Question 1 Medium
A 1 m² quadrat has 25% of its squares covered by moss. What is the percentage cover of moss?
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Answer: 25%
- Percentage cover is the percentage covered.
- It is 25%.
Fieldwork: quadrats, transects and population estimates: GCSE Combined Science Biology practice questions
A second set of questions on fieldwork: quadrats, transects and population estimates. They are different from the ones on the topic page. Try each, then open the answer and compare your working.
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Question 2 Medium
Name a type of transect that uses quadrats placed at set intervals along a line.
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Answer: belt transect
- A belt transect samples a strip of known width.
- It uses quadrats along the line.
Question 3 Hard
The mean number of dandelions in 0.5 m² quadrats is 3. How many dandelions are there per m²?
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Answer: 6
- Divide by the quadrat area.
- 3 ÷ 0.5 = 6.
Question 4 Hard
There are 6 dandelions per m². The field is 600 m². Estimate how many dandelions are in the field.
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Answer: 3600
- Multiply the number per m² by the area.
- 6 × 600 = 3600.
Question 5 Hard
In a transect, the number of plants falls as soil moisture falls. Does this prove that moisture is the cause?
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Answer: no
- A correlation shows a link.
- Other factors could be the cause, so it does not prove it.
Question 6 Hard
A student uses 2 quadrats, another uses 20. Whose mean is likely to be more reliable?
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Answer: the student who used 20
- A larger sample reduces the effect of chance.
- The student with 20 quadrats has the more reliable mean.
Question 7 Hard
Counts in four quadrats are 3, 7, 5 and 5. Calculate the mean.
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Answer: 5
- Total = 3 + 7 + 5 + 5 = 20.
- 20 ÷ 4 = 5.
Question 8 Hard
Why is it a problem if a student chooses where to put the quadrats themselves?
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Answer: bias
- They may choose places with more plants.
- This makes the sample biased.
Quick checks
Short questions with options. Choose one before you open the answer.
Check 1
Why do ecologists take samples?
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It is not practical to count every organism, so a sample is used to estimate the whole.
Check 2
What is a quadrat?
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A square frame of known area used for sampling.
Check 3
Why should quadrats be placed at random?
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To avoid bias and give a representative sample.
Check 4
How can you place quadrats at random?
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Use random numbers as coordinates on a grid made with two tape measures.
Check 5
Why use a large sample?
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It reduces the effect of chance and gives a more reliable mean.
Check 6
How do you find the mean number per quadrat?
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Add up the counts and divide by the number of quadrats.
Check 7
How do you find the number per m² from a 0.25 m² quadrat?
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Divide the mean per quadrat by 0.25.
Check 8
How do you estimate the population of an area?
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Number per m² multiplied by the total area in m².
Check 9
When do you use percentage cover?
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When plants are too close together to count individually.
Check 10
What is a transect?
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A line or belt across a habitat along which organisms are recorded.
Check 11
What is a line transect?
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You record the organisms that touch a tape measure at set intervals.
Check 12
What is a belt transect?
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Quadrats are placed at set intervals along a line, so a belt of known width is sampled.
Check 13
When is a transect used?
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To see how the distribution of organisms changes across a habitat.
Check 14
Name three ways to measure abiotic factors in a habitat.
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Light meter, soil moisture meter and thermometer or pH probe.
Check 15
Why does a correlation not prove cause?
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Another factor could be responsible for the pattern.
Check 16
What is an abiotic factor?
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A non-living factor such as light, temperature or soil pH.
Check 17
What is a representative sample?
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A sample that gives a fair picture of the whole area.
Check 18
Why use the same quadrat size every time?
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To make the counts comparable.
Check 19
What safety care is needed in fieldwork?
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Check for hazards, wear suitable clothing and wash your hands afterwards.
Check 20
What does the mean of 4, 6, 8, 5 and 7 equal?
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6.
Check 21
What is a population?
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All the organisms of one species in an area.
Check 22
What is a community?
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All the populations of different species living in an area.
Check 23
What is a habitat?
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The place where an organism lives.
Check 24
What does the investigation tell you if numbers fall as light falls?
Show answer
There is a link, but it does not prove light is the cause.
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