Ten Woods of Each Type of Woodland Were Surveyed

Q6.Red squirrels live in trees. They eat seeds from the cones of conifer trees. Squirrels store cones in ‘larders’ on the ground. These larders provide food through the winter. Each red squirrel makes and defends one larder.

Scientists monitor squirrel numbers to find the best habitats for the squirrel’s survival. In one investigation, scientists estimated the numbers of squirrels in different types of woodland. Each woodland contains a different species of conifer tree.

Here is their method.

•Ten woods of each type of woodland were surveyed.

•In each wood scientists measured out two transects (strips), each 600 m long and 10 m wide.

•A scientist walked slowly down the centre of each transect, recording the number of squirrel larders he could see.

(a)Name one variable that was controlled in this investigation.(1)

(b)(i)The scientists recorded the number of larders instead of the number of squirrels they saw.How could this have increased the accuracy of the investigation? (1)

(ii)This method of counting the number of larders could have led to an inaccurate estimate of the number of squirrels.

Explain how.(2)

(c)The results of the investigation are shown on the graph.

Each bar represents the range of the number of larders in each type of woodland.

The horizontal mark on each bar represents the mean number of larders per hectare of woodland.

Is the student’s conclusion justified by the data in the graph?

Explain the reasons for your answer. (2)

Q8.This is a diagram of a belt transect showing the major types of plants growing on the bottom ofa lake.

(a)Suggest, and explain, two reasons why a much smaller population of Nitella plants is found amongst the Potamogeton plants than further down in the lake. (4)

(b) Describe how you would use the belt transect technique to measure the abundance and distribution of plants which live on the bottom of a shallow lake.(3)

Q9.Farmers grow crops of wheat.Wild plants grow, in a border 6 metres wide, between the edge of the crop and the hedge around a field.

(a) In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate.

A teacher asked a student to investigate the distribution of the different species of wild plants between the edge of the wheat crop and the hedge.

The student wrote a simple plan:

•use a 15 cm x 15 cm quadrat

•put the quadrat at A

•count the plants in the quadrat.

The student drew a diagram of the plants in the quadrat.

The student said,
‘There are 6 plants between the edge of the wheat crop and the hedge’.

The teacher said the student’s plan did not give valid results.

Why did the student’s plan for collecting data not give valid results?

Q. Suggest how the student could improve the plan to give valid results.(6)

(b) Small mammals, such as mice, sometimes shelter among the wheat plants.Mice feed on seeds.

The student improved the method.The student found that the further away from the crop, the more wild plants there were.Suggest why.(2)

Q10.Students estimated the numbers of four different types of plant growing on a school field.

The students surveyed:
•an area not walked on
•an area walked on a lot.

Each area was 1000 m2.

The bar chart shows the results.

(a) The students did not count every daisy plant in each 1000 m2 area.The students used a quadrat to estimate the number of daisies in the area that was walked on.

(i)Describe how the students should have used the quadrat to get the results shown in the bar chart.(4)

(ii)The numbers of daisies growing on the field are only estimates.

Why are these numbers only estimates?(1)

(b) Look at the bar chart.

(i)Compare the walked on area with the area not walked on.

Describe two differences in the distribution of plantain, dandelion and yarrow in the two areas.(2)

(ii)Suggest one reason for the differences you described in part (b)(i).(1)

M6. (a) area of strips / length of transects / number of transects

(b) (i) since squirrels are mobile and could be missed / counted twice

(ii) numbers of larders observed likely to be lower than actual

do not accept squirrels share larders or squirrels have
more than one larder

since unlikely that all could be spotted if 5 m away or

old larders or

squirrels moved on / died

the bars show the range of the number of squirrel larders in
the different types of woodland

although spruce woodlands have the larger ranges, some
spruce woodlands will have very low numbers of larders

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M8. (a) e.g.:
competition for light because potamogeton plants taller
competition for nutrients taller plants may have longer roots

each for 1 mark

(b) descriptions of:
measuring tape or similar quadrat
method of estimating cover (inside quadrat)

each for 1 mark

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M9.(a) Marks awarded for this answer will be determined by the Quality of Written Communication (QWC) as well as the standard of the scientific response. Examiners should apply a ‘best-fit’ approach to the marking.

0 marks: No relevant content

Level 1 (1 – 2 marks): There is a basic statement of how the plan is invalid and / or how the plan might be improved.

Level 2 (3 – 4 marks): There is a clear statement of how the plan is invalid and / or how the plan might be improved.

Level 3 (5 – 6 marks): There are detailed statements of how the plan is invalid and how the plan might be improved.

Examples of biology points made in the response:

Invalidity issues

•insufficient data eg quadrat only used once

•does not consider change between crop and hedge

•not considered different species eg only counted (total number of ) plants

•has not considered how to deal with plants overlapping edge of quadrat

•quadrat too small

Improvements:

•use of transect (eg tape measure / string)

allow random use of quadrats

•positioning of transect (from crop to hedge)

allow method of achieving randomness

•regular placement of quadrat (eg 1 metre apart)

allow record position of quadrats

•identification of species (eg text book or key)

•method of data collection (eg count each species / % cover / abundance scale)

•repeat at different points

•use a larger quadrat

•method of dealing with plants overlapping edge (eg count only if > ½)

(b) any 2 from:

•more mice closer to crop

•closer to crop more (wild plant) seeds eaten

•(so) fewer seeds grow / germinate

accept reference to competition between wild plants and wheat (1)

so fewer wild plants grow (1)

use of (selective) weed killers on crop (1)

so wild plants killed closer to crop (1)

(named) condition closer to hedge (1)

so more suitable for wild plants (1)

M10.(a) (i)any four from:

•random

•description of how randomness is achieved

e.g. ‘throw’

•idea of several times / more than once

•count plants (of each type) within quadrat(s)

•calculate mean per quadrat / m2

allow a method of doing this

•multiply by proportion of total area sampled

allow a method of doing this

•repeat in other area

e.g. do in walked on and not walked on area

(ii)may not be evenly distributed

accept haven’t counted every plant or haven’t sampled whole field

allow may miscount the plants

(b) (i)any two from

allow converse

•walked on has more plantain

•walked on has less dandelion

•walked on has less / no yarrow

allow ‘ walked on has less of the others’, if first bullet point given

if no other mark given, allow for 1 mark number of any one species or total number in both areas

ignore reference to daisy numbers

(ii)any one from:

•walking destroys (some) yarrow / dandelion

accept a reason why named plants might / might not survive, e.g. soil compacted by walking damages roots of yarrow

•plantain can’t compete with other plants or when other plants not there plantains can survive or plantain can survive being walked on

accept other factors that might affect distribution, e.g. light / water / nutrients / (specific) herbivores

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