Sampling

Question 1

What are the 4 common ways of sampling to estimate the population?

Answer 1

Quadrants
Transects
Mark and recapture
Point

Question 2

What type of area is useful for Quadrant sampling?

Answer 2

direct count of organisms in smaller ‘samples’ of the larger study area and are placed randomly or in a grid pattern on the sample area, occurrences of organisms in the squares are noted

Question 3

When is Quadrant sampling used for? (3)

Impossible or impractical
Conjunction
Community composition

Answer 3

Used when direct counting of organisms is impossible or impractical

Used in conjunction with transects, but may be used singularly when the study area is relatively uniform

Well suited to determining community composition and features of population abundance; species density, frequency of occurrence, percentage cover and biomass (if harvested)

Question 4

What does Quadrant sampling estimate?

Answer 4

to estimate population abundance (number), density and distribution.

Question 5

Average Density =

Answer 5

Average Density = Total of no. of individuals counted / Number of quadrants x area of each quadrant

Question 6

What is Mark and recapture sampling useful for? (3)

Answer 6

Used for highly mobile organisms.

Determining total population density for highly mobile species in a certain area (eg.butterflies)

Movements of individuals in the population can be tracked (especially when used in conjunction with electronic tracking device)

Question 7

How is population calculated using mark and recapture?

Answer 7

Population is sampled by capturing as many individuals as possible, which are marked and released before being sampled again, after a suitable period of time.

Question 8

What is transect sampling useful for? (3)

Answer 8

Useful for determining species distributions and determine changes (trends) along an environment gradient (eg. altitude).

Are used for sedentary or slow moving organisms.

When placed randomly, they provide a quick measure of species occurrences.

Question 9

What are three different types of transect sampling?

Answer 9

different types (belt or line, continuous or interrupted)

Question 10

What type of organism are both quadrants and transects used for?

Answer 10

Both quadrants and transects are used for sedentary or slow moving organisms

Question 11

Total Population=

Answer 11

Total Population= No. of animals in 1st sample x No. of animals in 2nd sample/ No. of animals marked in 2nd sample

Question 12

What are 3 factors that can interfere with the accuracy of population estimates?

Answer 12

Time between recapture
Time (too long/ too short) - may not mix

births and deaths could occur.

Emigration and immigration

Question 13

What are 4 things to consider when using quadrant sampling?

Answer 13

Time consuming to do well.

plants and slow-moving animals are easily recorded, cryptic or moving animals need to be trapped or recorded using appropriate methods

Quadrant size must be appropriate for organisms to be sampled and information acquired.

Some disturbance if organisms are removed

Question 14

What is transect sampling?

Answer 14

Lines are drawn across a map and organisms occurring along the line are sampled.

Question 15

What are line transects? (2)

Answer 15

Species occurring on the line are recorded (all along the time or more usually at regular intervals).
They can be random or may follow an environmental gradient

Question 16

What are 4 things to consider when using line transects sampling?

Answer 16

Suitable for plants and immobile or easily caught animals

Disturbance in environment can be minimised

Species occurring in abundance may be missed

Time efficient

Question 17

What are belt transects?

Answer 17

measured strip located across the study area to highlight any transitions.
Along the belt quadrants are used to sample the plants and animals at regular intervals.

Question 18

What are some conditions of belt transects? (4)

Answer 18

Time consuming to do well

Suitable for plants and immobile or easily caught animals

Good chance of recording most or all species

Efforts should be made to minimise disturbance to environment

Question 19

What are 5 things to consider for mark and recapture sampling?

Answer 19

Time consuming to do well

Not suitable for immobile species, Used for highly mobile organisms.

Population should have a finite boundary

Period between samplings must allow for redistribution of marked animals in the population.

Marking should present little disturbance and should not affect behaviour

Question 20

What are two types of point sampling?

Answer 20

Random and Systematic

Question 21

What is point sampling?

Answer 21

Individual points are chosen on a map (grid reference or random numbers applied to a map grid) and the organisms are sampled at those points.

Mobile organisms may be sampled using traps or nets

Question 22

What is point sampling useful for? (1)

Answer 22

Determining species abundance and community composition. If samples are large enough, population characteristics (eg. age structure, reproductive parameters) can be determined

Question 23

What are 4 things to consider for point sampling?

Answer 23

Time efficient.

Suitable for most organisms.

Depending on methods used, disturbance to the environment can be minimised.

Species occurring in low abundance may be missed

Question 24

Density=

Answer 24

Density = population/area