A group of students investigated the size of a population of daisies in the school field. 

The image below shows the field.

The table below shows the student's results.

Estimate the total number of daises in the school field.

Use the information in the image and table above.

Give your answer in standard form.

Why was the placement of the quadrats random?

Quadrats 3, 7 and 10 were randomly placed less than 10 metres from the river.

Quadrats 3, 7 and 10 contained low numbers of daisies.

The students made the hypothesis: ‘Soil moisture affects the growth of daisy plants".

Plan an investigation to test this hypothesis.

Give two other environmental factors that may alter the distribution of daisy plants.

White clover is a very common weed on lawns all over the UK.

The growth of white clover on a lawn is affected by a number factors.

Tick one box in each row to show whether the factor is biotic or abiotic.

Three students studied the distribution of white clover in a lawn by using a quadrat.

The image below shows the placement of the quadrat by each student.

Which student, A, B or C, obtained the most reliable result?

Explain your answer.

Describe the method the students should have followed to find the mean number of white clover in 1 m² of lawn using a quadrat.

The mean number of white clover plants in 1 m² of the field is 4.

The field has a total area of 500 m².

Estimate the number of white clover plants in the whole field.

A group of environmental scientists carried out a five year investigation into plant growth in an area of abandoned farmland.

They sampled the area using quadrats placed randomly.

The results are shown in the table below.

Why did the scientists place the quadrats at random positions?

Calculate the average decrease per year in the abundance of plant B over the five-year period.

Use information from the table to suggest why the abundance of plant B decreased over the five-year period.

Genetically modified (GM) plants can be made resistant to pests.

Describe an investigation that could be carried out to compare the yield of pest-resistant GM plants with that of normal plants.

The diagram below represents a belt transect showing the major types of plants growing on the bottom of a lake.

Suggest, and explain, two reasons why a much smaller population of plant D is found amongst plant C than further down in the lake.

Describe how you would use the belt transect technique to measure the abundance and distribution of plants on the bottom of a shallow lake.

Some weed killers are selective.

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

A student investigated the effect of a selective weed killer on the weeds growing in a lawn of dimensions 30 m x 20 m.

The student used a 1 m x 1 m quadrat and followed the method below.

1. Divide the lawn into two halves, side L (left) and side R (right).
2. Place 5 quadrats in different positions on side L.
3. Place 5 quadrats in different positions on side R.
4. Count the number of weed plants in each quadrat.
5. Spray side L with weed killer solution.
6. Spray side R with the same volume of water.
7. Repeat steps 2-4 after one week.

Which method should the students have used to place each quadrat?

Explain your answer.

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

The table below shows the student's results.

Calculate the mean value, X, in the table above.

Calculate the percentage decrease in the number of weeds on side L after one week.

The student's teacher told him his results were not valid.

Which improvement can the student make to ensure his results are valid?

Give the reason for your answer.

A student wanted to estimate how many ragwort plants there are in a field next to his house.

The student borrowed the following equipment from school.

• quadrat (0.5 m x 0.5 m)
• tape
• identification key

The student performed his investigation after school:

1. The student threw a quadrat over his shoulder.
2. He counted the number of ragwort plants inside the quadrat.
3. He repeated step 1 and step 2 four more times.
4. The student estimated the number of clover plants in the whole field.

Give one reason why the student needed a tape measure.

The student threw the quadrat over his shoulder.

Suggest a different way in which the student could have placed the quadrats to ensure the quadrats were placed randomly.

The student wrote down the following observations in his notebook:

• length of the field = 20 m
• width of the field = 30 m
• mean number of ragwort plants per quadrat = 8

Estimate the number of ragwort plants in the field.

What could the student do to obtain a more accurate estimate?

A student decided to investigate the distribution of a certain weed in a field of grass using a 0.5 m x 0.5 m quadrat.

The student noticed that the weed grew in patches.

She decided that it was better to count the number of squares of the quadrat covered with weed rather than to count individual weed plants.

The diagram below shows one of the quadrats used.

Estimate the number of squares of the quadrat covered with weed.

Explain how you worked out your answer.

Use your estimate to calculate the percentage of the quadrat covered with weed.

How could the student improve the investigation so that a valid estimate can be made?

Choose two of the following statements.

Scientists investigated two different species of seaweed and whether they could live only at certain positions on a rocky shore.

The scientists' results are illustrated in the diagram below.

To obtain these results, the scientist followed the method below:

1. Place a tape measure on the rocks at right angles to the sea.
2. Place a 1 m x 1 m quadrat next to the tape measure.
3. Record whether species A and species B were present or not.
4. Repeat steps 2 and 3 every metre down the shore.

Explain why the scientist placed the quadrat at regular intervals along a transect line rather than placing the quadrat randomly on the seashore.

The scientist concluded that species A is better adapted than species B to survive in dry conditions.

What is the evidence for this conclusion?

Species A is able to float in the water when the tide comes in.

Suggest how this helps it to survive.

Give one way in which the scientist can improve his investigation.

Explain how you would use a 0.5 m × 0.5 m quadrat frame and a 30 m tape measure to investigate the distribution of plants growing in and around a shallow stream.