Estimating population size and distribution using transects: practical | Combined science

Starter quiz

Which of the following organisms might you sample using a quadrat?

periwinkle ✓

bumblebee

dandelion plant ✓

fly
How many red flowers are there in the quadrat?

'7' ✓
How might you select random areas to sample using a quadrat?

Pick the area that looks the best and place the quadrat.

Using a random number generator to get coordinates to place the quadrat. ✓

Throw the quadrat and sample where it lands.

Look for where there are less plants so it is easier to sample.
When sampling an area using a quadrat, why do you need to make sure that you take as many samples as possible?

So that the sample is reliable - it represents the whole area. ✓

So that the sample is random.

So that the sample takes time to do.

So that the sample is not reliable.
A pupil records the number of chickweed plants in 5 quadrats. She records the following observations: 4, 7, 9, 5 and 10 plants. What is the mean number of chickweed plants in each quadrat?

4

5

7 ✓

10

35
Black medick plants were sampled using a quadrat (1 m²). After 10 samples, 80 black medick plants were counted. The field is 400 m². What is the estimated population of the plant?

80

320

800

3200 ✓

8000

Exit quiz

A straight line between two points that is used to take measurements and observations is called a ______.

'transect' ✓
Which of the following are abiotic factors that could be measured in a meadow while sampling an organism?

The number of plants in a quadrat.

The pH of the soil. ✓

The wind speed. ✓

How many insects are found on the species being sampled.
Match the words with their definitions.

abundance

⇔

The number of a species that is found within a habitat. ✓

biodiversity

⇔

The range of different species found within a habitat. ✓

distribution

⇔

The geographical area in which a species can be found. ✓
An example of systematic sampling is ...

when you randomly put a quadrat on the ground when sampling.

when you throw a quadrat to randomly sample an area with a quadrat.

when you place a quadrat at regular intervals along a transect to sample. ✓

when you randomly place a quadrat along a transect.
What might happen to the abundance of plant species along a transect as you leave the shade of a tall Oak tree?

The abundance of plants will not change.

The abundance of plants will increase. ✓

The abundance of plants will decrease.

There will be no plants in the shade under the tree.
Why might scientists want to place quadrats along a transect to observe and measure a species?

To work out if a species is becoming extinct.

To look at changes in the food chain diagram.

To look at changes in the abundance of a species. ✓

To measure the mean number of species in an area.

Worksheet

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Lesson Details

Key learning points

Abiotic factors such as light levels, temperature, soil moisture and pH can be measured.
Transects can be used to investigate the effects of a changing factor on the distribution and abundance of organisms.
A transect can be placed along a gradient of a factor (e.g. from shade to full sunlight).
A belt transect uses quadrats placed along the straight line to measure distribution and abundance.

Common misconception

Quadrats must always be randomly placed to survey organisms.

Quadrats can be systematically placed as part of sampling activities. This is not random sampling but regular sampling.

Keywords

Abiotic factor - Abiotic factors are the non-living components of an ecosystem.
Transect - A transect is a straight line across a habitat that is used to make measurements and observations.
Distribution - The distribution of a species is the geographical area in which a species can be found.
Abundance - Abundance is the number of organisms of a species found within a habitat.
Quadrat - A quadrat is a square frame which is used to sample populations of plants or slow-moving animals.