1. Life on Earth Chapter 18 – Sampling Techniques
National 5 Biology Unit 3
Life on Earth
Chapter 18 – Sampling Techniques

2. Section 3. 18 – Biodiversity and the Distribution of Life
By the end of this section you should be able to:
use and name a variety of sampling techniques to estimate the numbers of different organisms and environmental factors in a habitat or ecosystem.

3. 1. Quadrat What are quadrats used to sample?
Plants and very slow –moving animals

4. Method
Quadrats should be placed randomly so that a representative sample is taken.
The number of squares where the organism is present is counted.
Replicate to give a representative sample of the area.
Quadrats may also be used for slow moving animals such as snails/slugs. 1 2 5 4 3 6 7

5. What are the limitations?
Can only be used for stationary or slow-moving organisms.
It depends largely on human accuracy.
What are the common sources of error?
Incorrect counting
Non-random sampling

6. 2.Transect study
A transect study can be used to show how distribution of species varies across a habitat

7. How to….. Carry out a transect study
A transect is a line across a habitat or part of a habitat.
It can be as simple as a string or rope placed in a line on the ground.
The number of organisms of each species can be observed and recorded at regular intervals along the transect.
You could use a quadrat or pitfall trap to monitor the living things along a transect line

8. 3. Pitfall Traps What are pitfall traps used to sample?
Small invertebrate organisms living on soil surface.

9. Method
Bury a container with drainage holes, level with the ground. Traps can be baited.
Protect the trap from rain by placing a piece of raised wood or slate above the trap.
Leave the trap overnight.
Replicate to give a representative sample of the area.

10. What are the limitations?
Only traps ground fauna.
Easily disturbed
Often low catch per trap
Time required to bury traps
What are the common sources of error?
Incorrect identification
Predation occurs in the trap if left for too long.
Non-random sampling

11. Pitfall Trap
Used for: Animals which are active on soil surface and leaf litter.
Sources of error:
The numbers and types of animals may not be representative of the ecosystem as a whole.
How it works: Animals / Insects fall into the trap and are unable to climb out.
Source of error:
Birds may eat trapped animals.
Source of error:
Some animals may eat others.

12. 4. Tree beating
Tree beating can be used to sample small animals living in a tree.
A white tray or cloth can be used to collect the sample.

13. Tree Beating
How it works: A stick is used to give the branch of a tree a few harp taps. Small animals drop onto the tray which is held under the branch.
Used for: Insects and invertebrates which live in trees.
Source of error: Some organisms may miss the tray, drop of the edges or fly away.
Source of error: Some animals may not be dislodged by beating.

14. 5. Small Mammal Trap
Used for: Small mammals, e.g. Shrews, fieldmice, squirrels.
How it works: The trap is left on an animal track, filled with bedding and bait. Grain or dried fruit can be left both inside and outside the trap.
Source of Error: A drawback to using this method of trapping is that some animals are "trap-shy" whilst others become "trap-happy". This can pose a problem when estimating population size

15. 6. Tullgren Funnel
The Tullgren Funnel is an apparatus which helps to remove living organisms from leaf litter.

16. How to….. use a Tullgren funnel
Leaf litter is placed in a filter funnel.
The funnel is then held over a bottle containing a mixture of alcohol and water.
There is a piece of gauze present to prevent soil entering the liquid.

17. How to….. use a Tullgren funnel
Once the leaf litter has been placed in the funnel, the apparatus is put under a strong light for at least 2 weeks.
The soil dries out slowly and this encourages the living organisms to move downwards.
The living things can be examined using hand lenses or microscopes.

18. Tullgren Funnel
How it works: Tiny animals that live in the air spaces in the soil, move down and away from the hot, dry bright conditions created by the lightbulb and fall through the sieve.
Used for: Small organisms like beetles, millipedes and mites.
Source of Error: Soil sample may be too thick and may still contain many organisms at the end of the experiment.
Source of Error: Sieve mesh may be too fine and some animals fail to fall through.

19. 7. Sweep net
A sweep net can be used to sample invertebrates in the air or in low lying bushes or grass.

20. How to….. use a sweep net
To use a sweep net, move it back and forth gently through vegetation (long grass is ideal).
Try to swing the net in a figure-eight motion so that the open end of the net is always leading the way.

21. How to….. use a sweep net
After sweeping through the vegetation for a while, check to see if you have caught any creatures.
If so, close the net by gently pinching it shut near the top. One of the best ways to get creatures out of the net is to turn it inside out over a white cloth.
The creatures can then be picked up carefully and placed into jars for observation.

22. 8. Water Net Used for: aquatic invertebrates, aquatic mammals.
How it works: The net is moved rapidly through the water, catching animals which are quickly transferred to screw-top jars containing pond water.
Source of Error: When investigating the bottom of the pond, some animals may have been caught from the surface as the water passes through.
Source of Error: Small animals may escape through holes in the mesh.

23. 9. Pooters
A pooter allows you to gently remove a small invertebrate from its habitat so that you can look at it more closely.

24. How to….. use a pooter
Find a creature that you would like to examine more closely.
Put the gauze covered tube into your mouth.
Place the other end of the pooter to within a few centimetres of the creature.
Gently suck in so that the creature is vacuumed into the straw and up against the gauze.
Gauze

25. How to….. use a pooter
Place your finger over the pooter opening to ensure that the creature doesn't come out.
Place the pooter over a container, remove your finger from the end and gently tap the straw to release the creature.
Gauze

26. Pooter
11 November 2018