Sampling and fieldwork

Sampling is an important technique for assessing biodiversity.

Sampling is used to measure the abundance of organisms in habitats.

State why sampling is necessary when measuring the abundance of organisms in a habitat.

Explain why it is important that sampling is random.

Quadrat sampling is a useful tool for measuring the abundance and distribution of plant species.

A student sampled plants on an area of sports field. Observations recorded by the student for two of the quadrats are shown in the image below. The symbols represent different plant species.

Quadrat A
Quadrat B

State the species richness in quadrat A.

Compare the species evenness in quadrats A and B.

Some students investigate the biodiversity of flying insect species in different parts of their school grounds.

The school has an area of wildflower meadow and some planted flower beds.

This is the method they use:

1. Select an area of wildflower meadow.

2. Pass a sweep net back and forward 5 times.

3. Shake the net into a tray and close with a transparent lid.

4. Use a key to identify the types of insect.

5. Release insects.

6. Repeat the procedure 9 times in different areas of the wildflower meadow.

7. On the same day, repeat steps 1 to 6 for the planted flower beds.

Their results for the wildflower meadow are shown in the table below.

Calculate the Simpson’s Index of Diversity for the wildflower meadow.

You may use the table above for working out.

Give your answer to 2 significant figures.

Explain the significance of the value for D calculated in part (i).

Describe how the students should select their sampling areas for steps 1 and 6.

Suggest two improvements that the students could make to step 2 of their method. For each improvement explain how that would increase the validity of the results.

Suggest and explain one limitation with step 7 of the students’ method.

Identify one problem with the way in which the students categorised their flying insect species that could reduce confidence in the calculated value for Simpson’s Index of Diversity.

On a biology field trip, some students are studying an area of mixed woodland.

Three tree species dominate the woodland: oak, ash and sycamore.

There are many small herbaceous plants in the woodland, but the students choose to collect data on only one: wood sorrel.

The students choose an oak tree, an ash tree and a sycamore tree and count every individual wood sorrel plant within a 3 m radius of each tree.

The results are shown in the table.

The null hypothesis of the students’ investigation is that the species of tree would not affect the number of wood sorrel growing near it.

The students conclude that the conditions under oak trees are the most favourable of the three trees studied and that conditions under sycamore trees are the least favourable.

Calculate the |² value for the students’ data. (i)

You may use the empty columns in the table to help with your calculation.

The critical value for |² in this investigation at p = 0.05 is 5.991. (ii)

Discuss what can be concluded from the |² calculation in part. (a)(i)

The teacher suggested that, in order to have confidence in their results, the students should include data from more than one tree for each species.

The students collect all their results on the same day.

Identify two other variables the students should attempt to control when carrying out an investigation such as this.

The teacher described the mixed woodland as a climax community that had resulted from succession.

Succession involves a series of changes in community over time, known as seres.

* The first sere is the pioneer community. The final sere is the climax community.

The species that make up the pioneer and climax communities are different.

Compare the plant and animal species that make up the climax and the pioneer communities.

Extra answer space if required.

Succession involves changes in the species that live in an area over time.

State one other change that takes place in the same area over the same time.

Suggest what was present in the area that is now occupied by mixed woodland before the pioneer community arrived.

Species biodiversity is affected by many factors.

A student plans to sample the plant species in the area shown below to assess the area’s species biodiversity.

The student plans to:

• use a random number generator to generate 10 coordinates

• sample at each of the 10 coordinates

• use a point quadrat and an identification key to estimate the percentage cover of each species at each coordinate.

Describe two improvements to the student’s plan and explain why they would be improvements.

The International Union for Conservation of Nature (IUCN) compiles a list of species and their conservation status, known as the Red List of Threatened Species.

A study in 2016 assessed which factors were threats to populations of animal species.

The scientists carrying out the study selected 3789 species on the IUCN List.

They classified each population into one of five categories, based on the greatest threat to the

Outline the differences between the bird and mammal results shown in the graph.

A student looking at the graph concluded that ‘climate change is not a major threat to species biodiversity’.

Evaluate this conclusion.

Timber can be produced sustainably to maintain biodiversity in woodland.

Describe one way in which timber can be produced sustainably.

The teacher said that this method would not allow the students to measure the distribution of plant species.

Suggest an improvement to the method that would allow the distribution of plants to be measured.

Identify a limitation with step 3 of the students’ method and explain why this limitation might affect the data collected.

The students’ results are shown in the table.

Calculate the Simpson’s Index of Diversity (D) for the students’ data.

The students found grass species difficult to distinguish from one another so they decided to record any grass species as ‘grass’.

Explain how the students’ decision might have affected the calculated value for D.

On a biology field trip, the same students surveyed a large area of heather moorland.

On this occasion they did not use quadrats.

