AQA GCSE Combined Science: Trilogy Biology Paper 2 (Foundation), 2023: Question 3

9 marks · Standard Demand difficulty · Short Answer

Analyze an investigation into plant species distribution near a river, including sampling techniques, abiotic factors, and the impact of plant loss on global warming.

Practise this question

Question

A multi-part biology exam question. Figure 3 shows a map of a river between two fields with three transect lines (A, B, C) drawn perpendicular to the river bank. Figure 4 is a scatter graph with error bars showing the number of different plant species on the y-axis and distance from the river in metres on the x-axis. The graph shows a positive correlation, with the mean number of species increasing from approximately 2 at 1m to over 6 at 6m. The questions ask about placing a new transect, identifying a quadrat as the correct equipment, reading the mean value at 5m from the graph, describing the trend, identifying the purpose of range bars (uncertainty), selecting abiotic factors from a list, and explaining how a decrease in plants contributes to global warming.
Question text

03 A student investigated how the distance from a river affects the number of

different plant species.

Figure 3 shows a river between two fields.

Figure 3

03.1 A, B and C show the positions of three transects.

Where should the student position another transect for this investigation?

Draw the extra transect line on Figure 3.

[1 mark]

03.2 The student recorded the number of different plant species at 1 m intervals along

each transect.

Which piece of equipment should be used at 1 m intervals along the transect?

[1 mark]

Tick ( ) one box.

Microscope

Quadrat

Timer 12

*10* Figure 4 shows the results.

Figure 4

03.3 What was the mean number of different plant species 5 m from the river?

[1 mark]

Mean =

03.4 What is the effect of increasing distance from the river on the mean number

of different plant species?

[1 mark]

03.5 The minimum and maximum values on Figure 4 show the range of results at

each distance from the river.

*12* Why is it useful to know the range of results?

[1 mark]

Tick ( ) one box.

To calculate the mean result

To know the uncertainty of the mean

To show the mode of the results

03.6 Cows are kept in the fields.

Fewer plants are found where the cows often walk on the ground.

The number of cows is one biotic factor that affects the number of plants.

Which two factors are abiotic factors?

[2 marks]

Tick ( ) two boxes.

Consumers

Light intensity

Moisture levels

Pathogens

Predators 14

03.7 Explain why a decrease in the number of plants across the world increases

global warming.

[2 marks]

Mark scheme

Show the mark scheme The mark scheme for question 3. 03.1: line approximately perpendicular to river (1 mark). 03.2: quadrat (1 mark). 03.3: 6 (1 mark). 03.4: increases (1 mark). 03.5: to know the uncertainty of the mean (1 mark). 03.6: light intensity and moisture levels (2 marks). 03.7: more carbon dioxide in air or less carbon dioxide absorbed due to less photosynthesis (2 marks). Total marks: 9.

Question 3

AO /

Question Answers Extra information Mark

Spec. Ref.

03.1 line approximately perpendicular allow on either side of river 1 AO2

to river ignore length of line 4.7.2.1

do not accept a line parallel to RPA7

the river

AO /

Spec. Ref.

03.2 quadrat 1 AO1

4.7.2.1

RPA7

AO /

Spec. Ref.

03.3 6 / six ignore calculation / range given 1 AO2

if mean is clear 4.7.2.1

RPA7

AO /

Spec. Ref.

03.4 increases 1 AO3

4.7.2.1

RPA7

AO /

Spec. Ref.

03.5 to know the uncertainty of the 1 AO3

mean 4.7.2.1

RPA7

AO /

Spec. Ref.

03.6 light intensity 1 AO1

4.7.1.2

moisture levels 1 4.7.1.1

AO /

Spec. Ref.

03.7 more / increased carbon dioxide 1 AO2

(in air) 4.7.2.1

or 4.7.2.2

less carbon dioxide absorbed / 4.7.3.5

used (by plants)

(due to) less photosynthesis allow (due to) more decay / 1

burning (of plants)

allow 2 marks for less carbon

dioxide used for photosynthesis

if no other mark awarded allow

1 mark for carbon dioxide is

used in photosynthesis

Total Question 3 9

How to answer it

Investigating Plant Distribution & Ecology

What this question tests

This question assesses your understanding of Required Practical 7 (Ecology), specifically using transects and quadrats to measure how environmental factors affect distribution. It also covers abiotic factors and the link between photosynthesis and global warming.

Part 03.1 & 03.2

Sampling Techniques

Drawing a Transect

A transect is a line used to measure changes across an area. To show how distance from the river affects plants, your line must move away from the water.

The Drawing: Draw a straight line starting at the river bank and moving into the field, approximately perpendicular (at a 90° angle) to the river.

Correct Answers

  • 03.1: Line drawn perpendicular to the river.
  • 03.2: Quadrat

Common Pitfalls

  • 03.1: Do NOT draw the line parallel to the river. If the line stays the same distance from the water, you aren't measuring the effect of distance!
  • 03.2: Don't confuse a transect (the line) with a quadrat (the square frame used to count the plants).
Part 03.3, 03.4 & 03.5

Data Interpretation

Reading the Graph

Look at Figure 4. The "X" symbol represents the mean. To find the answer for 03.3, go to "5" on the bottom axis, move up to the "X", and read across to the vertical axis.

Understanding Range

The vertical bars show the range (the highest and lowest values). A large range means the data is spread out, which indicates higher uncertainty in the mean.

Correct Answers

  • 03.3: 6 (or six)
  • 03.4: Increases
  • 03.5: To know the uncertainty of the mean
Part 03.6

Abiotic Factors

Identifying Non-Living Factors

Key Definitions

  • Abiotic: Non-living physical or chemical parts of the environment (e.g., light, water, temp).
  • Biotic: Living factors (e.g., predators, food, pathogens).

Correct Selections

  • ✅ Light intensity
  • ✅ Moisture levels

Distractor Alert

Consumers, Pathogens, and Predators are all living organisms or biological agents, so they are biotic factors. Do not tick these!

Part 03.7

Plants & Global Warming

The Carbon Cycle Link

How to structure the 2-mark answer

You must link the biological process to the atmospheric result.

  1. Identify that plants perform photosynthesis.
  2. Explain that photosynthesis removes CO₂ from the air.
  3. Conclude that fewer plants mean more CO₂ remains in the atmosphere, trapping heat.

Mark Scheme Answer

Mark 1: More carbon dioxide in the air (or less CO₂ absorbed).

Mark 2: Due to less photosynthesis.

Note: You can also get marks for mentioning more decay or burning of plants, but photosynthesis is the most direct answer.

Common Error

Many students simply say "plants give us oxygen." While true, this does not explain global warming. You must focus on Carbon Dioxide (CO₂) to get the marks here.

Topics

Biology

Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Biology Paper 2 (Foundation), 2023. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.