eating the leaves. The toxin kills snails but also damages the plant.

Table 15.1 shows growing regions of the two variants.

Complete the hypothesis to link each variant to the region it is most often found.

Acyanogenic variants are found in colder climates because........

Cyanogenic variants are found in warmer climates because........

To investigate a hypothesis a field study is needed.

Sampling techniques are used to estimate the population size of each variant in different areas.

Why are sampling techniques used instead of counting the total number of individual plants in each area?

Two students investigate the variant plants living at altitudes of 0–250 metres.

The students use random sampling as a starting point of their investigation. They then go on to complete a transect.

Explain how random sampling differs from a transect.

Explain why using a transect would develop and improve their investigation.

Fig. 15.1 shows the number of cyanogenic variant plants found in a total clover population of 200 at different altitudes.

What conclusion can be made about the effect of altitude on the distribution of cyanogenic clover?

Predict the altitude where you would expect to find mostly acyanogenic clover plants. Explain why most clover plants are acyanogenic at that altitude.

Altitude........

Explanation........

Use the theory of natural selection to explain how the cyanogenic variant of white clover plant could have developed.

White clover plants have two variants.

Cyanogenic variants produce a toxin when their cells are damaged. Acyanogenic variants do not produce a toxin.

The cells of clover plants can be damaged by freezing temperatures or by snails eating the leaves. The toxin kills snails but also damages the plant.

Table 11.1 shows growing regions of the two variants.

Complete the hypothesis to link each variant to the region it is most often found.

Acyanogenic variants are found in colder climates because........

Cyanogenic variants are found in warmer climates because........

To investigate a hypothesis a field study is needed.

Sampling techniques are used to estimate the population size of each variant in different areas.

Why are sampling techniques used instead of counting the total number of individual plants in each area?

Two students investigate the variant plants living at altitudes of 0–250 metres.

The students use random sampling as a starting point of their investigation. They then go on to complete a transect.

Explain how random sampling differs from a transect.

Explain why using a transect would develop and improve their investigation.

Fig. 11.1 shows the number of cyanogenic variant plants found in a total clover population of 200 at different altitudes.

What conclusion can be made about the effect of altitude on the distribution of cyanogenic clover?

Predict the altitude where you would expect to find mostly acyanogenic clover plants. Explain why most clover plants are acyanogenic at that altitude.

Use the theory of natural selection to explain how the cyanogenic variant of white clover plant could have developed.

A pooter is used to sample populations.

Which type of animal would be sampled using a pooter?

A Beetle

B Bird

C Fish

D Mouse

Which is the best technique to investigate the effect of shade from a tree on the types of plants growing in a field?

A Capture-recapture

B Line transect

C Pitfall traps

D Quadrat sampling in a grid

The picture shows a mealybug insect.

This mealybug is a pest for orange tree growers.

The scientists compared the number of mealybugs found on two trees, tree A and tree B.

For each tree they:

• Collected a sample of mealybugs from the tree

• Counted the number of mealybugs in each sample

• Marked the mealybugs

• Released the mealybugs back onto the tree they were collected from.

The next day another sample was collected from each tree.

Describe how the scientists should collect and mark the mealybugs.

Include the equipment they need to use.

You may include a diagram with your answer.

Write down three precautions that should be taken when deciding how to mark the mealybugs.

The table shows the results for tree A.

Estimate the population size of mealybugs on tree A.

Use the formula:

When using this method to estimate population, the scientists make several assumptions.

One assumption is that there was no immigration of mealybugs between day 1 and 2.

Suggest two other assumptions they would make.

The number of mealybugs on each tree may be affected by the light intensity.

The scientists measured the light intensity for each tree at midday on day 1 of their investigation. Light intensity is measured using a light meter.

Tree B had an estimated population of 250 mealybugs at the end of the investigation. Tree B had a higher light intensity reading than tree A.

Read this statement.

The mealybugs are thought to breed rapidly in low light conditions.

Do the results for the two trees support this statement?

Use the information above and your answer to (c)(i).

Explain your answer.

Errors can occur when taking light meter readings.

Explain how errors occur and write down one way to take more precise readings.

Which statement is not true about line transects?

A They allow study of a linear habitat like a roadside verge.

B They can be used to study which species are present in a habitat.

C They give an exact measure of how many of each species is present in a habitat.

D They show how the abundance of a species changes across a particular habitat.

The picture shows a mealybug insect.

This mealybug is a pest for orange tree growers.

The scientists compared the number of mealybugs found on two trees, tree A and tree B.

For each tree they:

• Collected a sample of mealybugs from the tree

• Counted the number of mealybugs in each sample

• Marked the mealybugs

• Released the mealybugs back onto the tree they were collected from.

The next day another sample was collected from each tree.

Describe how the scientists should collect and mark the mealybugs.

Include the equipment they need to use.

You may include a diagram with your answer.

Write down three precautions that should be taken when deciding how to mark the mealybugs.

The table shows the results for tree A.

Estimate the population size of mealybugs on tree A.

Use the formula:

When using this method to estimate population, the scientists make several assumptions.

One assumption is that there was no immigration of mealybugs between day 1 and 2.

Suggest two other assumptions they would make.

The number of mealybugs on each tree may be affected by the light intensity.

The scientists measured the light intensity for each tree at midday on day 1 of their investigation. Light intensity is measured using a light meter.

Tree B had an estimated population of 250 mealybugs at the end of the investigation. Tree B had a higher light intensity reading than tree A.

Read this statement.

The mealybugs are thought to breed rapidly in low light conditions.

Do the results for the two trees support this statement?

Use the information above and your answer to (c)(i).

Explain your answer.

Errors can occur when taking light meter readings.

Explain how errors occur and write down one way to take more precise readings.