S3 BGE BIOLOGY Part 1 BIODIVERSITY1C: Investigating Distribution of Organisms: Sampling

TechniquesYou will study the following topic at Level’s 3, 4 and 5. A. Biodiversity, Ecosystems & Investigating Abiotic Factors (L3/4/5) B. Biomes (L4/N4) C. Investigating Distribution of Organisms: Sampling

Techniques (L3/4/5) D. Identifying Organisms which have been Sampled: Keys (L3/5) E. Interdependence, Food Chains and Food Webs (L4/5) F. Energy in Ecosystems - Pyramids (L5) G. Interdependence -Niche & Biotic factors (L4/5)H. Impact of Population Growth on Biodiversity (L4/5)I. Impact of Natural Hazards on Biodiversity (L4)J. Conservation of Endangered Species (L4)

Sampling Techniques Learning OutcomesL3 Learning Outcomes: You should be able to…

o Give examples of sampling techniques.L4 Learning Outcomes: As well as L4 outcomes you should be able to…

o Use sampling techniques to include quadrats and quadrat analysis.o Use quadrats to estimate the distribution of an organism of a given area (e.g.

daisies in a field)L5 Learning Outcomes: As well as L3 & L4 outcomes you should be able to…

o Describe methods to make sampling techniques representativeo Describe examples to make sampling techniques reliableo Identify limitations and sources of error that might accompany the use of

sampling techniqueso Explain methods that can be used to limit the source of error

DEFINITIONS TO LEARN – MAKE ME A FLASH CARDBiological Definition

termSample A small representative part of a larger quantity(L5) Representative sampling

This seeks to choose components that match with key characteristics in the entire population being examined.

Quadrat A square frame of know area that is used for sampling the abundance and distribution of slow moving on non-moving organisms

Pitfall trap A sampling technique used to trap animals on the soil surface or in leaf litter.

Pooter A device used to collect small invertebrates from surfaces

Tree beating A sampling method which is used to collect animals that live on the leaves and branches of trees.

Sweep netting A sampling technique that is used to trap animals that live in long grass.

Pond netting A sampling technique which is used to trap animals that love in ponds and streams

(L4) Transect A sampling technique that involves placing quadrats at regular intervals along a line.

INTRODUCTIONBiologists often study biodiversity in an ecosystem. They want to gather information about which species are there, where they are found and the numbers in their populations (see patterns or trends occurring in habitats).

Representative Sampling. It is impossible to find and count every individual, so the scientist takes samples although there must be enough samples to make the results reliable.

(N5) Ensuring Representative Sampling. Sampling should include examples of all organisms in a habitat. Samples need to be taken using identical sampling apparatus. Samples need to be taken using identical methodology. Several samples should be taken, the larger the area the more samples

that need to be taken. Samples also need to be random.

SAMPLING TECHNIQUESThe sampling technique used depends on the type of habitat and the type of organism present. We will look at…

(L3) Quadrats Used to sample a variety of habitats, such as

grassland, moors and rocky shores. Used to sample plants, such as daisies or seaweed and non-moving or slow-moving animals

such as barnacles and whelks on a rocky shore.

Quadrats/Transects Pitfall traps Pooters

Tree beating Sweep netting Pond netting

Using a quadrat Quadrats should be placed randomly Examine and identify the organisms in the quadrat Count the number of the species you wish to study.

(L4) Using a quadrat to estimate the population of a sample (e.g. daisies).

1. Measure the area of the lawn2. Use the quadrats at random on several positions on the lawn3. Count the daisies in each quadrat and calculate an average4. Calculate the estimated total by multiplying the number by 4 (to give the

number per m2) and then by the area of the lawn.

(L5) – Limitations of using quadrats Organisms in the quadrat may be wrongly identified Organisms in the quadrat may be wrongly counted

(L5) – Reducing Error when using quadrats Use a key to ensure organisms are correctly identified Ensure all samples are taken with an identical method. e.g. If organisms

are only part in the quadrat make a rule for counting them like counting only the organisms that are at least half in the quadrat.

If it is noticed that organisms are in clusters, increase the number of samples taken.

(L4) Transects Transects involve placing quadrats at regular

intervals along a line. They can be used to investigate the effect of a

change in an abiotic factor (e.g. light intensity when moving from an open field into woods), and how this affects the distribution of an organism in an ecosystem

(L3,4,5) Pitfall TrapsUsed to sample small moving invertebrate animals that live in the soils surface and leaf litter.

Used to sample animals such as beetles, spiders, centipedes and woodlice A pitfall trap consists of a jar and a lid that is

buried in leaf litter.Using a Pitfall Prap Dig a hole in the ground and place a container in

it. Animals crawling around especially will fall it,

especially at night A cover over the top will stop the creatures drying

out, or from birds eating the trapped organisms. Traps should be left overnight and checked the

very next day to reduce the chance of predation in the trap.

L5) – Limitations of using pitfall traps

Top of the trap is not level with the soil surface stopping animals from falling into the trap.

Flying animals will fly out of the trap Animals that fall into the trap may not be there when it is emptied (climbed

out or have eaten each other) Animals may die of drowning.(L5) – Reducing Error when using pitfall traps Did hole deep enough and ensure that the top surface of the trap is level with

the soil surface Place a lid on top, this should be weighed down with stones. Empty regularly to prevent animals dying or eating each other. Place a few needle holes in the bottom of the container to allow rain to drain

(L4) Pooters Used to sample small insects and spiders. It is a small container with 2 tubes that works like an

insect hoover.

Using a Pooter The end of one tube is placed over the insect. The

researcher sucks on the other tube like a straw.

(L4/5) Tree beating Used to sample small organisms that live in

the branches and leaves of trees. It requires a stick and a white sheet (or

something to catch the organisms. A pooter can also be used to suck the organisms off the sheet.

Using tree beating Researchers hold a white sheet below the

branches of the tree to be sampled. A stick is used to hit the tree several times. The animals fall on to the white sheet and can be sucked up and collected

using pooters.

L5) – Limitations of using tree beating Animals may not fall onto sheet. Animals may move off the sheet before they are caught and identified. Animals may remain in the tree.

(L5) – Reducing Error when using tree beating Ensure that the white sheet is as large as possible. Do not work alone, have someone gently shake the organisms into the

middle of the sheet by raising at the corners. Before beating quietly observe the organisms on the tree, noting

especially any flying animals that can be seen on the tree.

(L3/4) Sweep Netting Used to sample small organisms that live in long

grass.

It requires a sweep net, a pooter, white tray and collecting jar.

Using a sweep net The sampler walks through the long grass, sweeping the net backwards

and forwards. The contents of the net are emptied onto a white tray. A pooter can be used to capture the animals before placing them in a

collecting jar.

(L3/4) Pond Netting (dipping) Used to sample some of the organisms that live in

a freshwater pond habitat. It requires a fine mesh net and a white tray or

bucket.

Using a pond netting The sampler pulls the net through the water using

a figure-of-eight motion. The contents of the net are emptied into a white

tray or bucket.