Pairs of students were each assigned a large area of moorland. They rated the abundance of plant species using the following scale:

A = Abundant C = Common F = Frequent O = Occasional R = Rare

One reason the use of quadrats was inappropriate was that many moorland plants are too large to fit in the quadrat.

Suggest one other advantage of using an ACFOR rating scale for the students’ survey.

Suggest one limitation of using an ACFOR rating scale, instead of quadrat sampling, to rate the abundance of plant species.

Ecologists were studying an area that contained three different habitats. The area is shown in the diagram below.

The ecologists sampled the area to estimate insect biodiversity.

Describe how the ecologists should choose the number and locations of their samples to ensure that the sampling is representative.

Use a calculation to support your answer.

Two of the insect species that were sampled were the large heath butterfly and the bog hoverfly.

The ecologists used the capture‑mark‑recapture technique and estimated population sizes using two different calculations: the Lincoln estimate and the Chapman estimate.

The Lincoln and Chapman formulae give different estimates for population size.

Give two further conclusions about the difference in population estimates given by the Lincoln and Chapman formulae.

The peat bog habitat had been damaged by peat extraction and by management of the neighbouring farmland. Ecologists decided to treat the peat bog in the following way:

• A buffer region was created between the peat bog and the neighbouring farmland.

• No visitors were allowed on the land.

• Ditches were blocked to raise water levels.

• Peat extraction, tree planting and the use of fertilisers were banned.

A student suggested that this was an example of preservation.

Evaluate the student’s conclusion.

Conservation agreements can be national (within a particular country) or international.

Three conservation agreements are listed in the table below.

Place ticks (✓) in the correct boxes to indicate which features are true for each of the three

Barnacles are small animals that live on rocky shores.

Adult barnacles are fixed to rocks and do not move about. They catch passing food in the water with modified limbs called cirri when the tide comes in.

Chthalamus stellatus is a species of barnacle found around UK shores.

Two students wished to estimate the population size of C. stellatus on a rocky shore near their school.

Which of the following could the students use for estimating the C. stellatus population?

1 an abundance scale, such as ACFOR 2 quadrat sampling 3 mark-release-recapture

A 1, 2 and 3

B only 1 and 2

C only 2 and 3

D only 1

Your answer

Accurate analysis of an ecosystem’s biodiversity requires a detailed classification of organisms.

The spruce pine plant is given the binomial name Pinus glabra.

Place a tick (✓) in the box next to the species most closely related to Pinus glabra.

Explain why Pinus glabra and humans, Homo sapiens, are classified in the same domain but in different kingdoms.

A scientist sampled the species of trees present in two different habitats containing Pinus glabra.

The results of the sampling are shown in Table 5.

Using Simpson’s Index of Diversity, the scientist calculated the biodiversity (D) of Habitat A as 0.71.

Use the formula given to calculate the biodiversity of Habitat B.

Show your working.

State which habitat, A or B, has the greater biodiversity.

D ( Habitat A ) = 0.71

Habitat B was situated beside a lake and showed evidence of ecological succession.

The scientist planned to investigate how the biodiversity changed from the edge of the lake to the other side of habitat B.

State the collective name of the animal and plant populations that are present at the end of primary succession.

Suggest how the scientist could achieve the following during their investigation:

Sample all stages of succession in the habitat........

Minimise sampling bias........

Sample insect biodiversity........

The scientist also measured primary production in both the woodland and lake habitats.

Suggest the units the scientist should use to measure primary production in the two habitats.

The Madidi National Park, in the South American rainforest, is home to a wide variety of species. The largest predator in the area is the jaguar. These large cats are well camouflaged and hunt mostly at night. A single individual can cover a very large area.

In 2007 the Wildlife Conservation Society (WCS) attempted to estimate the population of jaguars in the Madidi National Park.

• Digital camera traps were placed in areas that jaguars were likely to visit.

• If an infrared beam was broken by an animal, the camera was activated.

• The camera then took a photograph of the animal.

Suggest why it was not appropriate to estimate the number of jaguars using the capture-recapture technique.

Most studies estimate the population density of jaguars in the South American rainforest to be 5 individuals per 100 km².

In the 2007 study:

• 100 camera traps were set up covering an area of 271 km².

• 28 images of 9 different jaguars were recorded.

How well do these results support a population estimate of 5 individuals per 100 km²

Other evidence used to estimate the jaguar population includes footprints and reports of sightings by local humans.

Suggest one disadvantage of each of these methods for estimating the size of the jaguar population.

The Madidi National Park is also home to approximately 260 000 humans who support themselves by means of cattle-farming, and the production of timber and brazil nuts (a large nut harvested from a local native tree).

Conservationists have been working with:

• local people to promote sustainable use of these resources; and

• government agencies to maintain the quality of the national park.

Explain why the Madidi National Park is an example of conservation rather than preservation.