11.3 Sampling techniques

Question 1

Sampling animals: Pooter

Answer 1

• Used to capture small insects
• By sucking on a mouthpiece insects are drawn into the holding chamber via the inlet tube
• A filter before the mouthpiece prevents them from being sucked into the mouth

Question 2

Sampling animals: Sweep nets

Answer 2

• used to catch insects

- In areas of long grass

Question 3

Sampling animals: Pitfall traps

Answer 3

• used to catch small, crawling invertebrates such as beetles, spiders and slugs
• A hole is dug in the ground, which insects fall into.
• It must be deep enough that they cannot crawl out and covered with a roof-structure propped above so that the trap does not fill with rainwater - The traps are normally left overnight, so that nocturnal species are also sampled

Question 4

Sampling animals: Tree beating

Answer 4

• used to take samples of the invertebrates living in a tree or bush
• A large white cloth is stretched out under the tree
• The tree is shaken or beaten to dislodge the invertebrates
• The animals will fall onto the sheet where they can be collected and studied.

Question 5

Sampling animals: Kick sampling

Answer 5

• used to study organisms living in a river
• The river bank and bed is ‘kicked’ for a period of time to disturb the substrate
• A net is held downstream for a set period of time in order to capture any organisms released into the flowing water

Question 6

Sampling plants

Answer 6

• plants are normally sampled using a quadrat, which can also be used to pinpoint an area in which the sample of plants should be collected.
• Quadrats can also be used to sample slow-moving animals such as limpets, barnacles, mussels, and sea anemones
• there are two main types of quadrat:
  1) Point quadrat - this consists of a frame containing a horizontal bar. At set intervals along the bar, long pins can be pushed through the bar to reach the ground
  2) Frame quadrat - this consists of a square frame divided into a grid of equal sections. The type and number of species within each section of the quadrat is recorded
• To collect the most valid representative sample of an area, quadrats should be used following a random sampling technique.

Question 7

Measuring species richness

Answer 7

• Species richness is a measure of the number of different species living in a specific area
• To enable scientists to accurately accurately identify organisms, identification keys are often used
• These may contain images to identify the organism, or a series of questions, which classify an organism into a particular species basedon the presence of a number of identifiable characteristics

Question 8

Measuring abiotic factors

Answer 8

• Abiotic factors are the non-living conditions in a habitat
• They have a direct effect on the living organisms that reside there
• Examples are the amount of light and water available
• To enable them to draw conclusions about the organisms present and the conditions they need for survival, scientists normally measure these conditions at every sampling point
• Many abiotic factors can be measured quickly and accurately using a range of sensors, which are advantageous for a number of reasons:
  1) rapid changes can be detected
  2) Human error in taking a reading is reduced
  3) A high degree of precision can often be achieved
  4) Data can be stored and tracked on a computer