Sampling and fieldwork

A student investigates the effect of deforestation on the number of insects living in the soil. She uses a quadrat to sample the soil from two areas in an oak forest. One area has trees growing. The other area has been deforested. She compares the number of insects in each area. The table shows her results.

Name the independent variable in this investigation.

Suggest an explanation for these results.

The student’s results are valid and reliable. Suggest how the student made sure that her results were valid and reliable.

The student claims her results show that deforestation should be prevented. What are the advantages and disadvantages of deforestation?

The diagram shows the distribution of two plant species in a small area of a field.

A student uses a square metal frame to help count all the plants in the area.

What is the name given to the metal apparatus that the student uses?

He counts the number of plants in all of the squares he marked out in the field. Complete the table to show the number of plants of each species and the average (mean) number of plants per m².

Frequency is another measure that can be used to study distribution. Frequency is the number of squares that contain at least one plant of the species being counted. This value can also be expressed as a percentage of the total number of squares sampled. Complete the table by giving the frequency and percentage of the total number of squares sampled for bunchgrass.

Describe how the student could estimate the population size of plantain in a very large field.

The photograph shows an insect called a fire ant. These insects are a pest because their bite is painful.

Scientists compared two different methods for reducing the population of fire ants in

In the first method the scientists treated an area with pesticide. In the second method they released an organism that killed fire ants by biological control. They then estimated the number of fire ants every 6 months for a period of 30 months. The table shows the results of their investigation.

Plot a line graph to show the change in population of fire ants when pesticide was used and when biological control was used. Join the points with straight lines.

Explain the changes in the number of fire ants over the 30-month period when the area they were in was treated with pestcide.

Give two advantages of using biological control rather than pesticide to reduce the number of fire ants.

Suggest a method that could be used to estimate the population of fire ants in an area.

When trees lose leaves, they fall to the ground and form leaf litter. The leaf litter provides food for many animals. The diagram shows a food web that includes leaf litter.

Use information in the food web to complete the table. The first one has been done for you.

The following apparatus is called a Tullgren funnel. It is used to sample the number of animals living in leaf litter. The animals move away from the light and fall into the collecting pot.

A student used a Tullgren funnel to sample the number of millipedes living in leaf litter in two areas of a forest. The student took leaf litter from 5 quadrats in the centre of the forest and from 5 quadrats near the edge of the forest. The table shows the student’s results.

One stimulus that the millipedes respond to in the Tullgren funnel is light. Suggest two other stimuli that might cause millipedes to fall into the collecting pot.

State the difference in the number of millipedes found in the leaf litter samples from the two areas of the forest and suggest two reasons for this difference.

The student collects leaf litter using a quadrat. Draw a quadrat in the space below.

The table describes four different geographical regions. It also gives the amount of energy converted into plant biomass each year in each region.

Plot a bar graph on the grid to show the amount of energy converted into plant biomass each year in each region.

The amount of energy converted into plant biomass each year depends on the effect that abiotic (non-living) factors have on the rate of photosynthesis. Carbon dioxide is one of these abiotic factors. Name three other abiotic factors likely to affect the rate of photosynthesis.

Regions C and D have the same climate. Plants grown in region D have more energy converted into plant biomass than plants grown in region C. One reason for this is the use of selective breeding to produce high yielding crops.

Suggest two other reasons for more energy being converted into plant biomass in region D.

What is meant by the term selective breeding ?

Describe how you could use a quadrat to estimate the plant biomass in one of the regions.