Estimating population size using quadrats: practical | Combined science

Starter quiz

True or false? A bottle garden is an example of an ecosystem.

True ✓

False
What is this piece of equipment called?

'quadrat' ✓
Which of the following populations of organisms might you use a quadrat to sample?

dandelion plants ✓

wasps

starfish ✓

blackbirds
The diagram shows a pitfall trap. Which of the following organisms might be sampled using this piece of equipment?

beetles ✓

bees

pigs

daisy plants
Rainfall in a habitat is an example of ...

both a biotic and an abiotic factor.

a biotic factor.

an abiotic factor. ✓
When carrying out a mark-release-recapture experiment we put a small mark on the organism so that we know it has been captured before. What is important to remember when marking an organism?

To make sure that the mark stands out so it is easy to count.

To use a substance that is harmless to the organism. ✓

To make sure that the mark is large.

To make the organism stand out to a predator.

Exit quiz

Abundance means ...

how organisms interact with each other in the environment.

how many different organisms there are in a habitat.

the number of one species that is found in a habitat. ✓

how often a quadrat is used in an investigation.
Which of the following is true about quadrats?

Quadrats should be placed randomly by throwing them.

More reliable results are given by taking a large sample. ✓

Quadrats should only be used in the summer when plants are flowering.

Quadrats are useful to sample populations of mice.
What is the area of a quadrat that measures 0.5 m × 0.5 m?

1 m²

0.5 m²

0.25 m² ✓

0.1 m²
Look at the results from a quadrat survey of dandelion plants. Calculate the mean number of dandelion plants in each quadrat.

78

20

10

7.8 ✓

0.78
Ten 1 m² quadrats were placed in a 40 m² field. A mean of 2 snails were found in every quadrat. Estimate the population size of the whole field.

8

40

80 ✓

800
The results from a quadrat survey of dandelion plants in a school field is shown. Each quadrat is 1 m². If the school field is 1000 m², estimate the total population size of dandelion plants.

'78 000' ✓

Worksheet

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Lesson Details

Key learning points

Quadrats can be used to sample an area to estimate population size (abundance).
Quadrats are used to sample plants and slow-moving, small animals.
Quadrats can be placed at random to help avoid bias.
Using quadrats to estimate population size (species abundance) in an area.
Using quadrats to investigate the population size of a plant species using random sampling.

Common misconception

Quadrats can be used to give an accurate picture of a habitat or ecosystem.

Sampling using a quadrat provides only a snapshot of a specific area at a specific time. To give an accurate picture, quadrat samples need to be taken over a long period of time to provide a more complete picture of a habitat or ecosystem.

Keywords

Population - A group of organisms of the same type, in the same place, is called a population.
Sampling - Sampling is a survey of plants and/or animals which provides information about the populations of organisms.
Quadrat - A quadrat is a square frame which is used to sample populations of plants or slow-moving animals.
Abundance - Abundance is the number of organisms of a species found within a habitat.